Author Topic: HP 4274A LCR Meter - mini teardown  (Read 20139 times)

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Offline Jay_Diddy_B

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HP 4274A LCR Meter - mini teardown
« on: March 02, 2014, 11:15:20 am »
Hi,

I have mentioned the HP 4274A LCR meter several times in my discussion of ESR Meters. I bought a second one today, so I thought I would share tips on buying this instrument and some pictures of the insides.

This LCR meter was manufactured in the 80s, by a joint venture between Hewlett Packard and Yogogawa. So you will see a little different style than HP equipment of the same vintage.

This is a high precision LCR meter 0.1% basic accuracy and 5 1/2 Digits of resolution. With option 001 or 002 you can measure capacitors with a dc bias voltage. The accuracy specifications are fairly complex. The accuracy becomes lower at high and very low impedances. I have attached a section from the Operators manual giving the accuracy.

The particular unit that I have photographed was manufactured in 1987.


Buying Guide

If you do a quick check on eBay you will see that most of the units are reporting Errors. This is quite normal  :D but can be used to your advantage to get a good price. The unit I am showing here I bought for $250.00


If you plug a unit in with nothing connected, you will get a display like this:



For it to work properly, the Lcur must be connected to Lpot, Hcur connected to Hpot and all four of the BNC shield connected together.

Here is a picture of the same unit with my home made Kelvin leads attached:



Also the Bias selector switch on the back should be set to OFF:



Jay_Diddy_B


« Last Edit: March 02, 2014, 11:18:29 am by Jay_Diddy_B »
 
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #1 on: March 02, 2014, 11:23:53 am »
Hi,

So let us have a look inside:



You can see the power supply section and the card-cage assembly.

This is a shot of the card-cage. The colour-coded ejector tabs are classic HP:



This is the A1 Range resistor and Null Detector Assembly:



With shields removed you can see some read relays and some high quality analog circuitry:



Here is close-up of the relays:



Jay_Diddy_B

« Last Edit: March 02, 2014, 11:28:46 am by Jay_Diddy_B »
 
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #2 on: March 02, 2014, 11:35:06 am »
Hi,
More pictures of the 4274A.
This is the A3 Power Amplifier Assembly, the circular black components are potted transformers:



This board is called the A4 Process Amplifier Assembly:



All these boards contain the Yogogawa Hewlett-Packard Logo:



The microprocessor board contains a Lithium battery to save the front panel settings in NVRAM:



Jay_Diddy_B
« Last Edit: March 02, 2014, 11:47:57 am by Jay_Diddy_B »
 
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #3 on: March 02, 2014, 11:43:26 am »
Hi,
To get repeatable accurate readings, the HP4274A uses a kelvin test fixture. The Kelvin test fixture can cost as much as the LCR meter.
Here is the 16047A installed on the 427A measure the Capacitance and ESR of small electrolytic:



Here is a close-up of the test fixture:



The inserts in the test fixture can be changed for radial and axial components:



Jay_Diddy_B
 

Offline rstoer

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Re: HP 4274A LCR Meter - mini teardown
« Reply #4 on: March 02, 2014, 12:04:30 pm »
Good information. Thanks.
 

Offline Vgkid

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Re: HP 4274A LCR Meter - mini teardown
« Reply #5 on: March 02, 2014, 12:08:44 pm »
Thanks for the teardown, where are the range resistors?
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #6 on: March 02, 2014, 12:23:51 pm »
Hi,
The range resistors are on the A1 assembly. Here is a photograph:



There are 5 covering 10, 100, 1K, 10K and 100K with dc and ac trims.

The resistors are marked TKD, this the Yogogawa influence.

Jay_Diddy_B
 

Offline Vgkid

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Re: HP 4274A LCR Meter - mini teardown
« Reply #7 on: March 02, 2014, 01:36:05 pm »
Im suprised to see that the resistors have a trim ability, i  figured that it would have tbrown off the freq response.
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #8 on: March 02, 2014, 01:47:53 pm »
Hi,

Here is the schematic from the manual:



The trimmers have a +/- 1% adjustment range. The trimmer capacitor are marked 'phase'. This is to make them resistive.

The 4274A is a 100 Hz to 100 kHz LCR meter. I also have the 4275A which covers the range 10kHz to 10 MHz. It would be interesting to see how different this section is for 10 MHz operation.

Jay_Diddy_B

 

Offline Vgkid

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Re: HP 4274A LCR Meter - mini teardown
« Reply #9 on: March 02, 2014, 02:24:03 pm »
It would nice to see a comparison between the two models. Im surprised they didnt just use one precision thin film resistor for each range. Also those are massive units.
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #10 on: March 02, 2014, 02:44:15 pm »
Hi,

One of the features of the 4274A is that you can adjust the test signal amplitude. The maximum current is 100mA. So this probably why there are some big resistors in the Range resistors.

Jay_Diddy_B

 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #11 on: March 02, 2014, 03:00:47 pm »
There is an interesting article on the 4274A and 4275A in the HP Journal:

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1979-02.pdf

Jay_Diddy_B
 

Offline dc101

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Re: HP 4274A LCR Meter - mini teardown
« Reply #12 on: March 02, 2014, 04:13:29 pm »
Nice pics man, looks in great shape.  Do you know the reasoning behind the potted transformers?  I've never seen them before.  Is it similar to how they have transformers in oil?
 

Offline Vgkid

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Re: HP 4274A LCR Meter - mini teardown
« Reply #13 on: March 02, 2014, 04:23:07 pm »
Going by the app note they should be for dc blocking in the signal path.
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Offline casinada

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Re: HP 4274A LCR Meter - mini teardown
« Reply #14 on: March 02, 2014, 06:50:22 pm »
Looks that those PCBs are pre silk screen days. All the labeling is etched on the PCB just like the circuit traces.I wonder who was the first to implement silk screens on the PCBs :)
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #15 on: March 02, 2014, 10:18:28 pm »
Looks that those PCBs are pre silk screen days. All the labeling is etched on the PCB just like the circuit traces.I wonder who was the first to implement silk screens on the PCBs :)

This unit was described in the HP Journal in 1979. The schematics are definitely hand drawn. There is a high probability that these boards artworks were generated without a CAD system. I see some evidence of the boards being taped.

Before CAD systems were used, the process of designing a board:

1) The artwork was drawn with red and blue pencils. By tradition red was used for the solder side and blue was used for the component side.

2) Pre-cut paper donuts were used for the pads. Bishop Graphics was one of the main suppliers of these pads. The pads were placed on a sheet of Mylar.

3) A second sheet of Mylar was then placed on top. Red and Blue tapes were then run between the pads.

4) This artwork was normally generated twice actual size.

5) The artwork was then reduced to 1:1 with a process camera. Coloured filters were used to separate the top and bottom layers.

6) The boards were then fabricated from the films.

Generating a silkscreen layer was done, but it was time consuming.

Jay_Diddy_B

 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #16 on: March 03, 2014, 03:01:33 am »
It would nice to see a comparison between the two models. Im surprised they didnt just use one precision thin film resistor for each range. Also those are massive units.

Vgkid,

Here are a few pictures from the 4275A, the 10 kHz to 10 MHz model.

Front Panel
Here is a picture of the 4275a measuring the capacitance and ESR of a small electrolytic capacitor:



The 4275A agrees with the Jay_Diddy_B ESR meter adapter  :-DMM



So the 4275A must be good  :-+

Overview

This shows a similar construction to the 4274A. This unit has option 001, 0-35V dc bias source:



A1 Reference resistor assembly

With the shields in place:



Without the shields:



This is a close-up of the reference resistors. The resistors are similar to the resistors in the 4274A. plastic tubing has been used space the resistors of the ground plane. There is also a more complex circuit for ac trims:



Jay_Diddy_B




« Last Edit: March 03, 2014, 03:07:33 am by Jay_Diddy_B »
 

Offline Vgkid

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Re: HP 4274A LCR Meter - mini teardown
« Reply #17 on: March 03, 2014, 03:11:33 am »
Thanks for  the added pics.
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Offline dc101

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Re: HP 4274A LCR Meter - mini teardown
« Reply #18 on: March 03, 2014, 05:33:48 am »
Going by the app note they should be for dc blocking in the signal path.

Sorry, I should have been more clear.  I was curious what the potting was for on the transformers?  Vibration?  Heat?  They look pretty cool, I thought they were massive caps at first.
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #19 on: March 03, 2014, 07:09:48 am »
Sorry, I should have been more clear.  I was curious what the potting was for on the transformers?  Vibration?  Heat?  They look pretty cool, I thought they were massive caps at first.

I don't much about the inside of the transformer.

It would make sense if they were toroidial cores. If they are toriodial transformers the plastic cup can be used to keep all the leads aligned.

The potting compound would seal the transformer from moisture.

It would prevent the transformers from being microphonic. This would prevent vibrations, especially from the fan, interfering with the measurements.

I am sure it is not for power dissipation, these are low power signal transformers. 

Jay_Diddy_B
 

Online BravoV

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Re: HP 4274A LCR Meter - mini teardown
« Reply #20 on: March 03, 2014, 01:41:46 pm »
The Kelvin test fixture can cost as much as the LCR meter.

Few years ago I was offered this exact fixture for about $150 nib, but I was not interested since I thought I need to have the LCR meter 1st which is hard to get. I guess I could make few pennies by reselling it at fleebay if I bought it ?
 

Offline dc101

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Re: HP 4274A LCR Meter - mini teardown
« Reply #21 on: March 03, 2014, 01:46:08 pm »
The Kelvin test fixture can cost as much as the LCR meter.

Few years ago I was offered this exact fixture for about $150 nib, but I was not interested since I thought I need to have the LCR meter 1st which is hard to get. I guess I could make few pennies by reselling it at fleebay if I bought it ?

Maybe, $150 seems to be what they're selling for these days.  There's a couple people offering a buy it now price for more than $300, so I suppose it depends on how long you can wait.  Jay's is in really good shape so something it that condition might go for slightly more.
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #22 on: March 05, 2014, 12:53:58 pm »
The Kelvin test fixture can cost as much as the LCR meter.

This was an approximation. There are some fixtures on eBay for $150.00. These are only include one of the three sets of inserts. You have to be lucky or spend a lot of money to get one with all the inserts.

The BNC connectors on the front of the HP LCR meters are spaced 22mm apart. This spacing has been adopted by other manufacturers. You can also by other test fixtures like this one for around $60.00.



The point I was making, an LCR meter with the fixture is worth considerably more than an LCR meter without a fixture.

You can find many examples of Kelvin leads like these on eBay:



These have to be modified to work with the HP 4274A and HP 4275A. The shields have to be connected together at the clip end of the cable:



Jay_Diddy_B
« Last Edit: March 05, 2014, 12:55:38 pm by Jay_Diddy_B »
 

Offline CaptnYellowShirt

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Re: HP 4274A LCR Meter - mini teardown
« Reply #23 on: March 05, 2014, 06:24:10 pm »
Awesome teardown!

I was under the impression that the HP meters used the "Four-terminal pair" (4tp) DUT configuration. Its similar to the shielded four-terminal method, and both leads will function when hooked up. The difference with the pair method is current is carried on the shields of the Hcur and Lcur terminals, while the Hpot and Lpot terminal shields are just that, shields.

Check me on this though...
 

Offline TinkerGDS

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Re: HP 4274A LCR Meter - mini teardown
« Reply #24 on: January 02, 2017, 05:08:04 am »
I found this thread very interesting.  I just picked up a 4275A in very clean condition.  When I first turned it on I initially got the battery error.  I suspect the A9 battery is dead.  I want to replace it, but the service manual has no information on what type of battery this is.  Also, the service manual schematic shows the battery as 2.8v, but the battery on the board is 3.9v.  I see in your A9 board pic, your battery is also an ElectroChem.  Is your batter also the BCX-72-AA (3B64)?  I removed the battery and found out it is a Li-Ion battery.  Has anyone replaced these with a compatible type?
« Last Edit: January 02, 2017, 05:45:26 am by TinkerGDS »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #25 on: February 04, 2017, 08:30:07 pm »
Hi all,

I bought a HP 4274A. It used by an University. The original option labels has been removed I think. How can I check, what options installed?
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #26 on: February 04, 2017, 09:32:12 pm »
Hi,

Here is a list of possible options:


From the picture, you have:

001 or 002 I can't tell from the picture, but you do have the connector to control the internal bias supply.

003 It is hard to tell. It isn't an important option.

004 you can tell if you power it up and step through the test frequencies.

101 you have, because there is an HPIB connector.

The other options are not important.

The green box is a modification somebody has done. The labels may be under the box.


Regards,

Jay_Diddy_B
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #27 on: February 09, 2017, 08:51:32 am »
Thank you!

I know more when the LCR meter arrived. I give you the 100. thanks! :D

I got a picture, looks like the meter working fine.
« Last Edit: February 10, 2017, 04:56:03 am by MateKrisz »
 

Offline mightyohm

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Re: HP 4274A LCR Meter - mini teardown
« Reply #28 on: August 05, 2017, 09:12:00 am »
Can someone share photos of their modified Kelvin clips?  I'm wondering how to do this gracefully since the two alligator clips now need to be tethered to each other.
 

Offline Inverted18650

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Re: HP 4274A LCR Meter - mini teardown
« Reply #29 on: December 16, 2017, 01:01:02 pm »
I realize this thread is old but wanted to leave this here for anyone who is in the market or may have one of these as well. I am not trying to high-jack the thread and cannot say enough thanks to Jay-Diddy for his work here. I am currently reworking my cheap-o ebay Kelvin leads according to his diagram and that video will be up soon. If anyone has any pointers for me, please feel free to comment here or on the video. Many thanks.

video:

Update: I probed all the Unknown BNC connectors on the front panel and checked to see if they all bodies, not the center line, go to ground. The H CUR (4th from left) does not, the other the have continuity. The BNC ground for 'H CUR' goes to board 3 from the left. Its the one with orange tab, via the mini-BNC cable. Does anyone know if this is normal, or could that be the Error 4 fault?

Update 2: I made my own BNC cables and followed the flow chart from the service manual, page 8-33, and checked the voltage on A6-TP1 and adjusted it up to 500mV. I am not certain that the adjustment fixed it Error 4, or if it was just the cheap-o leads, but the meter is working now and I am stoked. Many thank Mr. Diddy!
« Last Edit: December 17, 2017, 06:45:28 am by Inverted18650 »
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #30 on: December 20, 2017, 06:30:40 am »
Hi,

You will get error 4 if the shields on the cables are not connected together at the test end of the cable.
There is a diagram in this message:

http://www.eevblog.com/forum/testgear/hp-4274a-lcr-meter-mini-teardown/msg399732/#msg399732

If you take a piece of wire and connect all four shields on the front panel BNC connectors together error 4 should disappear.

Regards,
Jay_Diddy_B
 
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Offline Inverted18650

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Re: HP 4274A LCR Meter - mini teardown
« Reply #31 on: December 29, 2017, 02:19:25 pm »
This was exactly my issue and the meter is now working “a treat” as Dave would say. Thank you Sir for the reply and the project you posted.
 

Offline cncjerry

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Re: HP 4274A LCR Meter - mini teardown
« Reply #32 on: December 30, 2017, 07:30:24 am »
might as well kick this thread all the way open.  I have the version with the  comparator on it, the HP 4262A.  Once you have the kelvin style leads setup the meter is very accurate.  I had to replace the front panel banana jacks as mine were so corroded they wouldn't tighten down on the shorting bar causing the error previously mentioned.  It took me a few hours to track it down as it looked like the shorting strap was on the jacks and they were tight.  One of those dumb errors that takes forever to fix.

I also have the Agilent handheld, U1733C I think, bought it here when they were on sale for a good price, and the handheld does a great job. I've been thinking of retiring the 4262A but I sort of like it for sorting caps.  The comparator is really handy once you calculate the range you need.

Overall, the biggest challenge other than the power supply caps is all the front panel connectors and cables, at least on the 4262a.  My last bit of advice in this area is that the handhelds like the U1733C will usually be more convenient, just about as accurate as at least the 4262A, and have some of the more common frequencies needed for testing ESR.

~Jerry
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #33 on: May 27, 2018, 05:18:39 am »
Hi,

I have a 4274A, I bought long time ago, but just now wake up the unit.
I made a little video about what do when starting. First time ok, but under 0,6 osc level with x1 multiplier send the error4 messages.
It is normal? Or not?

video:

Second thing, that I compared the original wiring schematic with what I found in this topic. I made a picture when see the different things.
My question that need the red pinned shorts?

Thanks!

Regards,
Krisztian

« Last Edit: May 28, 2018, 08:02:07 pm by MateKrisz »
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #34 on: May 29, 2018, 04:40:54 pm »
Hi,

I have a 4274A, I bought long time ago, but just now wake up the unit.

Snip ...

Second thing, that I compared the original wiring schematic with what I found in this topic. I made a picture when see the different things.
My question that need the red pinned shorts?

Thanks!

Regards,
Krisztian



Yes, you need the connections marked with red dots. This means connecting all the shields together. When you connect the shields together it will remove error 4.

Regards,

Jay_Diddy_B
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #35 on: May 30, 2018, 04:36:07 pm »
Hi,

Thank you your answer! I try it.

Thanks!

Krisztian
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #36 on: June 02, 2018, 03:50:44 am »
Hello members of the forum!
I did prophylaxis to my HP4275A and decided to add photos for you.
Later, when I'll make the following photos, I will definitely upload photos for you with six modules.
The device has worked more than 25 years.
There were no problems.

Sincerely, 3G57.
p.s. I made a replacement for the bios battery twice. Last time in 2013.



























































When You doing selftest follow this (video hasn't this):



TEST LEADS





























The device is very sensitive to changes from the factory TEST FIXTURE.
When making their cords, the parameters * L * * C * * R * of the factory ones must be taken into account.
(Electrical capacitance of the device, cable inductance, resistance of conductors.)
These three parameters are necessarily present in any installation.
Otherwise, the input circuit of the device will be unbalanced and it will not be able to adjust the input circuit during calibration.
The input is unbalanced.
The test will not be passed. The measurements are distorted!

!!!  SELF-TEST only with TEST FIXTURE 16047A.
on others the test will not be passed! There will be errors!

OPEN TEST enabled mode * C *    BIAS *0FF*



SHORT TEST enabled mode * R *   BIAS *0FF*



WRONG. SHORT TEST when C mode is on
there are errors !!!!   BIAS *0FF*





A5 A-D CONVERTER 04275-66505







A4 PROCESSOR AMPLIFER 04275-66543

























A3 POWER AMPLIFER 04275-66503





A2 MODULATOR 04275-66502









A1 RENGE RESISTOR & NULL DETECTOR 04275-66501






















16023B BIAS CONTROLLER


















Best regards, 3G57
« Last Edit: June 06, 2018, 08:45:16 pm by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #37 on: June 02, 2018, 10:26:37 am »
Hi all,

I made simple 4 wire for my meter. I followed the 4T configuration. It is ok? Picture attached.
On the display always reading ERR 4 messages. I started check the voltage on the test points.
Here is the results:
8-16 page:
Initial settings, (Freq- 1kHz, Multiplier X1 etc, Osc Level: full cw) adjusted.
A6 TP-1 - Sin 500mVrms - OK
next step:
A3 TP-3 - Sin 3,3 Vrms- Exactly not ok. I measured 1Veff and I can change this value with osc level and multiplier. Is misprint in the service manual?
next step:
Wavefrom at high terminal: it's ok
next
Does OP-1 - Yes
next
Is A5 adjusted ? - I'm here now.

What do you think about the handmade "fixture"? The wiring good?

Regards,
Krisztian
 

Offline precaud

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Re: HP 4274A LCR Meter - mini teardown
« Reply #38 on: June 03, 2018, 12:47:44 am »
I made simple 4 wire for my meter. I followed the 4T configuration. It is ok? Picture attached.

What do you think about the handmade "fixture"? The wiring good?

I don't think it is the cause of your ERR 4 message, but you don't need to connect the BNC shields at both ends of the cables. They just need to be joined at the end near the clips. That moves the reference ground plane out near the connectors.

Also, it would be easier to use if you only had one alligator clip on each side, and connect the inner conductors to one clip on each side. After doing Open/Short compensation, there will be no difference in accuracy, especially within the 100kHz frequency range of the 4274A...
 

Offline bugi

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Re: HP 4274A LCR Meter - mini teardown
« Reply #39 on: June 03, 2018, 01:05:58 am »
... but you don't need to connect the BNC shields at both ends of the cables. They just need to be joined at the end near the clips. That moves the reference ground plane out near the connectors.
There has been pics in this thread both with and without shield connections at the device end. To me, it makes more sense to have them without (i.e. only the clip ends connected). (Like in this http://www.eevblog.com/forum/testgear/hp-4274a-lcr-meter-mini-teardown/msg399849/#msg399849)
Also, the ground "reference" or "plane" should be out there either way, but according to one of the pics, the clip end connection allows balanced currents in the drive cables. That is, not just one current going through positive drive center cable and the same current returning in the negative drive center cable, but also opposite currents in the drive cable shields'. (Whatever benefit that might give...)
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #40 on: June 03, 2018, 01:28:03 am »
I think I need to check here
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #41 on: June 03, 2018, 05:26:29 am »
Hi all,

Thanks 3g57 the amazing photos! I ordered the B+K TL89F1 fixture, somewhere I saw that is working with this model.
I have the 04274-66523 DC Bias +100V board. I quick checked at A23 TP1, and A11 5R and here is nothing. :/

Krisz
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #42 on: June 03, 2018, 05:34:20 am »
Hello members of the forum!
I did prophylaxis to my HP4275A and decided to add photos for you.
Later, when I'll make the following photos, I will definitely upload photos for you with six modules.
The device has worked more than 25 years.
There were no problems.

Thank you so much for the details & superb photos.  :-+  :clap:

Photos saved locally.  :P
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #43 on: June 03, 2018, 05:50:31 am »
OK! :-+
Later I will give the following.
« Last Edit: June 03, 2018, 05:55:25 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #44 on: June 03, 2018, 11:43:29 am »
... but you don't need to connect the BNC shields at both ends of the cables. They just need to be joined at the end near the clips. That moves the reference ground plane out near the connectors.
There has been pics in this thread both with and without shield connections at the device end. To me, it makes more sense to have them without (i.e. only the clip ends connected). (Like in this http://www.eevblog.com/forum/testgear/hp-4274a-lcr-meter-mini-teardown/msg399849/#msg399849)

Yes, that diagram shows them connected at the "clips" end. That is also as it has been specified in the HP Impedance handbooks.
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #45 on: June 04, 2018, 01:30:58 am »
Krisz look at two places. I have indicated to you.
I had a distrust of mine and I corrected it.
Take the lens!
« Last Edit: June 04, 2018, 01:35:58 am by 3g57 »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #46 on: June 04, 2018, 04:40:21 am »
Krisz look at two places. I have indicated to you.
I had a distrust of mine and I corrected it.
Take the lens!
Hi,
Ok, I check it now. A check the voltages at the TP points too. Do you replaced the old electrolytic capacitors in yours?
Krisz
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #47 on: June 04, 2018, 04:54:15 am »
No, I did not change the capacitors.
I'm not ready for this yet.
After the replacement it is necessary to do the calibration.
Time is not enough.
He's still in the norm.
I will make a replacement.
The connectors in my power supply unit were undermined.
You should watch this!!
I need to make a test card for TP control.
p.s. Krisz! Take a photo of your module at 100v.
Lay out on the page!
« Last Edit: June 04, 2018, 05:09:49 am by 3g57 »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #48 on: June 04, 2018, 06:20:11 am »
Hi,
I resoldered the all connection on power board and measured the voltages of TP points, picture attached.
I have an extension for ext DC bias:


Inside:



100V DC Bias





P.s. I thinking about the extension. Well I bought from US, and a University used before. The picture about the extension taken is US and you see that INT Bias ON. It is worked over there. In Hungary, I made the handmade "fixture" and first time worked for me, but several hours later starting the ERR4 messages. I think maybe sometimes work the INT Bias sometimes not, and they used over there external BIAS supply too. What do you think?
« Last Edit: June 04, 2018, 06:49:42 am by MateKrisz »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #49 on: June 04, 2018, 06:58:11 pm »
Hi! Krisz. This is your module.
15 left contacts + 15 right contacts x2 side.
I have 18 + 18.
You need to measure the stresses where I showed below in the attachment.
I think I was not mistaken.
I did not look at 15 right-wingers. They are in your module 100v.
Replace R3 with multi-turn.
Set -5v STD.!!!!!!

+ 12v and -12v should be with great accuracy.
This is a bipolar supply of operational amplifiers.
Otherwise, it will be difficult to do correction TP.
-3G57

p.s. My.



To your question:
Internal DC-BIAS 35v & 100v  will only work when
connected to external control (16047A TEST FIXTURE) !!!
This is a kit.
The indicator (LED) on the front panel will be on!
In this case, you should not turn on the calibration mode !!!
Calibrate the instrument. * OFF * S4 on the rear panel.
For your 100v module (04274-66523), you need
corresponding TEST FIXTURE (not 35v)!!!
To use an external 200v to power,
too, a corresponding TEST FIXTURE (not 35v)!!!

According to your picture.  Perhaps they used external
input 35v for leak testing  electrolytic
capacitors But this is dangerous for the entrance of the device.
When testing a capacitor of high capacity and  voltage
there is a possibility of its discharge potential at the input terminals.
Before testing, it is necessary to discharge the capacitors !!!
Otherwise, the spark and the possibility of damage

- 04274-66523 DC Bias + 100V board
used to test the capacitance of transitions in transistors.
This is done on this device.













(draw a circuit board that's in the box! Interesting!
In the box must be installed required voltage and current limited to 100mA)

Check the test signal level and frequency on the
control points of quartz resonators.
Perhaps the frequency has gone.
When you rotate the oscillator knob, the signal is captured




« Last Edit: June 05, 2018, 04:15:00 am by 3g57 »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #50 on: June 05, 2018, 05:06:28 am »
Hi,

Thank you the useful informations! I measured the power board output voltages, and I found some not normal voltage value. The left side is working good, but the +44, -44, -22 exactly not. I used the common GND point.




I ordered a B+K TL89F1 fixture. (https://hu.mouser.com/ProductDetail/BK-Precision/TL89F1/?qs=CjgjetG5vV4ukiCCEHhtpw==)
It can:
Test fixture for convenient testing of axial and radial leaded type components.

Frequency: DC to 10MHz
DC Bias:+/- 40V peak max (AC+DC)
Operating Temperature: 0 to 40 degrees C
Terminal Connection: BNC to 4 terminal insertion slots (radial or axial)

Well, yesterday I bought on the eBay a 16023B bias controller ( https://www.ebay.com/itm/HP-Agilent-Keysight-16023B-bias-controller/273240404664 )

I think with bias controller, they can work together the 100V bias board and the 40V fixture.

I measured the osc level and freq on the H cur BNC socket, and seems to be ok.

I attached a catalog sheet from '79 catalog.
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #51 on: June 05, 2018, 05:14:29 am »
Hi! do not rush into conclusions about the common wire
for -44 and +44. At them it another. Look at the diagram.
You can measure the voltage across the capacitors С5,С6.
_____________
question:
Measured with load?
Measure under load on capacitor contacts.

I marked GND & W3 Pin 2,3



Only measure with load  All points !!!!
« Last Edit: June 05, 2018, 05:46:28 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #52 on: June 05, 2018, 05:44:30 am »
Hi,

Yes, now I see the GND. I remeasured but nothing changed.  :/
Yes I measured with load, the fully unit is working.

« Last Edit: June 05, 2018, 05:46:12 am by MateKrisz »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #53 on: June 05, 2018, 05:50:25 am »
Slightly understated +12 and -12.
Will pass through the tires and the board will be even smaller.
Better in the power supply a little more but always symmetrically !!!
« Last Edit: June 05, 2018, 05:53:34 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #54 on: June 05, 2018, 05:56:12 am »
Yes, but I have the original R3 and I wanna replace to multi-turn.
Do you have idea why bigger the +-44 and -22 voltages?
Before CR-13, CR-14 I measured 49,2 AC Volts. How?
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #55 on: June 05, 2018, 06:01:52 am »
Check the AC switch on the rear panel
device power supply voltage? 220/240 ???

If you have 220AC, then you can safely put
on 240VAC. Just do not make a mistake!
Then measure.

Take off R3.
Measure the resistance !!!
On the new install the same.
Only then install it!
« Last Edit: June 05, 2018, 06:09:24 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #56 on: June 05, 2018, 06:12:35 am »
Yes of course, because when arrived from US the first thing was that I swicthed from 120 to 220V.
I have transformator I can use it 120V too.

 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #57 on: June 05, 2018, 06:16:38 am »
A transformer is not needed.
Switch to 240VAC and measure now the voltage points!
___________________________
« Last Edit: June 05, 2018, 06:39:35 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #58 on: June 05, 2018, 06:41:46 am »
I switched up to 240V the primer. OMG what a collection!!! :D Grats! :)
Try it on 120V? Maybe....
Well the results:

« Last Edit: June 05, 2018, 06:45:23 am by MateKrisz »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #59 on: June 05, 2018, 06:44:56 am »
Is the tension closer to the truth?
Check the work for a mistake! Er4
« Last Edit: June 05, 2018, 06:47:21 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #60 on: June 05, 2018, 06:47:59 am »
Yes, but +44 and other still high yet. Try on 120V?
ERR 4 message still flashing yet.
« Last Edit: June 05, 2018, 06:52:08 am by MateKrisz »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #61 on: June 05, 2018, 06:52:47 am »
Do not need a transformer.
This is already normal. :)

Wait for the purchase!
Then you will look.
Your entrance is open.

But still there is a problem!

Show more download videos.
At the same time, reduce the frequency to 10 kHz  x1
« Last Edit: June 05, 2018, 07:04:06 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #62 on: June 05, 2018, 06:54:42 am »
The +12V on +44 it is normal? :)
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #63 on: June 05, 2018, 07:00:35 am »
Ok, I wait both item. I hope will arrive in this week.
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #64 on: June 05, 2018, 07:22:59 am »
It's late. I'm going to sleep.
Best regards!
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #65 on: June 05, 2018, 07:30:17 am »
Ok, I still bundle the tools. Thanks your help! Good night! :)

 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #66 on: June 06, 2018, 08:24:13 pm »
I wrote that the HP4275A worked without problems. And here is the problem. Breached the resolution of switching voltage 16023B BIAS CONTROLLER. The fault wasOctal D Flip−Flop with Clear. After the replacement, the normal work resumed.



3g57
« Last Edit: June 06, 2018, 10:26:23 pm by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #67 on: June 07, 2018, 04:54:15 am »
MateKrisz! Hi!
Have you drawn a scheme of a secret casket? :palm:
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #68 on: June 07, 2018, 04:58:38 am »
Hi,

I hope all well with your 4275A!
My packages on the way, I waiting... :) What asking?
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #69 on: June 07, 2018, 05:14:33 am »
Everything is normal! LS - the series is weak. Unreliable.
ALS is much better.
Therefore also has died.  ;)
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #70 on: June 07, 2018, 05:21:49 am »
It is not sounds good, can I help you? :)
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #71 on: June 07, 2018, 07:21:43 am »
MateKrisz! I will draw Extender boards.
I think the HP4275A needs to be calibrated.









3g57
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #72 on: June 07, 2018, 07:37:28 am »
Hi,
It is interest, never seen before.  And what extend with this board?
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #73 on: June 07, 2018, 07:46:07 am »
This was done for NIKON equipment.
I will do this for the HP4275A.
This one does not fit.

3G57
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #74 on: June 07, 2018, 07:43:14 pm »
MateKrisz! Hi!
Have you drawn a scheme of a secret casket? :palm:

Yes, I will send you at tonight.

Krisz
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #75 on: June 08, 2018, 05:34:30 am »
Hi,

Here is the schematic of the little box. The bigger diode type is not clean for me. I hope it helps you:









Krisz
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #76 on: June 08, 2018, 06:15:29 am »
 1.5SE36A (NTE4940 analog)
Overvoltage Suppressor 36V .
Protection against higher voltage.
Suppressors are usually used in impulse power supplies.
They protect against voltage surge.
Installed on the primary winding of the transformer.
As I wrote the box gives a certain voltage
and limits its current to 100mA.

3g57
« Last Edit: June 08, 2018, 06:29:29 am by 3g57 »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #77 on: June 08, 2018, 06:23:25 am »
Ok, thanks! :)
The fixture will arrive tomorrow! :)
« Last Edit: June 08, 2018, 06:52:35 am by MateKrisz »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #78 on: June 08, 2018, 09:27:49 pm »
Hi,

The fixture arrived, and I could not wait,  I opened the box and installed the fixture. I followed the open and shorts test procedure, but not succeed.  ERR 1 and then ERR 4 flashing :/



Krisz
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #79 on: June 08, 2018, 10:44:42 pm »
Hi! Krisz!
I did not know that you would buy the option 16023B BIAS CONTROLLER. :'(
You hurried. You should have bought PM2811 for this price.
You would have got one more device and it was run by DS BIAS!
I work this way.
How to calibrate PM2811/PM2813 it I described here!

http://www.eevblog.com/forum/reviews/phillipsfluke-pm2811-power-source/msg1322150/#msg1322150

He has a discreteness of 1mV. Learn.
It allows you to limit the current.












3g57 ;)

p.s. I uploaded your HP4274A circuit yesterday.
Has studied. You have a problem in A3.
I will write later. You need to do measurements on A3.
« Last Edit: June 09, 2018, 12:03:01 am by 3g57 »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #80 on: June 08, 2018, 11:36:40 pm »
  ERR 1 and then ERR 4 flashing

 :palm:

It is necessary to make measurements. :-DMM

I think you have a problem with the signal level on A3.
You need to check:
1. Input BNC connectors. Cable from them to leak
2. R28 - loss of contact or poor contact.
3. Voltage to CR1, CR18
4. In А3 - ТР2, ТР3,
5. key Q2,3,4
6. the key Q10,11,12,13,14
7. carefully U5. Comporator LM339P she manages the keys.
you need to get passport modes on T3 and T6.
Remember that the common points are different!
I hope that the power supply voltage of the module is normal.



The following models did not use an operational amplifier. The discrete elements were installed.
Perhaps this is more reliable.

« Last Edit: June 12, 2018, 02:39:32 pm by 3g57 »
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #81 on: June 09, 2018, 03:45:38 am »
Hi,

Thank you! I now measure the suggested areas.
I come back later with values.
Krisz
 
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Re: HP 4274A LCR Meter - mini teardown
« Reply #82 on: June 09, 2018, 03:50:28 am »
Hi,

Thank you! I now measure the suggested areas.
I come back later with values.
Krisz

Your x10 AMP is not working well.
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #83 on: June 09, 2018, 04:03:23 am »
On A3 board?
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #84 on: June 09, 2018, 04:05:23 am »
« Last Edit: June 09, 2018, 04:07:48 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #85 on: June 09, 2018, 04:51:28 am »
Well, I check the list, here are the results:

R28 10 ohm - OK
A3 TP2 34mv
A3 TP3 -7mV

It is interesting, I just checked.
A6 TP1 -10mV
A6 TP2 -2mV
A6 TP3 +2,5V

A5 TP1 +5,97V
A5 TP2 -5,97V

« Last Edit: June 09, 2018, 04:54:47 am by MateKrisz »
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #86 on: June 09, 2018, 05:03:12 am »
You wrote to me that with the oscillator is normal! :-\
Now go from the oscillator! |O
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #87 on: June 09, 2018, 05:04:53 am »
Yes, it was normal and worked fine, but now I just checked and you see that what measured. :/
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #88 on: June 09, 2018, 05:07:04 am »
Yes, it was normal and worked fine, but now I just checked and you see that what measured. :/

Do not understand.
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #89 on: June 09, 2018, 05:15:08 am »
I checked the test signal on H Cur with the scope. Pic attached. Here is the test signal nice sin wave and the levels is ok.
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #90 on: June 09, 2018, 05:26:15 am »
Open the manual and see FIGURE 8-31.
Follow the path.
DSA2 is a TRD DECODER
Bottom left.
« Last Edit: June 09, 2018, 05:30:29 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #91 on: June 09, 2018, 05:36:28 am »
OK :)
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #92 on: June 09, 2018, 06:22:10 am »
Sorry, first time I made a bad measurement :/
Well, the correct is:

R28 - 10 ohm - OK

A3 TP2 3V rms - 1 kHz
A3 TP3 1V rms
A3 TP1 500mV rms (it should be here 7Vpp), replace T3 T1? -> http://hu.farnell.com/murata-power-solutions/76602-1c/transformer-pulse-1-1-1/dp/1087810


A6 TP1 500mV rms
A6 TP2 600 mV rms

I hope it helps.
Krisz

 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #93 on: June 09, 2018, 06:51:42 am »
 TP1, TP4?
Are the transformers identical?
swap places. look!

A6 TP2 = 1.5VP-P is the norm.
see above FIGURE 8-40.
« Last Edit: June 09, 2018, 07:08:38 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #94 on: June 09, 2018, 07:02:18 am »
at A3 TP4 should be 3Vpp but there is nothing.
I think need replace the A3 T2 too. This is the correct replacement: http://hu.farnell.com/murata-power-solutions/76602-1c/transformer-pulse-1-1-1/dp/1087810
« Last Edit: June 09, 2018, 07:09:42 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #95 on: June 09, 2018, 07:20:17 am »
Try it!
check again the sigils A6.output A2
You have a problem in a weak signal.
You rotate the handle of the oscillator to the left and from the middle you clean it completely.
« Last Edit: June 09, 2018, 07:26:48 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #96 on: June 09, 2018, 07:27:10 am »
Ok, I check with the Figure 8-40.
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #97 on: June 09, 2018, 10:06:51 pm »
Krisz! Hi! Make yourself on the HP4274A.
I do not have a good file for this. I made an example for the HP4275A.
You will be more clear.
Do not confuse RMS and P-P with measurements. You're close with the problem.
Do not rush.







Observe such conditions with respect to HP4274A.
They are different from you.



3g57
« Last Edit: June 09, 2018, 11:31:48 pm by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #98 on: June 10, 2018, 12:43:28 am »
Hi,

Yesterday I had a small problem with my scope. I fixed it first.
Today I rechecked the following test points, I followed the charts.

Figure 8-16
A6 TP1     500 mVrms - OK
A3 TP3     3,3 Vrms - I measured 1 Vrms

Go to A3 troubleshooting Figure 8-31

A3 TP2     8,4Vpp - OK
Controlled by vernier? - yes
A3 TP3     All amplitudes (0.01 , 0.1 , 1 , 5 Vrms) - All OK
A3 TP4     3 Vpp - I measured 1.6 Vpp
Check A3T2 transformer

I checked to the A3 TP1 7Vpp - I measured here 1.6 Vpp
Check A3T1 transformer

It is possible that both transformers have been broken?
TDK 113G1 used and this is compatible with this? http://uk.farnell.com/murata-power-solutions/76602-1c/transformer-pulse-1-1-1/dp/1087810

Thanks!
Krisz



« Last Edit: June 10, 2018, 12:49:13 am by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #99 on: June 10, 2018, 02:08:15 am »
T2 may have broken down.
T1 - I do not think it burned out
Check the keys and the comporator!
T2 is installed at the output. K through it could discharge the capacitor.
Check Q4.!
« Last Edit: June 10, 2018, 02:15:23 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #100 on: June 10, 2018, 04:03:49 am »
Ok, I solder out.
1040 hFE with a multimeter. I think it is ok.
« Last Edit: June 10, 2018, 05:04:37 am by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #101 on: June 10, 2018, 05:29:04 am »
You can check the transformer in any circuit or generator
if there is a low output impedance.
U5-?
If the transformers are identical, change between them.
« Last Edit: June 10, 2018, 05:35:43 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #102 on: June 10, 2018, 05:44:49 am »
Checking
I ordered U5 to U10 new ICs. I don't have the place to check the U5 when the card is inserted.
« Last Edit: June 10, 2018, 06:48:47 am by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #103 on: June 10, 2018, 07:46:35 am »
Checking
I ordered U5 to U10 new ICs. I don't have the place to check the U5 when the card is inserted.

U5 replacement with a new one. So faster.
Just install it on the panel.
The transformer must be removed and connected to the generator.
Emulate the signal is real!
The secondary winding of the load and see the amplitude level and waveform.
If it's bad you'll notice.

I installed the Sockets!



Here is a weak spot. Therefore it can happen again.

3g57
« Last Edit: June 10, 2018, 08:01:44 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #104 on: June 10, 2018, 08:32:05 am »
Hi,

Quick I soldered out the A3T1.
Source: 1Vrms 1kHz sin wave

Here are the results:

N2



N3



It looks good?
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #105 on: June 10, 2018, 08:40:31 am »
not happy.
what signal at the transformer input?

Try the second one. for comparison.
Do not confuse the transformers.
« Last Edit: June 10, 2018, 08:46:30 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #106 on: June 10, 2018, 08:45:05 am »
Source: 1Vrms 1kHz sin wave

I try the second now.
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #107 on: June 10, 2018, 09:09:52 am »
Here is the A3 T2.
Source same: 1Vrms 1 kHz sin wave

N2



N3



Both transformers output similar. Both good or both bad?  :)
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #108 on: June 10, 2018, 09:10:55 am »
You can assume that he is normal.
Two could not burn.
In this way, check the output transformers. Only necessary
load them.
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #109 on: June 10, 2018, 09:14:30 am »
Good news that they are good.  Do you think as output transformer A3 T3, T4, T5?
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #110 on: June 10, 2018, 09:18:58 am »
Good news that they are good.  Do you think as output transformer A3 T3, T4, T5?

It is necessary to check at least this way.
With a good generator and Extender boards, everything was much easier. Disconnect the input. At the input of the cascades, give the necessary signal and follow the path of the oscillograph with the oscillograph. Watch where he is lost.

p.s.  Krisz! soon morning. I'm going to go to bed.

Send me screenshots!
« Last Edit: June 10, 2018, 09:27:03 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #111 on: June 10, 2018, 09:27:50 am »
Now I know what the extender board is good for. :) I have a Philips signal, it can everything.
Disconnect the signal, do you mean A3 J1?



 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #112 on: June 10, 2018, 09:31:48 am »
Disconnect the signal, do you mean A3 J1?

Transformer input T1.
Do not rush. Till tomorrow!
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #113 on: June 10, 2018, 09:43:24 am »
Ok, tomorrow continue. Good night! :-)
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #114 on: June 11, 2018, 04:10:54 am »
Hi,

I checked the BNC sockets, on the front side.It is missed from your the checklist what you wrote. All wires tested for shorts to chassis. No shorts between the pairs too.
Lc - Blue wire - OK
Lp - Red wire -  OK
Hc - Yellow - OK
Hp - White - OK

Krisz
« Last Edit: June 11, 2018, 04:59:26 am by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #115 on: June 11, 2018, 08:17:50 pm »
Krisz! Hi!
You have another option.
Take out the module and on the table give him the necessary + 12V / -12V.
On T1, give the necessary signal. Next, with an oscillograph, look at it.
 

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Re: HP 4274A LCR Meter - mini teardown
« Reply #116 on: June 12, 2018, 04:56:48 am »
Hi,

I found an interesting article about, how to test the pulse transformers. https://scienceprog.com/testing-pulse-transformer-with-an-oscilloscope/
I checked both transformers secondary n2, n3 and all right.  You see in the scope pic.
The Bias Controller arrived.
I bought U5 - U 10 ICs. I replace them, it is maybe slowly because I hate desoldering ICs from PCB. :)







« Last Edit: June 12, 2018, 05:08:03 am by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #117 on: June 12, 2018, 06:59:20 am »
Signal levels are performed by U5.
This is the table.
Gives commands from the DSA- TRD DECODER.
You have a weak signal level.
Here's your task.

When you set the potentiometer signal to the maximum you do not have an error. Do I understand correctly?
It was on the video.
If you have cascaded amplifiers in good order, then you need to search for the reason with the teams!
« Last Edit: June 12, 2018, 08:34:52 am by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #118 on: June 12, 2018, 07:29:31 am »
Hi,

Today I bought U5 IC it is called LM339N and sockets. It is a good replacement?  I replace first time the U5 now. I don't have any space for the measure when the card is inserted :( May I solder on the pins of the IC little wires, but it is very homemade version... what do you think?
I tested the Bias controller, looks like it is working! :)




 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #119 on: June 12, 2018, 07:42:02 am »
May I solder on the pins of the IC little wires, but it is very homemade version... what do you think?

I did not understand the question.
What to solder?
« Last Edit: June 12, 2018, 07:43:59 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #120 on: June 12, 2018, 07:46:25 am »
If I insert the card, I don't have any space for measuring. But if I solder short wires on the U5 339IC pins, I can measure the correct DC levels? I know it is very amateur, but I don't have extension cards yet.
The LM339N good for U5?
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #121 on: June 12, 2018, 07:51:19 am »
You first plug in and turn it on. Will there be an error?
To solder to it is not a good option!
If you are sure that there are no problems with amplifiers and after the replacement of U5
there is an error then there is no command on U5.
The signal with U5 can be checked in the key bases Q ...... Q
They are installed at the top and they can be reached.

« Last Edit: June 12, 2018, 08:46:07 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #122 on: June 12, 2018, 09:04:40 am »
I am replaced the U5 but nothing changed. ERR 4 still flashing. Do you think Q2 to Q5?

Krisz
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #123 on: June 12, 2018, 09:11:05 am »
Maybe. It is necessary to change.
It is desirable to measure the levels c U5.
U5 adjusts the signal level at the output U2.
R14 at the output U1.
How do I remember the output of U1 was close to normal?
« Last Edit: June 12, 2018, 09:17:30 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #124 on: June 12, 2018, 09:17:21 am »
Ok, I try to measure the transistors. :) What level need there?
I not measured yet the U1 output voltages.
« Last Edit: June 12, 2018, 09:23:50 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #125 on: June 12, 2018, 09:24:01 am »
Ok, I try to measure the transistors. :) What level need there?

You have a table.
In bases Q ..... Q on the command table with logical levels.

 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #126 on: June 12, 2018, 09:29:13 am »
I not measured yet the U1 output voltages.

You wrote me * A3 TP2 8,4Vpp - OK *
I rely on it!

« Last Edit: June 12, 2018, 09:40:01 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #127 on: June 13, 2018, 01:29:36 am »
Yes, it is. I confirmed :) Sorry I just mixed up.
I measuring the Q2-3-4. In progress.
« Last Edit: June 13, 2018, 03:06:47 am by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #128 on: June 13, 2018, 04:09:27 am »
I measuring the Q2-3-4. In progress.

Hi!
You need to go through the check on
cascades and set the required signal levels.
This is just the top of the A3.
Similarly, it is necessary to pass the bottom of A3.
Because they work synchronously.
I'm showing you on the screen.



Unfortunately I do not have a good file.
This is not all legible.

3g57
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #129 on: June 14, 2018, 06:07:50 am »
Hi,

I measured the Q2, Q3, Q4

Values:

Multi x0,01 x0,1  x1   x5
Q2 out after R24    -10,98 -10,98 -10,98 +6,4
Q3 out after R25    +6,4 -10,98 -10,98 -10,98
Q4 out after R26    -10,98 +6,4 -10,98 -10,98

I measured the DC voltage on A3 L2 and there is +11,2V

I measured on U5 14 pin the DClevel (for more pin need a little more space for checking, but I don't have)

x0,01 - -10,98
x01 - -10,98
x1 - -10,98
x5 - -10,98

In x1 position need + voltage or not?

Krisz
« Last Edit: June 14, 2018, 07:10:06 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #130 on: June 14, 2018, 09:17:50 pm »
Hi! Krisz.
I watched.
This module has two common buses.
1- digital
2- analog
When you take measurements take it into account !!!
You should first of all make measurements of the signal levels at the input U7 / U6 / U5.
This way you can check the low and high levels of signals and compare with the table.
U7 / U6 / U5 create a signal level for the analog part
and send it to the keys Q2 / Q3 / Q4, Q10 / Q11 / Q12 / Q13 / Q14.
A high and a low level is better measured by an oscillograph. In DC open mode.!!!
Make a table for yourself.!
On your question:
Extender boards buy for yourself convenient.
If you want, you can wait for me next week, I can send
you need a file to make it.
This mine, but it is not high. There will be another, adapted for HP4275A




Check D-GND! So on the board?






________________________________








3g57
« Last Edit: June 14, 2018, 10:23:09 pm by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #131 on: June 15, 2018, 03:00:28 am »
Hi,
Just a quick question. For the sake of clarity I ask it:
A-GND - A11 11-13L
D-GND - A11 7R

What are on A11 4R? (Bias Monitor RTN) It is same as A-GND?

I just checked the A11 board again and A-GND and D-GND and 4R are on common potential and connected to chassis. (All boards inserted)

Krisz
« Last Edit: June 15, 2018, 03:46:55 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #132 on: June 15, 2018, 04:07:59 am »
1- The analog common bus typically supplies
operational amplifiers, etc.
2- The digital common bus usually supplies logic elements, CPU, etc.
They can communicate under certain conditions. As a rule, this is done
through the denouement.
At this device I watched 4 tires !!!!

You can find the answer to the second question in this diagram.
I painted her color.



Here the screening braid has its meaning.
It additionally performs an active role with a certain
connection. Learn. It is important.

Pay attention!!!! On the numbers in the triangle!
This is an example with the HP4275A



« Last Edit: June 15, 2018, 04:30:18 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #133 on: June 15, 2018, 05:20:31 am »
Hi,

Here are the quick results:

Multi    x0,01     x0,1     x1    x5
U5-4     L            H        H     H   (U5 replaced)
U6-4     H            H        H     H
U7-4     H            H       H      H

High is +4V DC
GND A11-7R
It is good?

More results in progress.
I don't have numbers in the triangles on the schematic.

D-GND between A11-R7 and U8-10, U9-10, U10-10 are OK.

Krisz
« Last Edit: June 15, 2018, 05:26:07 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #134 on: June 15, 2018, 05:57:03 am »
Hi,

Here are the quick results:

Multi    x0,01     x0,1     x1    x5
U5-4     L            H        H     H   (U5 replaced)
U6-4     H            H        H     H
U7-4     H            H       H      H

Krisz.
What is U5-4, U6-4, U7-4 ????
« Last Edit: June 15, 2018, 06:28:17 am by 3g57 »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #135 on: June 15, 2018, 06:10:43 am »
You need a level only U5 !!!
So far only at her entrance.
See the table.
Signal to U5 input
TLHT   - pin10
TLS#1 - pin8
TLM     - pin6
TLL      - pin4
Make a table for yourself when multiplexer is running.
« Last Edit: June 15, 2018, 07:16:40 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #136 on: June 15, 2018, 06:32:34 am »
Here is the table:

Multi    x0,01     x0,1     x1    x5
U5-4     L            H        H     H
U5-6     L            L        L     L
U5-8     H            H       H      H
U5-10   H            H        H     H

U5-10 is U5-pin10
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #137 on: June 15, 2018, 06:50:28 am »
Check. I'm not wrong.



This is the table.



Check now the levels at the output of U5, only relative to the analog common bus of 12L.
Make a table.!

p.s. I rely on your measurements.
If they are right, then you have a problem up to U5!
ATT does not work correctly. Therefore, further error.
It should also be taken into account that U5 controls the lower part of the circuit A3.
This will also be a mistake!


3G57
« Last Edit: June 15, 2018, 08:28:44 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #138 on: June 15, 2018, 07:23:37 am »
Hi,

I measured again with same as your table.

Multi    pin10     pin8     pin6    pin4
x5        L            H        H     H
x1        H            H        H     H
x0,1     H            H       L      H
x0,01   H            H        H     L

But it is normal that the Hcur signal on the Bias monitor socket?

Krisz








 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #139 on: June 15, 2018, 07:29:30 am »
Hi,

I measured again with same as your table.

Multi    pin10     pin8     pin6    pin4
x5        L            H        H     H
x1        H            H        H     H
x0,1     H            H       L      H
x0,01   H            H        H     L


This does not correspond to the norm in the table!
So it does not work properly!
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #140 on: June 15, 2018, 07:32:41 am »
But it is normal that the Hcur signal on the Bias monitor socket?

Understand the scheme!
I did not penetrate.

________________

Yes. Through the resistor R43

« Last Edit: June 15, 2018, 07:44:43 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #141 on: June 15, 2018, 07:43:08 am »
Check the levels on U5 pin1, pin2, pin13,14?

I just asked the signal level at Bias monitor, never check this before.

But don't understand how not work properly the U5 when on Hcur socket the signal levels are correct.
 
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #142 on: June 15, 2018, 07:48:24 am »
Check the levels on U5 pin1, pin2, pin13,14?
I just asked the signal level at Bias monitor, never check this before.

Compare the table and your measurements.

You have a problem up to U5 !!


At the output of U5, you have not measured.

p.s.  Yet. Read in the manual. Measurements must be made with the connected
TEST FIX. 16047 or without it ??  It is important!
« Last Edit: June 15, 2018, 08:28:14 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #143 on: June 15, 2018, 08:30:26 am »
Hi,

I check the U8-9 levels?
I attached the fixture.

 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #144 on: June 15, 2018, 08:36:41 am »

I attached the fixture.

Once again, check the U5 levels after installing the TEST FIX. 16047
 Make a table.!
With U8 / U9 later.
« Last Edit: June 15, 2018, 08:39:20 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #145 on: June 15, 2018, 08:39:10 am »
Ok, just a moment.
But the fixture, not original 16047, it is B+K Model TL89F1.
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #146 on: June 15, 2018, 08:40:29 am »
Let it be for now. :-\
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #147 on: June 15, 2018, 09:08:28 am »
I repeated the U5 measure, and nothing changed.
The B+K fixture working with 4274A. Here is the article:
http://k6jca.blogspot.com/2017/11/replace-hp-16047a-test-fixture-with-bk.html
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #148 on: June 15, 2018, 09:16:39 am »
Krisz!
Hence it is necessary to replace U8, U9, U10.
Install the sockets for them. It will be faster than checking !!!
You can not do this.
p.s. You can try, maybe they are good?
Perhaps the problem is up to them.

3g57
« Last Edit: June 15, 2018, 09:23:38 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #149 on: June 15, 2018, 09:27:35 am »
 I hope! Tomorrow the first thing will be that I replaced them! :-) Thanks your help! 
Krisz
How test these ICs?
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #150 on: June 15, 2018, 09:31:57 am »
How test these ICs?

Replace! They are not expensive.
Install it in the sockets.
Replacement only for the same.
« Last Edit: June 15, 2018, 09:34:26 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #151 on: June 15, 2018, 09:34:39 am »
 ok, I bought sockets and ICs some days ago.  I can replace them quickly.
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #152 on: June 15, 2018, 09:38:24 am »
Krisz! I did not study the manual on the HP4274A.
With HP4275A they have a difference! ^-^
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #153 on: June 15, 2018, 09:55:54 am »
I waiting the morning! :-) If I replaced and the open and short calibration succes we are ok :-)
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #154 on: June 16, 2018, 05:12:26 am »
Hi,

I replaced the U8-9-10 IC-s but, ERR4 still flashing.

Please check the service manual 5.19 section. Maybe it is important.



Krisz
« Last Edit: June 16, 2018, 06:45:06 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #155 on: June 16, 2018, 05:43:09 am »
Hi. measure logical levels now.
Until you restore them, the car will not go.
The analog part here does not take part.




Your signal levels do not correspond to passport standards. The multiplexer controls these signals. It is necessary to bring this back to normal.
« Last Edit: June 16, 2018, 06:01:56 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #156 on: June 16, 2018, 08:04:34 am »
How can I restore when I measured the logical levels?
For this measure on A7 need the extension, because of the ICs at the bottom side of A7 board.
« Last Edit: June 16, 2018, 08:31:48 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #157 on: June 16, 2018, 09:03:52 am »
A7 do not touch yet.
You need to measure the levels again at the input of U5.
Make again the table and compare it with the previous one.
Further in the chain on A3, you did not check the last node.
This is LATCH! It can inhibit the passage of the signal to U8 / U9 / U10.
To do this, it was installed. With him you need to understand.









3g57
« Last Edit: June 16, 2018, 09:29:19 am by 3g57 »
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #158 on: June 16, 2018, 11:57:21 am »
Hi,

I have been following this thread. Are you sure that your HP4274A is broken?

Let me show you what happens with a perfectly healthy 4274A.

If I press the ZERO open button with no fixture connected to the HP4274A Err 1 is displayed:



If I connect an HP16047A fixture to the HP4274A and press ZERO open, the HP4274A displays CAL until the ZERO open is complete:



If I connect all the shield of the BNC connectors together and connect Lcur to Lpot and Hcur to Hpot and I press the ZERO cal the test is performed the same way as with the 16047A fixture:




Here is a close up of the wires:





The BK Precision Test fixture may not be wired the same way as the HP fixture. I would check it.


Regards,

Jay_Diddy_B

« Last Edit: June 16, 2018, 12:04:36 pm by Jay_Diddy_B »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #159 on: June 16, 2018, 06:30:15 pm »
Hi,

I tested the zero calibration with simple wires, but first time CAL, ERR1, and ERR4 flashing.
In zero offset adjustment need to set the multiplier in x5 position? the user manual says yes.

I found an article that BK fixture working with 4274A.
http://k6jca.blogspot.com/2017/11/replace-hp-16047a-test-fixture-with-bk.html
I think need to work the fixture with 4274A.

A little history: When arrived the 4274A first time worked, but I don't had a fixture. I made a handmade fixture using alligator clips, and it is worked. I could measure R C L parts. Then I left from my workshop, but the 4274A stayed power on. 2 hours later I came back, and ERR4 flashing on display. I don't know what happened, nobody touched the 4274A.

Can you send me a similar photo from 4274A? Need compare with yours. You see this if Push the SELF Test and D button.



Thanks!
Regards,
Krisz
« Last Edit: June 16, 2018, 07:14:44 pm by MateKrisz »
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #160 on: June 16, 2018, 08:23:28 pm »
Krisz and the group,

Here is the self test section from the manual.

This is a summary:




Regards,

Jay_Diddy_B
 

Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #161 on: June 16, 2018, 08:26:27 pm »
Hi,

Here are the results from my 4274A with the 16047A installed:



Regards,
Jay_Diddy_B
 
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Offline Jay_Diddy_B

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Re: HP 4274A LCR Meter - mini teardown
« Reply #162 on: June 16, 2018, 08:28:13 pm »
Hi,

The rest of the self-test results:


Regards,

Jay_Diddy_B
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #163 on: June 16, 2018, 09:06:33 pm »
Hi! Krisz.



The only digital bus that goes
on A3 this is STROBE CLOK DECODER.
She manages DSA-2. Even when checking (see FIGURE 8-31), I send the instruction to the address U216 (MC U20 74LS74N).
Here, a signal is generated for the digital part A3.
This creates the necessary signals for U8, U9, U10. LATCH.
A task:
It is necessary to achieve the normal operation of these microcircuits(MULTIPLEXER).



3g57
« Last Edit: June 17, 2018, 12:27:42 am by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #164 on: June 17, 2018, 02:58:11 am »
Hi all,

Quick I made a video about the self-test:


At A3 TP3 I found 1Vrms. But this value depends on FREQ and Multiplier settings.
Flowchart wants there 3,3Vrms. How could be 3,3 Vrms if depend on multiplier?
Multiplier x1, FREQ 1 kHz:



I checked the A7 board test points:


A7TP10 - Hi-Lo switching
A7TP11 - Hi (+4V)
A7TP12 - Hi-Lo switching
A7TP13 - Hi
A7TP7 - Hi (+5V)
A7TP18 - Hi
A7TP5 - Lo

Krisz

PS.: May I replace the A7 U20?

Thanks!
Krisz
« Last Edit: June 18, 2018, 07:09:08 am by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #165 on: June 18, 2018, 07:03:43 pm »
Krisz! Hi.
You can replace U20. Install it on the socket.
Look at the situation.
You make measurements and do not specify under what regime it was done! It is very important. You give the results of measurements. How can I guess? The digital part does not work correctly.
Look at your last measurements! Tp11-A7. pin # 34 * RESET *.
You have a high level on it. It is activated.
The * ENABLE * Tp10-A7 pin # 25 is followed by continuous
switching (A7TP10 - Hi-Lo switching).
Why is this happening and under what conditions?
It is necessary to measure the reference frequencies of quartz
resonators. Pretty sure. The instruction writes about an error up to 20ppm.
There are three quartz resonators.
* RESET * can occur due to the breakdown of the reference (inaccuracy) frequency.
p.s. I asked the mail about the battery. There was no answer.
You can not do without an expansion board.
3g57
« Last Edit: June 18, 2018, 07:09:23 pm by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #166 on: June 19, 2018, 06:18:24 am »
Hi,

Sorry, I just now see your messages. I did not get an e-mail about the new post and the PM message. I ordered the U20 IC, it is will arrive circa Friday.
I always made the measurements with the default settings, except if flowchart or you don't want other settings.
On my 4274A not installed the memory backup option. If exist other battery where can I find it?
I think I order 2 extension card from the original manufacturer: http://www.douglas.com/index.php/6-de-6.html with sockets. I ask them, what is the real shipping cost because the calculator said 100-200 USD. It is too expensive for these little cards.

Krisz
« Last Edit: June 19, 2018, 07:11:09 am by MateKrisz »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #167 on: June 20, 2018, 02:58:10 am »
Hi,

It is my A9 board w/o battery. I measure again on the A7 board?

Krisz


 

Offline precaud

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Re: HP 4274A LCR Meter - mini teardown
« Reply #168 on: June 20, 2018, 01:40:02 pm »
As I discovered when repairing my 4275A, you are better off leaving the battery out while troubleshooting. Also remove the GPIB board (and DC bias bpard if it has one) until you find your problem(s).
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #169 on: June 20, 2018, 07:22:06 pm »
Good idea! Thanks! :)
 

Offline precaud

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Re: HP 4274A LCR Meter - mini teardown
« Reply #170 on: June 20, 2018, 10:36:02 pm »
Also remove the socketed EPROM labeled "19", that is for the GPIB board.
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #171 on: June 21, 2018, 05:43:56 am »
OK! :)
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #172 on: June 21, 2018, 05:57:53 am »
Hi 3g57,

The U20 IC has arrived. I replace them. Maybe it was broken.

Update: Replaced but nothing changed. Still ERR4 flashing

Krisz
« Last Edit: June 21, 2018, 08:30:17 am by MateKrisz »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #173 on: June 26, 2018, 04:50:23 am »
Hi,

The brand new original Sony C1636 transistors have arrived. I tested them, and replace on A3 board.

Krisz
 


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