Author Topic: HP 4274A LCR Meter - mini teardown  (Read 25648 times)

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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...)
 

Offline 3g57

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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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Offline MateKrisz

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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
 

Online BravoV

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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 »
 

Offline precaud

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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.
 

Offline 3g57

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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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Offline MateKrisz

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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
 

Offline 3g57

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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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Offline MateKrisz

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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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Offline 3g57

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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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