Author Topic: HP 4274A LCR Meter - mini teardown  (Read 28339 times)

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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #75 on: June 07, 2018, 07:34:30 pm »
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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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #76 on: June 07, 2018, 08:15:29 pm »
 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 07, 2018, 08:29:29 pm by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #77 on: June 07, 2018, 08:23:25 pm »
Ok, thanks! :)
The fixture will arrive tomorrow! :)
« Last Edit: June 07, 2018, 08:52:35 pm by MateKrisz »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #78 on: June 08, 2018, 11:27:49 am »
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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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #79 on: June 08, 2018, 12:44:42 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!

https://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 08, 2018, 02:03:01 pm by 3g57 »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #80 on: June 08, 2018, 01:36:40 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, 04:39:32 am by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #81 on: June 08, 2018, 05:45:38 pm »
Hi,

Thank you! I now measure the suggested areas.
I come back later with values.
Krisz
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #82 on: June 08, 2018, 05:50:28 pm »
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 08, 2018, 06:03:23 pm »
On A3 board?
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #84 on: June 08, 2018, 06:05:23 pm »
« Last Edit: June 08, 2018, 06:07:48 pm by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #85 on: June 08, 2018, 06:51:28 pm »
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 08, 2018, 06:54:47 pm by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #86 on: June 08, 2018, 07:03:12 pm »
You wrote to me that with the oscillator is normal! :-\
Now go from the oscillator! |O
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #87 on: June 08, 2018, 07:04:53 pm »
Yes, it was normal and worked fine, but now I just checked and you see that what measured. :/
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #88 on: June 08, 2018, 07:07:04 pm »
Yes, it was normal and worked fine, but now I just checked and you see that what measured. :/

Do not understand.
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #89 on: June 08, 2018, 07:15:08 pm »
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.
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #90 on: June 08, 2018, 07:26:15 pm »
Open the manual and see FIGURE 8-31.
Follow the path.
DSA2 is a TRD DECODER
Bottom left.
« Last Edit: June 08, 2018, 07:30:29 pm by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #91 on: June 08, 2018, 07:36:28 pm »
OK :)
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #92 on: June 08, 2018, 08:22:10 pm »
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 08, 2018, 08:51:42 pm »
 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 08, 2018, 09:08:38 pm by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #94 on: June 08, 2018, 09:02:18 pm »
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 08, 2018, 09:09:42 pm by MateKrisz »
 

Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #95 on: June 08, 2018, 09:20:17 pm »
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 08, 2018, 09:26:48 pm by 3g57 »
 

Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #96 on: June 08, 2018, 09:27:10 pm »
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, 12:06:51 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, 01:31:48 pm by 3g57 »
 
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Offline MateKrisz

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Re: HP 4274A LCR Meter - mini teardown
« Reply #98 on: June 09, 2018, 02:43:28 pm »
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 09, 2018, 02:49:13 pm by MateKrisz »
 
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Offline 3g57

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Re: HP 4274A LCR Meter - mini teardown
« Reply #99 on: June 09, 2018, 04:08:15 pm »
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 09, 2018, 04:15:23 pm by 3g57 »
 


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