Electronics > Repair
Agilent 34401A Bubble on PCB ... can it be saved ? (SOLVED)
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The_Spectrum.A_idiot:

--- Quote from: Dr. Frank on September 24, 2024, 04:20:32 pm ---Ok, please re-insert CR202 and Q203. You might then test these currents on the outside (Input Lo / Hi) again.

Have you tested the old components, Q203-Q210, Q211, Q202 and CR202 if and how they had been damaged?

If these parts are all damaged there had been a very high overvoltage event, which could have affected U201-B, but also C210 and U101-E.

So my next guess would be to remove or replace C210, that's a 0805 ceramic capacitor .. I don't know if it's a special type for low leakage currents..
It's a COG / NP0, which usually has better insulation than X7R. You might check this components outside for leakage, when applying 20V in series.

Have you got a genuine, new AD706?

Frank

--- End quote ---

regarding the C210
this is what the service manual said about it :

C210 0160-5954 4 Capacitor-Fxd 220 pF ±5% 50 V 04222 08051A221JAT A

This is the closest I can find

https://eu.mouser.com/ProductDetail/KYOCERA-AVX/08051A221JAT2A?qs=j3sIhLrTlovso9JF71DsEg%3D%3D
Dr. Frank:

--- Quote from: The_Spectrum.A_idiot on September 24, 2024, 04:41:01 pm ---Q202 I was in between what component to select

I was between :

https://eu.mouser.com/ProductDetail/512-MMBFJ176 (this one is installed)

and

https://eu.mouser.com/ProductDetail/106-SMP5461

I will reinstall the rest and order the capacitor

If U101 is broken I should assume that this is the end of this journey right ?

Thank you in advance

--- End quote ---


That JFET should Q211 should be fine, but I meant U201, if you bought a genuine AD706, or have you picked another type?

Please first remove C210, maybe the OpAmp will not oscillate, and you can test the currents, before ordering.

If U101 is damaged, you might be able to re-calibrate the Ohm ranges, which would then compensate for the additional leakage currents.

I expect that up to 1MOhm range, it will still work ok, 10M and higher might be unstable (over temperature, time), and maybe you will not be able to calibrate these upper ranges properly.
DCV seems to be ok, but you will always get these Test Errors 612, 618, because the 500nA current is outside of tolerance.     

If you can live w/o the higher Ohm ranges, your 34401A might be still quite usable, but it needs a full check of all ranges and modes.

Frank
Dr. Frank:

--- Quote from: The_Spectrum.A_idiot on September 24, 2024, 04:45:41 pm ---
--- Quote from: Dr. Frank on September 24, 2024, 04:20:32 pm ---Ok, please re-insert CR202 and Q203. You might then test these currents on the outside (Input Lo / Hi) again.

Have you tested the old components, Q203-Q210, Q211, Q202 and CR202 if and how they had been damaged?

If these parts are all damaged there had been a very high overvoltage event, which could have affected U201-B, but also C210 and U101-E.

So my next guess would be to remove or replace C210, that's a 0805 ceramic capacitor .. I don't know if it's a special type for low leakage currents..
It's a COG / NP0, which usually has better insulation than X7R. You might check this components outside for leakage, when applying 20V in series.

Have you got a genuine, new AD706?

Frank

--- End quote ---

regarding the C210
this is what the service manual said about it :

C210 0160-5954 4 Capacitor-Fxd 220 pF ±5% 50 V 04222 08051A221JAT A

This is the closest I can find

https://eu.mouser.com/ProductDetail/KYOCERA-AVX/08051A221JAT2A?qs=j3sIhLrTlovso9JF71DsEg%3D%3D

--- End quote ---

That's perfect. But please, check the OpAmp and w/o C210 , before ordering.
Maybe it's the wrong OpAmp (low bias type!) or you test another sample first.
The_Spectrum.A_idiot:

--- Quote from: Dr. Frank on September 24, 2024, 04:53:21 pm ---
--- Quote from: The_Spectrum.A_idiot on September 24, 2024, 04:45:41 pm ---
--- Quote from: Dr. Frank on September 24, 2024, 04:20:32 pm ---Ok, please re-insert CR202 and Q203. You might then test these currents on the outside (Input Lo / Hi) again.

Have you tested the old components, Q203-Q210, Q211, Q202 and CR202 if and how they had been damaged?

If these parts are all damaged there had been a very high overvoltage event, which could have affected U201-B, but also C210 and U101-E.

So my next guess would be to remove or replace C210, that's a 0805 ceramic capacitor .. I don't know if it's a special type for low leakage currents..
It's a COG / NP0, which usually has better insulation than X7R. You might check this components outside for leakage, when applying 20V in series.

Have you got a genuine, new AD706?

Frank

--- End quote ---

regarding the C210
this is what the service manual said about it :

C210 0160-5954 4 Capacitor-Fxd 220 pF ±5% 50 V 04222 08051A221JAT A

This is the closest I can find

https://eu.mouser.com/ProductDetail/KYOCERA-AVX/08051A221JAT2A?qs=j3sIhLrTlovso9JF71DsEg%3D%3D

--- End quote ---

That's perfect. But please, check the OpAmp and w/o C210 , before ordering.
Maybe it's the wrong OpAmp (low bias type!) or you test another sample first.

--- End quote ---

https://eu.mouser.com/ProductDetail/584-AD706JRZ

this is the OP-AMP Ι could find.

Wιthout the C210 current when up to 0.44μΑ

Waiting on your response.
Dr. Frank:
and the other currents, 5µA and 10µA?

Does it now pass the test?

That means, DIP 8 is obsolete, and you have used an SOIC / DIP adapter? Or was it an SO package initially? I don't remember..
This type is correct, anyhow
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