Electronics > Repair
Agilent 34401A Bubble on PCB ... can it be saved ? (SOLVED)
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The_Spectrum.A_idiot:
the rest of the ranges measure same as before.

okay.
The_Spectrum.A_idiot:

--- Quote from: Dr. Frank on September 24, 2024, 03:45:52 pm ---what about 1M and 100k ranges?

Next step: Please remove Q203 and measure these 3 currents from pin 2 of Q202 to AGND / INPUT LO.

Frank

--- End quote ---

Q203 removed and cleaned everything flux coated

results :'(
pin 2 of Q202 to INPUT LO
000. ohm range -997.6 μA
0.1k range - 997.6μA
00.1k range -99.38μA
000.1k range -9.89μA
0.1M range -4.92μΑ
00,1M range - 0.35μΑ **
000,1Μ range -0,34μΑ **

Thank you in advance
Dr. Frank:
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
The_Spectrum.A_idiot:
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
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 ---

I got this from mouser.
https://eu.mouser.com/ProductDetail/584-AD706JRZ

No ebay or unknown source components.
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