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 13, 2024, 09:32:48 am ---Hello Unknown,
it's a pity that some people don't even reveal their first name. I don't like to cite SUCH alias names, in first place  :palm:

From a closeup of the damaged PCB, I strongly assume, that somebody tried to repair the instrument, using a hot air gun around U110, or the Ohm protection transistors Q203 - Q210, either to replace or re-insert them.
That guy used too much heat, also too long, and did not cover the other components, so creating this PCB delamination.
It's not clearly visible, but all components inside  the area of delamination might have been damaged by the heat, at least all the solder joints are under suspect.
Please make a macro photo exactly vertical above this area, so that every component and solder joint is sharp, and better illuminated, maybe from different sides.

The transistors  have been soldered very badly, and I see solder balls. The transistors might be defective, or there might be a short to GND as well , via Q211 which should be tested in situ.
If you select 4W Ohm, do you measure the appropriate test currents out of + Input and - Input for the different (manually selected) ranges?

You have to de-solder these transistors anyhow, so you can test them individually, later on.

W/o the transistors back in place, you might then solder a short from Q202 to CR202 temporarily, to make further tests on the Ohm mode.
Descriptions how to do that, has been written down elsewhere .. I guess you found that thread already, as you copied the OHM schematic here.

I guess, that U110, that is used for current mode protection, has been replaced, but that mode should work properly, and has nothing to do with your OHM problem. Anyhow, many of the solder joints look very bad. U304 also looks bad.

We will definitely continue analysis, when you have presented further results.

Frank
 

--- End quote ---

Dear Dr. Frank ,

Regarding the screen name is a long story but it showed my superficial and lack of deep knowledge of the subject.

I took my time with the pictures and its WAY WORSE than I ever imagined.

please have a look and we will iron out the details later.


The_Spectrum.A_idiot:
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The_Spectrum.A_idiot:
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The_Spectrum.A_idiot:
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The_Spectrum.A_idiot:
last batch I promise
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