Signal Recovery 5113 pre-amp calibration procedures - Any ideas or experience?

[CorporateReference]

We had to replace the 2 front end FETs on our SR 5113, however after doing so the overload indicators are coming on at certain gains.  From our experience with the Stanford Research SR560, several trimmers need to be adjusted after such a procedure.  Signal Recovery/Ametek Support is non-responsive or unknowledgeable thus far and the manuals do not mention calibration proceedures.  Does anyone here have any experience?

The SR560 lists such a procedure here: https://www.thinksrs.com/downloads/pdfs/other%20stuff/SR560_offset.pdf

The architecture is very similar so I could infer what to do, but if anyone has any "insider" info that would be greatly appreciated.

[_Wim_]

The architecture is very similar so I could infer what to do, but if anyone has any "insider" info that would be greatly appreciated.

Not have come across this, but would be great to have this info indeed

Signal Recovery/Ametek Support is non-responsive or unknowledgeable thus far...

I also did not have any luck getting support when repairing my 5113. However, when I asked for support repairing a few lock-in amplifiers, they did offer excellent support  , so it really does depend on who handles the request within the company.

I can make some measurements on my 5113 unit if required, so you have a reference. Just ask what you need measured.

[_Wim_]

Attached a picture of the much simpler 5186 that uses the same topology (npd5564 + INA103 + AD opamps).

This board has the adjustment pots labeled:
- R41: drain I  (1K)
- R28: DC Off (1K)
- R11: O/P Off (10K)

I expect the 5113 to have a similar config.

[RaymondMack]

I'd also like to know the adjustment procedure. It's unfortunate that calibration documentation has been removed from modern manuals. I guess someone thought they could squeeze more money out of their products if they had to be sent back for adjustment. Even the Chinese are following suite with this mentality (Rigol in particular).

I suspect we might have to just draw out the circuit and make educated guesses on how to adjust these amplifiers. I had to do this with my Clarke Hess 2330 sampling power meter which was pretty straight forward. That said, the official cal procedure stores the zero offsets of the ADCs in EEPROM which I've yet to figure out. So I haven't been able to perform a complete cal adjustment, much to my chagrin.