Re: 2445A calibration


On Wed, Oct 17, 2018 at 02:08 PM, Siggi wrote:

Awesome, congratulations!
This has been one of the more epic repair threads I've seen here recently,
it was fun to see some of the firmware disassembled. Super-fun to see the
firmware matched my calculation to within 2/4096.
Did you measure the +1.36/-1.24V references after your repair (and DAC
re-calibration)? I'd be most interested to know what the final values of
those reference voltages were against the centered +1.25/-1.24 DLY REF
Apparently 0.5% from the calculated value is too far out, but the -1.25V
value on the schematics is still 0.25% out - the truth is out there!
Thank you Siggi. I had no time to re-measure the test points, I'll do it today. But now DAC is centered (pin 13 J119) between -1.250V and 1.250V, which is quite amazing. I hope that the results will converge with the LTSpice simulated values. After changing the op-amp I have noticed that the OPAMP instead producing -8.1V started pulling the -1.25V line more -8.8V. And everything worked after that.

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