Hi, I'm quite aware that calibrating a 6.5 digits dmm with another 6.5digits dmm is quite meaningless.
And it’s is good to make it clear before the metrology experts start shouting at me.
Last time I asked for a quote to a cal lab, when I was back in Norway, they asked around 500€ to do a keithley 2000, something much easier to adjust that the 3456A, that would be outside my budget…
The reasoning for the self cal is that I should anyway get the instrument in a “usable” state to make sure it does work properly before investing in a proper adjustment (if ever that occasion comes up).
At the moment the 3456A is not a functioning instrument, the DCV cal seems ok as it agrees very well with the keithley 2000, but ACV and resistance are a bit wonky and anyway when I got the unit the seals were broken so, there is not much to preserve.
As per calibration sources, wouldn’t the 3245A be a good source (up to 10V)? It is a lm399 based instrument, short therm stability should be quite good.
Anyway, if Vgkid is correct I might not able to repair this unit at all, still cannot find references on the service manual on how to replace U200, which is odd given that many troubleshooting procedures end in “replace U200”