[volt-nuts] HP-3455A calibration

[Jeremy Nichols]

My new-to-me 3455A DVM (s/n 1622A06699) does not want to calibrate to the 10 Volt level although 1 Volt is fine. The 10V adjustment pot in the 11177B reference assembly simply doesn't adjust far enough—I can get the reading down to 10.00020 Volts but no lower.

Just for the heck of it, I picked up another reference assembly from an eBay seller. It's an "A" assembly rather than the "B" the 3455 came with but it works fine and I am able to calibrate both 1V and 10V. 

The reference assemblies have a set of jumpers for "coarse adjust" so it should be possible to tweak the "B" version back into calibration. Does anyone have experience doing this? The service manual just says "return to the factory." It would be nice to hear from someone who has worked with these things before I start messing with the jumpers.

Jeremy

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