Krohn Hite 523 calibrator Alignment / Adjustment procedure

[Krampmeier]

At work we have an old Krohn Hite 523 7.5 digit calibratorwhich fails the calibration. It has been in spec for many years without any adjustment, and has now  failed. Looks like sending in the unit for factory alignment is not economical in this particular case. I did not have the chance to check the cal history yet, but I will do that in a month in order to see if there was a slow drift or a sudden jump.

Unfortunately, the manufacturer does not provide instructions on how to align the thing. Even the normal calibration (verification) routine is secret, you have to buy use the closed-source exe program, which was a PITA to get running... , Krohn Hite?

Has anyone found out how the Krohn Hite 523 can be re-adjusted? Are there special GPIB commands for calculating and storing the offset and gain values? I have not opened the unit yet, but I don't assume that it has any variable resistors for that purpose...

Any input on this unit, especially related to service and repair, would be interesting...
For example, one trap we found is that using the "sense" terminals seems to reduce the accuracy of the output voltage.

Thanks in advance for any hints! 

[little.tesla]

Sorry for resurrecting this thread..

I'm as well interested in any information related to the Krohn Hite 523 calibrator. Maybe in the meantime somebody was lucky to gather some additional information.
On the web there is only a datasheet and basic user manual available, without any other details e.g. adjustment (apart referring to the commercial calibration software)

[Krampmeier]

Some images for those still interested...
I don't have any updates regarding alignment of this device yet though.