Datron 1281 Meter Repair Help

[starjohn]

I am working on a Datron 1281 meter.
DC voltage calibration at 10v functions ok, but the Internal source calibration failed.
This Meter has the following errors after Internal source calibration.
Error codes:
2202 1Kv  Range zero magnitude test (P028).
2192 100V Range zero magnitude test (P021).
2162 10V  Range zero magnitude test (P006).

Is there anyone that has experience in repairing these instruments?

Thanks,
John