DMM6500 Keithley Error Code 1153

[faster91]

I have a Keithley DMM6500 6.5 Digit Multimeter. Few days ago I encountered in the error 1153.
The Error Code 1153 indicates a problem with the internal power supply. I tried to update the firmware and checked the voltage at the source, but it was ok.

Does anyone have any suggestion?

Thanks.

[m k]

If machine can sense more it must also have more sensors.
Those sensors can also go faulty and then report incorrect problems.

Manuals I found were not helpful.
Is the code a single number or something packed?