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HP 9845B - S/N 1838A01653

General Notes

Donated 4/2018.
Non-functional when received - no monitor, no power supply.

Initial Inspection

Includes Eventide WMAZ-4 RAM board in undocumented WMAZ-4(3) configuration, corresponding to 3 HP 128K memory boards. Supplemental ROMs from Structured Software Systems with PUP+, MMS and CMD are installed.

The Option 100 power supply was removed from 9845T S/N 1838A06653 and (re-?)installed in this machine. Initial power up resulted in a single beep, fan noise and power LED lighting on processor but no video output.

Voltage readings from the power supply test points were as follows:

Other than the +12 value, everything is within specification (+/-17V and 18V call for a +/-1V variation, but I'm not worried about a few hundredths of a volt). This is pretty amazing performance from a 40ish year-old power supply.

Now on to the +12V problem …

Repair

Images