Help with non-functioning HP-9825


I just picked up a clean HP-9825 - but of course it doesn't work.
The fan runs, the keyboard shift key lights, there are lights in the tape drive slot, but the display remains blank.

I'd appreciate any direction on where I should start. I have the Museum DVD and it has the 9825B service manual - I'll be printing it out later this weekend. But just wondering if there were obvious places I should start with first.

The unit says 9825B on the outside cover and 9825B inside the flip up cover over the printer, but also says it has 61670 bytes of memory. Does that make it a 9825T or just a B with more memory.

It also came with several tapes, but I'm assuming that I would probally need to rebuild the tape drive before attempting to use them (of course only after I get the basic opertion working first before playing around with the tape mechanism.

Thanks for your help. It should make for a fun winter project.



IIRC the HP9825 service manual is a boardswapper guide with no real troubleshooting info. You can get 'my' schematics either on the HPCC CD-ROM or from the Australian Site. I can't remeber exactly which version I covered, but I think all the boards will be included.

I would start by checking the PSU voltages, then check the processor clock (be warned, this circuit is somewhat unconventional, there is 'jitter' on the processor clock to reduce RFI emissions), then look for activity on the processor bus.


Hi Tony,

Thanks for the info. I think I do have the HPCC CDROM's somewhere, so I'll look up your schematics.

I'll have to get a friend to help me out with checking the clock. I don't have the test equipment, but he does.



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