HP 9845B: Any expertise out there?


I am currently warming up/drying out a 9845B that has been in 'inadequate' storage for some years.(plus the dual 8 inch disk drive that goes with it) There is a fair amount of operating/programming literature with it but there is virtually nothing in the way of servicing/technical info.
Is there a source of any technical info on these beasts anywhere? I am reluctant to power it up without at least some basic information on hand(if only to defeat Murphy)but I may just have to do that (cringe!) if I can't find any.




You might have already powered the machine on in the meantime, but if not, there is a couple of hints I can recollect:

1) I think the only user manual shipped with the HP 9845 that concerned also the hardware was the "Getting Started" and don't remember anything particularly interesting mentioned inside.

2) You can run the machine even with virtually all peripherals removed (or disconnected), including namely the tape drives, all ROMs from the drawers, all interfaces (obviously), and the whole CRT unit. Then you should wait a minute after powering the machine up to pass through the
internal tests, type PRINTALL IS 0 <Exec>, switch the PRT ALL key on, and, for instance, type LIST <Exec>. If you are lucky enough, this will print the free memory capacity on the internal printer.

The above (except for the ROMs) is positively applicable to HP 9845A, but, according to my dim memory, I saw the same with HP 9845B, too. Needless to say, this all is meant to minimize the potential damage in case something is wrong with the power supply.

3) I think the first reasonable thing after powering up is to check the test voltages on the top of the power supply unit.

4) If the machine is / was dirty, personally, I would chiefly fear of a possible discharge upon the HV transformer in the CRT unit. (You can then hear a sort of gentle ringing even in case the image on the screen still
looks undistorted.) After a while, this is usually irreparable, as the discharge quickly burns in a path on the transformer's surface.

5) One typical failure are burnt lamps (miniature bulbs, in fact) in the tape drives that serve to search for the tape beginning. Hence, if you can't see the light inside the drive, don't insert a cartridge there or you wind its tape out.

6) Also, rubber covering the shaft in the drive that propels the cartridge's central roller has often dilapidated in the course of time.

In case you have no access to a more reliable source, I hope this may be of some basic help. If you succeed, I would be glad to hear more from you. Strange enough, I can't get in touch with anybody still running an HP 9845B worldwide, and, for the moment, don't know how to get beyond the "MEMORY TEST IN PROGRESS" message hanging on the screen of mine and probably indicating the LPU (Language Processor) failure.

Best regards,
Petr Horsky

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