The Museum of HP Calculators
HP Forum Archive 10
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Message #1 Posted by john on 19 Jan 2003, 10:15 p.m.
Does anybody have a non-functional example of this
calc. that they are interested in parting out?
I think I need a spare keyboard card, maybe more.
Almost all of the keys give incorrect outputs on the display .
|Re: model 9820a|
Message #2 Posted by Tony Duell (UK) on 20 Jan 2003, 3:46 p.m.,
in response to message #1 by john
Alas the 9820(and 9821) is the one series in the 98x0 family I've not worked on. But I believe it's similar to the 9810, and that machine I have pulled apart.
My expeirience suggests that keyboard/display problems are often caused by logic problems on the I/O interface PCB in the processor section. In the 9810 and 9830, this is a 09810-66511 and has 2 brown handles. AFAIK the same PCB -- in fact the same 4 PCBs for the complete processor -- is used in the 9820 as well.
I suspect this card can get easily damaged by plugging things into the I/O slots with the power on, etc. It certainly is directly connected to the I/O backplane.
If you want to try some component-level troubleshooting, then I can possibly help you (you'll need a 'scope or logic probe and some experience, though). Take a look
at the part numbers of the PCBs in your machine. If they start 09810 or 09830, then there's a good chance I'll know how to fix them.
What exactly is the fault. You say some keys do the wrong things. Do they do the same thing as other keys, or do they behave strangely (I had a 9810 where pressing the mode select keys could randomly change the LEDs, for example).
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