We need assistance in diagnosing our HP 9815A calculator computer. If anyone can help us fix ours or locate a replacement HP 9815A, we will be VERY appreciative. Thank you. Frank Simpson, fbsimpson@pharmacy.wisc.edu , tel. 1-608-849-3382.
HP 9815A repair
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08-22-2007, 11:38 PM
08-23-2007, 04:33 AM
You can get 'my' schematics of the HP9815 from the Australian site. Somewhat strangly for an HP calculator, the 9815 is based on a standard microprocessor, a 6800. There are a few 'suprises' in the electronics, but nothing too strange. You don't give us much to go on. What does the machine do? Do you get anything on the display? What experience of electronics troubleshooting do you have? What test gear do you have access to?
08-23-2007, 03:55 PM
Thank you, Tom,
Switch in run mode
Once in the program mode, the display reads 0000 on the left, and 0136 on the right. There should be 432 programmable steps, minimum, not 136. Furthermore, our machine has the 001 memory and 002 I/O options. The 001 option should increase memory to 2008 steps. Again, not 136. On good days, I can program a few steps. For example, I can key in steps to recall numbers stored in A -> J registers, multiply, end, etc. But when I switch back to run, she does not run.
08-23-2007, 06:15 PM
Does the machine exhibit the same behaviour if you pull the 001 RAM option? Andreas
08-23-2007, 06:52 PM
Many Thanks Marais for responding. This forum is great!
08-23-2007, 07:31 PM
Dear Mr. Duell,
08-24-2007, 01:22 PM
Quote: If you want to be formal, it's 'Dr Duell', but 'Tony' is fine :-)
Quote: That '136' steps left is clearly wrong. I susect a RAM problem. Now, had it been a 9815S, I'd have immediately suspected the RAMs on the CPU board, as they're 2114s in that machine, and a more unreliable chip I've yet to see. But in the 9815A, they're 2111s I think (256 locations of 4 bits each). Given that it's a 6800 system, it's likely that system variables are stored in page 0, since there's a shorter,faster way to access locations there. So I'd replace those RAMs first.
08-25-2007, 02:26 AM
Dear Dr. Tony, |
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