|Re: Dead HP97, any ideas? TIA|
Message #5 Posted by Viktor Toth on 29 Feb 2000, 7:09 a.m.,
in response to message #3 by Dr. Ido
First of all, make sure that you aren't trying to use the machine with the HP wall plug, but no battery installed. It's the battery that both stabilizes and regulates the rectified voltage, so without it, the calculator will not work (may even end up being damaged, but I don't think so; it's the continuous memory models that get more easily fried this way.)
The battery voltage is indeed 4.8V nominal; 4 NiCd cells in series. You can use a standard 5V power stabilized supply attached to the battery terminals if you have no battery pack.
No flicker means that you probably don't have a clock frequency. Which may mean that only that part is fried, or it may mean that everything is fried. It's been a while since I last took one of my HP-97s apart, so I don't exactly recall how the clock frequency is generated, but I'd just start poking around with a 'scope, looking for signs of life; I'd also check any discrete components, like diodes and transistors, in the hope that the problem is with one of those, because those are relatively easy to diagnose and replace.
Then again, I'm just a programmer, and you know what they say: beware of programmers who carry screwdrivers! :-)