|hp 25 amnesia|
Message #1 Posted by Pierre LANCELOT on 8 June 2002, 4:56 p.m.
I've rescued a hp25 from the trashcan where it had been thrown by a colleague (#1509s36887).
After taking apart, cleaning (very beautiful white crystals in battery compartment) with alcohol & plugging a new NiCd inside, it appears that :
- display & kbd in working order
- all basic functions work :arithmetic ops, stack, trig ...
- data : none of the Rx registers memorize anything : RCL returns zero
- instruction : PGM mode doesn't work : the pgm counter increments but any typed instruction displays as "goto 00"
It looks like a failure of some memory to store data/instruction (is there a common place for both) ?
There are 2 chips at PCB top :
- AMI 7523SH 1818-0153
- HP 1820 1382E
The 3 chips at bottom of the PCB are :
- AMI 7523B1 1820-1523
- AMI 7524NE 1820-1564
- AMI 7525CL 1818-0154
I'm completely ignorant : could somebody describe the respective part of each, which one is guilty ? Is there any way to fix it ?
Is there something else I could check (capacitor, transistor ...) ?
Thanks for any help.