|Re: HP25C died?? - AM radio diagnostic tip|
Message #6 Posted by Andrés C. Rodríguez (Argentina) on 4 Apr 2004, 12:19 p.m.,
in response to message #1 by Walter B
It is possible that your calculator have suffered severe damage, as many posts had suggested before; but I encourage you to read (in the MoHPC Articles forum) an article by Katie Wassermann about Woodstock common faults and repair, since there are some repairable problems (clock signal malfunction or noise) which may cause symptoms similar to your description. I have worked with an HP27 (Woodstock) from a friend which seemed to have been damaged, but after some warming-up and some battery discharge (!), it started to work fine.
Diagnostic tip, specially useful for LED based calculators:
Put your calculator (powered by batteries) near a working AM radio receiver, turn the calculator on, and hear the electrical noise induced in the radio. You may need to play a little with the tuning dial, but there is no need to be precise about tuning a specific frequency.
Press different keys and hear the noise changing. If the noise and the changes are there, then it is not a case of "no brain activity" death (flat EEG): At least the power supply is partially working, there are clock pulses and keyboard scanning signals (which also are closely related to display operation). As the keyboard and display scanning is run by firmware, at least some CPU and ROM activity can be confirmed.
You may still have noisy clock lines, clock instability, faulty RAM, faulty display drivers, etc.; but this is a simple , cheap, fast and safe test you can do by yourself and after this first screening you can take better decisions about asking for help, validate diagnostics or try repairs by yourself.