Hello,
I got a Model 100 a while ago and just got it out to do some serious troubleshooting. After reading what I could find online I removed the NiCad battery (bad) and replaced C82, C85, C49-50-54-55 as they had all started to leak. The extent of the leakage was small and no visible damage other than a small path of silkscreen coming loose as I cleaned it up. I now have all three supply voltages from the power supply. When turned on I get a solid black LCD and a brief click from the speaker. I checked that the processor is getting a clock and all the address/data lines are changing states. The solid black LCD would indicate, based on previous experience, that the LCD drivers were not initialized. I looked for PA1, etc. signals from the 81C55 and found they were not changing state. The two signals that looked odd on the 81C55 were the lack of /CE and IO/M changing states. I followed the /CE back though to M16 and found that it too made use of IO/M which was not changing states. Looking back at the processor the IO/M was indeed not changing states there either. I thought this could mean that the processor was running garbage code. Looking at the main ROM, M12, all A/D lines are toggling as is the CS. I pulled the option RAMs out just in case, but no change. I then noticed that if I power cycle or press reset the processor might briefly run and then stop or might continue to run. No matter what I do not see the IO/M never changes state when running. All lines on the main ROM seem to be behaving normally though. I am rather stuck at this point and hoped someone might have had a similar experience? I have scoured the web and have not found much in the way of repairing the Model 100 other than the NiCad and leaky caps. Any help appreciated. Jeff
