Hi Welcome to the Model T world.
Just a couple of quick things: 1. Have you tried a cold boot to clear out any bad data in the memory? 2. Is the LCD contrast adjustment working? 3. If the LCD is going dark it usually means the processor has reset it, if it did not there would be garbage bits on the LCD, and the beep is a normal part of the boot. Once it is powered on hit return this should enter BASIC, then type beep and enter. The unit should beep. This would indicate the unit is booting but the there might be a problem with the LCD. 4. You could also check the Electrolytic Cap on the reset line it may of leaked too which could impact the reset timing. 5. The new NiCd might need some more time to charge up. From: M100 <[email protected]<mailto:[email protected]>> on behalf of Jeffrey Birt <[email protected]<mailto:[email protected]>> Reply-To: <[email protected]<mailto:[email protected]>> Date: Sunday, April 29, 2018 at 3:19 PM To: <[email protected]<mailto:[email protected]>> Subject: [M100] New member - question on 'half' alive Model 100 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
