I did find some time last evening to investigate my sick M100 further. All A/D signals seem to be propagating through the buffers/latches properly and make their way to they ROM. The ROM /CS is also toggling for a while after reset is pressed so it does seem it is being accessed. It just occurred to me though that I failed to check the various RAM /CExx bank select signals.
I guess after checking out the RAM /CExx signals I could get out my little logic analyzer and monitor the data buss after a reset and see if the ROM seems to be returning the correct data, or I’ll just build an adapter, so I can read it in. I also just recalled that my little eprom programmer can test many 74xx style logic chips so if I run completely out of ideas I can do a semi-shot gun approach and pull the glue logic chips and test them. Jeff From: M100 <[email protected]> On Behalf Of Fugu ME100 Sent: Thursday, May 3, 2018 10:29 AM To: [email protected] Subject: Re: [M100] SPAM-LOW: Re: New member - question on 'half' alive Model 100 Have you been able to replace the NiCd? Another thought would be to check the ROM socket is really making contact with the ROM. Over the years the spring contacts might not be so good. You could try plugging the ROM into a turned pin socket and then into the sock just to make sure there is a good contact.
