I had a RAM problem with my Model 100 when I first got it. It seemed to work fine initially, but attempting to paste text resulted in odd characters appearing, and the amount of free memory slashing drastically.
Various people were very confused as to why this was happening, but a bit of experimenting also revealed the machine would crash with memory only partly full. This suggested corrupt RAM somewhere. My machine (UK spec, no modem) had a soldered RAM module and 2 socketed ones. By a process of trial and error, using it with 8K, 16K and 24K in all available permutations, I was able to (thankfully!) work out one of the socketed modules was the problem. It's now out the machine, and I've bought 2 modern modules to get it up to 32K. I've had no problems since. Lee On Thu, 28 Dec 2023, at 17:59, Eric wrote: > > Thank you everyone for the quick response! > > When I power up the computer, all pixels are on and remain dark (LCD is > entirely "black"). > > Contrast potentiometer: Seems to work as intended. The display will lighten > or darken as the potentiometer is adjusted. > LCD PCB: No signs of corrosion and/or damaged traces. > ROM: I'll ohm out the traces to see if I can find any broken connections. > Otherwise, are there any other troubleshooting steps I can take? > RAM: Jeff, great video! Thank you for sharing. The M100 Test Harness sounds > like an ideal tool. > I have limited experience with a logic analyzer however it looks like a fun > challenge. I'll try to duplicate your setup but I may need some tips on how > to configure the Saleae software... > > Eric > > > On Thursday, December 28, 2023 at 08:17:02 AM PST, Josh Malone > <josh.mal...@gmail.com> wrote: > > > On Thu, Dec 28, 2023 at 10:35 AM <bir...@soigeneris.com> wrote: >> When LCDs with these types of LCD driers first power up they turn on all the >> pixels. You will see this even in brand new ‘modern’ dot matrix LCD module >> (on the new LCDs the multiline modules tend to only make the first row black >> on power up.) Only after the computer sends a rest command to the LCD >> drivers they will clear the screen. >> > > Ah! Okay, I misunderstood that process then. If the driver ICs themselves set > every pixel then I agree it sounds like the machine is not running code then. > Thanks for clarifying this, Jeff. I appreciate it. > > -Josh > > > Lee Osborne West Lothian, Scotland 07960 096282 leeosbo...@fastmail.co.uk www.journeyman.online/services
