probably the capacitor on the -5V rails is a problem here. fix -5V and you will get a display again almost certainly.
If +5V is working then the switching supply itself is functioning. I have machines with this symptom also, if a fix is identified please share. I have never recapped an M100 . Maybe I should be. On Fri, May 17, 2019 at 10:32 AM Josh Malone <[email protected]> wrote: > On Fri, May 17, 2019 at 10:22 AM Ed Graffius <[email protected]> wrote: > > > > ok, opened it up and the nicad has 4.8ish volts on it. > > Good. I'd plan to remove or replace it soon anyway. > > > Theory: lack of -5v prevents the LCD from lighting up? > > Yep. Check out the M100 service manual > (https://ftp.whtech.com/club100/doc/m100ServiceManual.pdf) for > troubleshooting steps on the power supply. It's a great reference. > > > > > btw - the <enter>, 'B''E'E'P' <enter> works, so that means the CPU is > CPUing? > > Yep. Display issues only. Should be a simple fix. Congrats on your > acquisition. > > -Josh >
