Hi Clinton, Get the M100 service manual PDF online, it will have steps for checking the internal power converter. It is a discrete set of transistors, not an SMPS chip, and I have read in at least one place that it is not known for being particularly reliable.
A quick check, the upper left of the board is the PSU area and you should be able to find ground, VCC (+5) and VEE (-5) test points. -- Erik On Thu, Dec 18, 2025, 10:10 PM Clinton Reddekop <[email protected]> wrote: > Hello all, > > My Model 100 has broken somehow. I'm hoping for some advice either on > troubleshooting or somewhere I could send it for repair. > > > My model 100 was on, I think in the BASIC screen but not running a > program. I turned away for a few minutes and when I turned back around > there was nothing on the screen. It was running from an AC power adaptor. > I have checked it with a multimeter - it is 6V. > > Turning it off then on again didn't work. > > Turned it off and removed my REX module just in case. Still nothing when > turned on. > > Turned it off. Removed QUAD RAM module. Split the case and put back an > original 8K module in the base location. Still no workie. > > I have tried running from batteries. I have tried reset. I have tried > holding ctrl and break while turning it on. I have tried turning it on, > pressing <enter>, beep<enter> - it doesn't beep. > > Adjusting the contrast dial makes all the pixels darken a bit, just as it > would normally do for pixels that aren't on. But the screen has no pixels > that are on. > > > Any help is appreciated. > > Thanks, > Clint >
