Hi All,
I'm working on a M100 that was desperately in need of having the electrolytic caps replaced. That job was done, and the mess cleaned up. That being said the power supply section is not working. At one point it did start working briefly and was outputting a steady 5V and -5V. The memory battery is charged: VB = 3.3V VL ~= 5.5V all the way to Pin 4 of OT2. I ohmed out the +5V and -5V rails to make sure they were not shorted. Measuring across secondary of the transformer, OT2, pins 7-9 with scope shows a blip on power on. However, T21/T22 are not oscillating. Ohming out the transformer shows both primary and secondary seem OK. I have done the simple things like checking the diodes and transistors and double checked that the leaking caps did not cause any broken traces. It looks like if I remove T20 I can isolate the auto power off circuitry. I'm trying to figure out what T27 and T28 do as well as figure out what steps to take next. Since it briefly worked it could be an intermittent short/open or perhaps a component is right on the edge of tolerance and not letting it start to oscillate? Open to any ideas. Thanks, Jeff Birt
