I'll describe a scenario that once really stumped me. When trying to power up the M100, I found it would start and instantly stop. Very strange. I traced it to the /LPS signal triggering a soft shutdown (like POWER OFF).
So, the implication is that it was a defect somewhere not related to the power supply, that was causing the power supply to shutdown. I will also say that I never really fixed it; I set it aside. The point is, there are system level feedback loops that can make a power supply appear to be defective. If the power switch is ON and T20 is also biased ON (meaning M28 pin 13 is HIGH) then it is being shut down by either RESET or PCS. On Mon, Oct 19, 2020 at 6:46 AM Charles Hudson <[email protected]> wrote: > My apologies. Apparently I haven't been clear in describing the problem. > > I have three "slabs": It is my Model 100 that is not functioning > properly. It will sometimes boot but mostly does not display any life when > I hit the power switch. > > I have verified that its AC adapter is the proper polarity and puts out > > 6VDC, that the AA alkalines are fresh, that the memory backup battery has a > full charge and that the memory battery switch is set to "on". > > I have also verified that in spite of these facts the CPU is not > outputting a clock signal. There was some question whether I was measuring > the clock signal properly, but I was able to demonstrate measuring the > clock signal on my Model 102. Using the same frequency counter and > technique, the Model 100 does not display a clock signal. > > The reason for this appears to be that the +5VDC supply to the CPU is only > +0.23VDC. The question now is what is causing this to occur. Somewhere > between the AC adapter's input jack and the CPU power is being lost. > > It will be a formidable task for me to identify which of the components, > which number in the hundreds and include capacitors, resistors, diodes, > transformers and more, are failing. But I'm learning as I go, and I thank > you all for your suggestions. > > -CH- > > > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> > Virus-free. > www.avg.com > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> > <#m_-5604703377747324575_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> >
