Update:
I got some time to pull this out to look at it again and after sitting,
it is just working again. Several power cycles so far.
Scratching my head here.
I found that I have a couple of dead keys on the keyboard I am going to
need to fix.
Scott
On 10/2/2025 10:06 PM, Scott McDonnell wrote:
So, if you recall, my newest M100 would not initially power on but I
had found that if I left it on for a long time, it eventually would
power up. Suspected caps or nicad.
Earlier this week, I replaced the nicad and recapped it. It wouldn't
power up after that but I discovered a dirty power switch. If I
wiggled it, the M100 would power up. So I cleaned the switch with
deoxit and confirmed the switch is working perfectly now.
But, again, it would not power up. So I sat down with a DMM and an
Oscilloscope to troubleshoot. Of course, I checked over all of my
solder joints, looked again for board damage. There was some damage
under C85 from leaking, but continuity checked out.
I noticed that the switching frequnecy was completely dead. Probing
more, it eventually came up, but was less than a volt. Reflowed joints
in the oscillator portion of the power supply even though they looked
fine and suddenly I got a nice 5V squarewave and it powered up. Worked
for a few power cycles and then nothing again. I am suspecting cracked
ceramic caps now, but thought I would ping the group with more
experience.
Oh, I also noticed the transorb (D27) was getting very hot. I removed
it and it measures 47ohms. Not certain if that is normal, but for now
I left it out.
Scott
