This is a 20 amp switching power supply for their 12 volt ham transceivers.
I used to leave it on 24 hours a day on receive pulling less than an amp
with no problems but about a month ago it started to shut off. You have to
turn it off first and wait about 15 minutes and it'll come back on,
sometimes for an hour or longer and other times for 5 to 10 minutes. After
it goes down you have to turn it off and then wait 10 to 15 and it'll come
back for an unpredictable time. It doesn't seem matter if it been on for an
hour or sometime 5 minutes, it'll shut down. It doesn't seem to be a cold or
heat problem and flexing the board or tapping components won't turn it off
or make it come on quicker. I don't have a schematic and can't find one.
It must have some kind of logic that senses something and makes it shut down
and then time out. One thing I have noticed is that if I turn it on when
its not ready to come on I can hear a very, very faint noise (like static
discharge) that goes away as soon as the switch is turned off. It has a
TL494CN. Any tips appreciated.

--

73
Hank WD5JFR