Greg Mayman wrote in a message to Roy J. Tellason:

 -=> Roy J. Tellason said to Greg Mayman
 -=> about "POWER SUPPLY" on 12-07-03  04:05.....

 RJT> Yes,  it's proving to be the case here.  Concurrent with hardware
 RJT> issues,  too.  Until yesterday I never saw a HD where just putting the
 RJT> power connector in would prevent a system from powering up at all,  so
 RJT> I guess there's a problem in there,  and I have a thought or two on
 RJT> that subject,  like maybe a shorted cap or similar?  We'll see,  if I
 RJT> can find the time to mess with it. 

 GM> A dead short is usually one of the easiest to find, mainly because 
 GM> it is so drastic a fault.

One would think so,  only this one didn't show up with an ohmmeter.  I
suspect that something on there is breaking down under voltage.  I need to
be able to apply the two voltages separately,  and see what happens...

 GM> Intermittents are harder, but the ones I hate are where something
 GM> just draws more current than usual.

Yeah.  I don't know what this was,  though I may find out.  If something
does draw more current,  maybe something in there is gonna get hot?  We'll
see.

 GM> Some years ago I tried to isolate a fault on a digital delay unit
 GM> (used for telephone talkback on the radio) where the 5V regulator
 GM> suddenly was running a lot hotter than usual. I never did locate
 GM> the cause due to not being able to access the unit for most of the
 GM> day, as it was being used on air.

 GM> Fortunately it was still working alright last time I heard...

Hmm.

 RJT> Yeah.  At least I've collected a ton of schematics of assorted simple
 RJT> little circuits,  and may have the inclination to play with some of
 RJT> them.  I like the simple approach,  when it can be made to work.  Some

 GM> I've collected quite a few. If you're interested in getting more,
 GM> you could take a look at Electronic Projects Online...
 GM> http://www.electronic-projects.net/index.shtml

I'm not sure,  but that may be where I've collected some of them from. 
There are so many sites that I've lost track at this point.

 GM> That's one of several sites with interesting circuits, sometimes
 GM> very trivial, but occasionally novel and interesting.

I'll try and remember to take a look...

Would that guy have a bunch of solar stuff on there?  If so,  then I did
snag a fair amount of stuff there.

 RJT> stuff gets just too elaborate,  though.  There was one design I can
 RJT> remember where a signal went in the order FET -> optoisolator ->
 RJT> transistor -> SCR -> bridge (!) -> triac, which I thought was a bit
 RJT> much... 

 GM> I think I know what they were doing. OTOH it could probably have
 GM> been simpler.

What do you think they were doing?

 RJT> I've surely had enough of that,  stuff that isn't fixed is either
 RJT> going to get scrapped (like I need more parts!) or just tossed.  A

 GM> I still have a 5-inch National Ranger TV from about 1971 that has a
 GM> short in the p/s, probably a diode broken down. It's just been
 GM> waiting until I can find time to dig into it far enough to get to
 GM> the diodes, which is ###### awkward because of the way it's
 GM> built. But now I think I may have lost the screws for the case.

And by now it probably needs some caps,  too.  :-)

 GM> My original intention was to connect it to the video output of the
 GM> VCR, so I can monitor the VCR without switching the big TV away
 GM> from the program we want to watch. A very handy feature when you
 GM> need to copy something fairly long from a tape that has other stuff
 GM> on it as well.

That's one of the reasons I still have a couple of small composite-input
monitors around.

 GM> But the local s'mart is selling 4" or 5" TVs with AM/FM radio for
 GM> only $30.... maybe I will scrap the old Ranger...

That's the kicker,  stuff that's out there is getting *so* cheap it's
hardly worth repairing much any more.

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