I hope I've come to the right place to get some helpful hints.

I am working on a Mitsubishi TV, model CS-2056R, made in 1988,
specifically, the IR remote receiver circuitry.

The remote function for this unit began failing some time ago. At times,
it would just up and quit working and then just as suddenly, it would
start working again. At first, there did not seem to be a pattern, but
after some months, one appeared. The remote would never turn the machine
on or control it for the first 10 minutes or so, sometimes for much
longer but mostly only for the first ten minutes. After this "warmup"
period the remote control function would kick in, but it would die and
come back to life without hint or warning.

I finally decided to see if I could fix it. Without going into detail, I
am 100% sure that the handheld unit is not the problem. After searching
the web and the newsgroups and spending several hours tracing the traces
on the tuner board of the TV and taking readings with a multimeter, I
decided to try changing some of the larger electrolytic caps used to
filter the AC and anything over 100 microfarads or 50 volts (BTW, I
don't do this stuff for a living, just a part-time hobby). I also
changed a resistor that looked like it had failed.

I also took apart the IR receiver module and changed the three tiny
electrolytic caps within. About this time the remote function ceased
entirely. No matter how long I let the unit warm up, the remote would
not function.

Today, after more web and newsgroup searching, I decided to buy a four
dollar Radio Shack IR receiver module and guess what, it worked! I
mounted the Radio Shack module on the tiny stock IR receiver circuit
board and soldered the three pins to the appropriate spots, held my
breath and hit the "power on" button on the remote and the TV turned on.
I watched an old episode of Perry Mason and then turned it off.

Now, some four or five hours later, the TV will not respond to the
remote. The Vcc voltage to the IR receiver module is 5 volts and the
Radio Shack unit is rated at between 2.4 and 5.5 volts.

At this point, my next idea is to change all the little electrolytic
caps and maybe any small transistors that I find in the IR receiver
circuit. The last step will be to change the 42 pin IC that receives the
signals from the remote and activates the appropriate circuits. I don't
think that is the problem, though as everything worked okay when I put
in the new IR receiver module.

I have a sneaking suspicion that there may be some AC leaking into the
IR receiver circuitry, but I really don't even know if that is even a
valid concept.

If you have read this far and think you may have some insight, please
feel free to post it as a reply to the news group.

Thanks,
Jack