I've been looking at the forums to find this problem I'm having and I'm stumped.

It's state:
It was working fine for the part two years (I got it used, but the previous owner stated it had no problems with him either) with no problem what so ever.

About a week ago, I turned my rear projection on and it immediately went back to standby. I unplugged it and let it set for some time, and then plugged it back in, it auto-turned on, and then went immediately to standby. Okay, something is wrong I thought. So I pulled the back cover and on the AC board (to the far right if you look at the back of it, a LED (location D118) was lit up. No other lights I could see. Seeing other posts, I removed the power board and found numerous cold solder spots. I corrected that problem and then reattached the board and powered on the set, it went back to standby again immediately. I looked again and now I found that besides the led D118 was lit, the power board had blown fuse FU206, I replaced the fuse and plugged it back in, it blew the fuse again. Checking the schematic, it led me to believe that the AMP board was the fault (specifically the STK392-040s). A suggestion in one of the forums was to remove the STK392s to see if it blew the fuse afterward. I did so, and I found a ton of cold solder joints on AMP board also. I corrected them and then reattached the amp board with the STK392 missing. It powered up and was working, minus the convergence was all jacked. I didn't bother to do anything, so I powered off the set and ordered the STK392 replacements (the exact ones, not generics). When the new ones arrived, I installed them and then plugged it back in. it went back to the standby light immediately, and the LED D118 was lit up again. NO other leds are on any of the other boards. The forums mentioned to check for an led on the other boards so I looked with the lights turned off in the room. Nothing. I'm baffled on where to go next.

Please help!

i went and took the power board back off and found a couple more spots that I missed. Right now, i'm going through the deflector board and finding a ton of cold solder spots on it. really weird, how did this RP work with all of these cold solder spots on the boards.
:rolleyes:

when i found those spots on the power board, I desoldered and tested the caps and the diodes with my trusty dmm in the line of going to the amp board. they tested fine and are working.

Just because a solder joint is "cold" does not mean that the two surfaces are no longer in contact.
This problem apparently is caused by the fact that early generations of leadless solder have a tendency to separate from one of the surfaces after 3-5 years and therefore the joint becomes a "cold" joint.

true, i suppose what I call a cold solder joint is actually a loose component that appears to have separated itself from the board at the point of solder. it may have some solder on it but none the less, it's not making contact or contact that is intermittent.

as far as the update:

i managed to see a dimly lit light on the deflection board at the point of which it shuts back down to standby (it trips the safety, actually). I took the deflection board out and found yet more (now changing my wordage from "cold solder spots" to "loose components" :rolleyes: ) loose components around the flyback. I'm in the process of securing (resoldering) the components and checking over the others. this makes board number 3 with the same type problems.

my father in law says junk it since I've put all this time in it and nothing is happening. I really liked this rptv. the picture was better than his and he has a pro-720.

the cost of the boards is phenomenal, so this is sorta my poor man's diary to seeing about fixing it.

I agree with your loose/intermittant connection definition. It is what I should have called the problem caused by the ageing of early generations of leadfree solder.

well, I've since updated the solder points on the deflector board and reinstalled it. now when it shuts back down (trips the safety) into standby, the deflector board led doesn't light briefly. but my pioneer still does what it did from the start, still goes to standby. at this point, I'm at a loss. I checked everything I can think of and nothing has worked.

the state of my pioneer sd-641hd5:
the unit when plugged in or switched on from the main switch in the front, it switches to green and then trips the safety, thus causing it to go back to standby. I've re-soldered the power board, the amp board, and the deflector board thus getting rid of various problems, and replaced the convergence ICs.

in my troubleshooting, if I removed the convergence ICs, the unit actually powered up and worked, with the problem being the convergence is all jacked. replacing the ICs caused the original symptom to appear. no fuses are blown, and now after re-soldering the deflector board, no lights come on other than that original light on the ac power board toward the top showing that the safety was tripped.

any suggestions are welcome, or should I just part it out and recoup my losses?

If it is tripping the safety then IMHO some circuit in the system is drawing too much power. It appears that there a may be shorted capacitor on the convergence board that does not have an effect when the full convergence circuit is not in use.
It has been many years since I actually repaired TVs so hopefully someone such as Hammerdwn whose repair advice is excellent will provide other assistance in this thread.

i checked the 25v and -25v feeds from the power board prior to the unit tripping the safety. My VMM showed a total mix of volts from mV to maybe 2-3V. Then it trips. I checked other points on power board and they hit their rating. some are 40v, 9v and 5v. They maintain it rather quickly, but the 25v/-25v freak out due to the load.

the convergence ICs are new. i'm having to find time to check the boards as my 3yo keeps intterupting me. a couple of things I found bother me about the votages I found, mainly one called C+5v, when it comes out of the power board it shows 11v. but the convergence board gets it down to +5v after running through a power resist and then a couple diodes. maybe nothing.

something else I found: when the convergence ics were desoldered. the RPTV came up, and the picture was wacked as expected, but another concern was no sound. it looks like the convergence board has a bit more than convergence as a problem. so I'm going to have to track that problem down too.

i re-capped the power board (replaced all capacitors) and desoldered the 2sk1938 MOSFETS and tested them. everything tests fine. I also pulled the ac power board and tested the bridge rectifiers to ensure it wasn't a load issue. they passed also. so it appears to be after the power board, i'll re-check the convergence board going forward, not many caps on the conv board.