Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed but.

[richardjefferson]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

thanks.

update - its powering on and off frequently. Although inconclusive based on the random behavior of the board with out outside stimulus, Tapping on one of the 2 long heatsyncs in the middle of the power board have a definite impact on the tv shutting off.

half the time, tapping the board results in no change, other times its a tap on one of those heatsyncs and its instantaneous. interestingly, when it shuts off from that action, it seems to turn itself back on.

Tapping on the main board does not seem to have any effect.

[tom66]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

update - its powering on and off frequently. Although inconclusive based on the random behavior of the board with out outside stimulus, Tapping on one of the 2 long heatsyncs in the middle of the power board have a definite impact on the tv shutting off.

I did not think to consider originally, but this generation of Samsung power supply has many cold solder joint issues. Inspect the board for cold solder joints around the devices mounted to the heatsinks (solder side only), they look like this:
http://www.justanswer.com/uploads/Ed...oint_small.jpg
http://upload.wikimedia.org/wikipedi...oetstellen.jpg

To fix them, wick up the old solder and apply new solder (ideally leaded, not lead free.)

[richardjefferson]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

Thanks for the pics of what to look for. I inspected the board and did not find any cold solder joints. I took some high res pics of the back and have attached them. I can actually get a closer look with these then with my magnifying glass. The worst solder joints are from the 5 CAPs i replaced.

[richardjefferson]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

pics for back of board

[tom66]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

Can you take some around the bottom of the board near the largest transformer on the board?

[richardjefferson]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

attached are 6 pics.

3 pics run from where the largest transformer is attached to the end of the board.

the next set of pics starts in the middle of the board and run all the way across. there are 3 transformers in this row.

[tom66]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

I don't see anything obviously wrong, but please re-touch all the joints on the transistors instead and re-try the tapping the heatsink. Remember to use an insulated screwdriver - electric shock risk otherwise!

[richardjefferson]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

When i retouch the solder joints what procedure do i use? :
A. heat the joints and suck up liquid then resolder?
B. heat joints to allow the solder to reflow and do not introduce any additional solder?
C. other.

[tom66]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

Clear off the existing solder (suck it up) then apply new solder.

[richardjefferson]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

my soldering skills at the component level leave a lot to be desired. im using a variable watt gun from 20 to 50. even at full power, i have a difficult time getting the solder to liquefy enough to suck it up (im using a vacuum solder sucker). Same problem resoldering. was using a 60/40 rosin core solder .050" and .062 diameter. i noticed the tip of the iron melted or broke away.

anyway, back to the tv. i put the board back in. it powered up and turned itself off in less then a minute. it powered itself back on after about same amount of time, then shut down again after about 30 seconds.

would not power on again right away. i let it sit for about 10 min and it powered up again. stayed on for less then a min and turned off and did not come back on.

5 min rest and i could power it up again. stayed on for about 30 seconds, turned off, turned itself back on turned off. all under a min.

tried to tap heat syncs in the first few seconds and it did not seem to have any effect.

any thoughts? time to cry uncle?

[tom66]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

Obviously when it warms up something is falling over.

You need to heat up parts individually and possibly freeze spray them to locate where the fault is.

I do not know where the fault is but using some simple deduction you can find it.

[CoppellTVRepair]

Re: Sanyo DP50747-00 (Samsung Power Board LJ44-00132A) - Thought i had problem fixed

I will start with honestly saying I did not read the whole thread up to this point.

But today we've added LJ44-00132A and LJ44-00132B in the list of boards that we offer a repair service for and - when possible - an exchange program where you can buy a working board and then send yours back for credit.

This means we've repaired a few boards of each type and feel confident we can process a board within about 2 business days of receiving it; of coruse we can't always repair them, but if we get to the point of offerring a repair that means we believe we'd be successful way more often than not :-)

Anyhow, hope this would help someone in need:

http://www.coppelltvrepair.com/p/830...owering-on-etc

If you want to find if a board is available for purchase/exchange, just go www.copppelltvrepair.com and search for the model (LJ44-00132A, LJ44-00132B etc.)

Thank you.