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

[tom66]

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

On a Samsung, a HIGH (>2V) on the PS-ON means the PSU is to be switched OFF.
Whereas a LOW (<1V) indicates the PSU is to be switched ON.
(Note - in between 1V and 2V is undefined, could be either.)

Since it is a signal from the main board (with the av inputs on it) to the PSU, it is most likely an issue with the main board.

[richardjefferson]

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

I found a replacement main board for $120 usd. Do you think that should be my next step?

im still scratching my head with the difference in behavior with the TV on the floor face down vs on the wall. I should mention that the TV hangs above a gas fire place and gets a lot of heat, however it has worked fine the past 4 years in the same location.

i do have schmatics for the main board but ive no clue how to read them.

[tom66]

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

Can you share a picture of the main board?
This is of course a Samsung chassis (power supply, sustain boards, plasma panel, etc.) but with a Sanyo main board. Sanyo have good reliability -- except with their main boards! Which seem to be a common issue...

A common issue we are seeing more and more is solder joints on the large processors failing, due to environmental restrictions on lead. Lead is vital for the performance of solder but since it cannot be used, problems are occurring with previously reliable systems.

It is often possible to fix the problem, at least temporarily, with a reflow, which essentially involves baking the main board at 225°C for a couple of minutes, with liquid flux around all main processors.

Also there's likely a part # on the main board -- use that for locating parts instead of the model number. Be aware the 42" main board may not work with this set as the 42" panel is most likely 1024x768 and the 50" is 1365x768.

[richardjefferson]

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

i just took 4 pics, 2 with flash and 2 holding a light. can you see what you need from these or would you like a better close up?

I found replacement boards online. the sticker is on the side of the tuner and the designation is J4DE Main. The rest of the numbers are MSB2MM195PCB100111 but i found a match on shopjimmy.com.

You are correct about this being a samsung chassie with the samsung boards and the sanyo main board. the pre power board is also sanyo.

Id have no issues attempting to reflow the solder. how precise does the placement of the flux need to be and a assume you place it on the solder side of the board (not the component side)

[richardjefferson]

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

I tried a couple more pics for clearer view

[tom66]

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

Can you get a higher resolution?

As an aim for quality, try to make it such that I could read the component identifiers (e.g. R393, C823) next to most of the components.

If you have to break the image down into sections and take individual parts.

[richardjefferson]

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

i took more pics in as high a res as my hand held camara would allow. I could zoom in on the first overall pic and see the details but ive also taken a bunch of macro's that ill attatch as well. im not sure what you will be able to see.

[richardjefferson]

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

second set of pics

[richardjefferson]

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

last set of pics. i know there is some overlap in these. i deleted a lot that had too much glair or were fuzzy. hopefully these will be clear when you try to down load them.
let me know if you need different ones.

[tom66]

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

Those pictures are much better than what we normally see here, thanks.

My guess, as everything on the top side is reliable QFP (I've never, ever seen a QFP package have a soldering failure), that the failure could be inside that metal can, as it is shield to reduce radio interference (high speed video produces a lot of that!) Do the screws allow you to easily remove it?

[richardjefferson]

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

I should have looked more closely before i took those screws out. They are
holding something to the top of the inside of that cover. What ever it was rotated when i started to take off the 2nd screw. I put the screws back in, hopefully nothing was damaged but there was much resistance so i think im ok.

upon closer inspection, the cover is soldered in 3 places (three sides) on the component side of the board.

On the back side there are 9 (nine) solder points.

Im game to desolder this if you direct me to. At the component level ive only replaced a couple of CAP's so my soldering skills are not very good and i might need to pick up a better solder sucker (im using a rubber ball sucker).

Pics attached of all solder points

[tom66]

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

Attempting to desolder that would probably lead to damage to the board. Don't try it yet. I would guess the screws hold in a heatsink. Whatever is under there must get quite hot.

You can try a reflow but I do not think it will work with that shield on. I do not yet know for certain it is the main board. You can try tapping on the board while the TV is running. If it cuts out or shows video distortion, that could be a clue. But it's damn annoying that the shield there is soldered on!

[richardjefferson]

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

what is the procedure for a reflow?
i need to pick up liquid flux, do i "paint" the back of the board with that then heat it up or just try and get it on certain connection pins?

[richardjefferson]

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

stamped into the top cover is the following:
19-N4TE 1AA2SHFO744--

stapmed into the bottom cover is the following
19-N4TE 1AA2SHF0743--

that did not bring up any results on google search thought

CORRECTION. its comming up as the identifier for the main board on a couple of part sites.
i thought perhaps it could identify the component underneatn

[tom66]

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

Problem with that shield on there you can't get the flux under the chip.
You -can- do a reflow without it, but it won't work half as well as one with it.

[richardjefferson]

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

i put the main board back in and turned the tv on. first time i turned it on, i tapped on the boards heat sinc and the cover , didnt seem to make any difference in the pic. tv shut down in under a min. I had forgotten to plug in the speaker connector. second time i turned it on and tapped on the board again enough to shake it. no change to picture. that was about half hour ago and its still on. would be nice if symptoms were consistent.

[tom66]

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

You can potentially use a hair dryer to heat it up ... if it starts going wrong you found the faulty area.

[richardjefferson]

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

It was on for last 12 hours. i had propped it up against the wall but was upside down. i turned it off and rotated it so that is right side up leaning against the wall. after i rotated it right side up and turned it back on, it stayed on for about 5 min, shut off and then turned itself back on. its been on now for about 6 hours. Ill give the hair dryer a try to see if it will shut off.
I know if i hang it back up on the wall, it will shut down! LOL

[richardjefferson]

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

Update - there is no consistency with the behavior of this unit. After my last post, it stayed on for 48 hours in an upright position with out a problem. i decided to turn if off and move it around to start introducing heat on the various components. its been unpredictable since that move. have not gotten to the heat yet. It powered itself back on a couple of times after shutting down. sometimes it will turn off but not let me cycle it back on for an hour or so, will stay on sometimes for a few min, others for a few seconds. i have it laying flat now. and trying to see if tapping on the board heatsincs have any effect on making the tv power on or off.

i never asked about the board under the main board. ive attached pics of the board in place. there are 3 led's on that board. when the tv is on, 2 stay lite and 1 blinks.

What role does this board play?
ill update this thread after more experimentation

[tom66]

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

That board is the control board.

It generates the signals which control the plasma panel through the sustain boards and the column drivers.

The blinking light indicates the board software is running (it uses a microprocessor), and the other two LEDs usually indicate a binary or linear temperature scale. All four lit might be a problem, two lit is fine.