Samsung HL67A750 DLP with bad caps!

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

so... not good. I got the caps today, replaced them tonight. Put everything back together, turn on the TV.... same problem. It starts to come up, I see the input very briefly, it flickers and goes black. switch back and forth between inputs and it keeps doing it. Input 1 and 3 seem to stay up, 2 keeps going out (which is where my satellite is connected). After some struggling, it tries to reset itself. 3 tries to reset, back to the 3 flashing lights. So now I'm guessing the LED Driver? Anyone have any ideas? I think I'm going to go be sick now.

[Caleb]

Re: Samsung HL67A750 DLP with bad caps!

probably time for more pictures, front and back of the boards. Maybe we can see something else. Its not inconceivable that the ripple blowing by those caps damaged something else.

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

I'll have to wait until tomorrow night, so I can put the TV up on my kitchen table to have more room to work on it. The one thing I did check tonight was the 16v lines coming off of that board, they run to the LED Driver board. The board in question is the "P-SMPS" or Sub SMPS, BN96-01726B. When the TV first turns on, the relay clicks, and those lines all jump up to 16V, but they start to fade down from there. The system is designed to recycle itself after approximately 20-30 seconds if the light engine hasn't fired, and the voltage on those 16V lines drops to ~12V before it cycles. when it cycles, the relay clicks, the voltage jumps back to 16 and starts to trickle again, Repeat until it goes into the "three flashing" scenario (which is expected with that connected removed, the LEDs are never supplied power), at which point the voltage just keeps dropping slowly. Thanks for everyone's help on this and my LCD issue, I'm going to take a quick look at that one and see if I can find that EEPROM now....

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

Maybe we can see something else. Its not inconceivable that the ripple blowing by those caps damaged something else.

I think you'll find you only need to see the front of this board, to answer that question...


Here I was, light engine and SMPS pulled out and sitting on my entertainment center, multimeter in hand, testing this and that... I finally finish putting together notes to type up, I pick the light engine up to reconnect a cable.. and I hear a rattling. and somehow, I just knew where it was coming from lol. I pulled the LED driver out and open up the casing around it, and that little black piece dropped out. I know it wasn't something I damaged, so my only guess is that when those caps went, they must have blown that off the board somehow. Someone tell me if that assumption is wrong. More info below.

The one other thing I noticed, that may or may not have any bearing on this... there is a little green LED on the mainboard... when the system is trying to power up, I could see that light flashing, and hear a clicking sound comign from the mainboard/main power supply area. with power to the DMD board plugged in, it only tries for a second or two to power up, then cycled off for a few, relay clicks, tries to come on for a couple of seconds, cycles off, until it has tried three times to come on. With the power to the DMD unplugged, it tries for 30 seconds or longer to come on. I tried to read the 12V lines on that connector, but they fluctuated so wildly, in time with the light on the board flashing, that I couldn't tell you any one solid reading. I also tried reading the 12V and 5V lines from the DMD to the LED Driver, and saw similar issues. At the same time, while that light was flashing, the output to the P-SMPS was a steady 336V,when it cycled off, it would drop down to 300V. Also, as long as that light was flashing, the output from the P-SMPS was a steady 16V on all three lines.

Ignore the error when opening the PDF, I chopped relevant pages out of the full Service Manual, because it was too large to post here (13 MB). Here's the real question - do I make the assumption that the issue with the LED Driver board was a result of those bad caps? Or do I still have something else wrong? I know I have to at least replace that board, which is going to be ~$70 if I buy the *one* used one I can find online. What if that's not the only problem? Then I'm looking at potentially either the Main Power Supply, the Mainboard, the DMD board, or some combination of the above.

This would seem to be the LED Driver board, but this also seems correct. Both have the same board (bp41-00317c) but the other number differs between the two (BP94-02327A on the first link, BP97-01284C on the second), and not one of those 3 numbers is listed in the service manual.

[ben7]

Re: Samsung HL67A750 DLP with bad caps!

I think you'll find you only need to see the front of this board, to answer that question...


Here I was, light engine and SMPS pulled out and sitting on my entertainment center, multimeter in hand, testing this and that... I finally finish putting together notes to type up, I pick the light engine up to reconnect a cable.. and I hear a rattling. and somehow, I just knew where it was coming from lol. I pulled the LED driver out and open up the casing around it, and that little black piece dropped out. I know it wasn't something I damaged, so my only guess is that when those caps went, they must have blown that off the board somehow. Someone tell me if that assumption is wrong. More info below.

The one other thing I noticed, that may or may not have any bearing on this... there is a little green LED on the mainboard... when the system is trying to power up, I could see that light flashing, and hear a clicking sound comign from the mainboard/main power supply area. with power to the DMD board plugged in, it only tries for a second or two to power up, then cycled off for a few, relay clicks, tries to come on for a couple of seconds, cycles off, until it has tried three times to come on. With the power to the DMD unplugged, it tries for 30 seconds or longer to come on. I tried to read the 12V lines on that connector, but they fluctuated so wildly, in time with the light on the board flashing, that I couldn't tell you any one solid reading. I also tried reading the 12V and 5V lines from the DMD to the LED Driver, and saw similar issues. At the same time, while that light was flashing, the output to the P-SMPS was a steady 336V,when it cycled off, it would drop down to 300V. Also, as long as that light was flashing, the output from the P-SMPS was a steady 16V on all three lines.

Ignore the error when opening the PDF, I chopped relevant pages out of the full Service Manual, because it was too large to post here (13 MB). Here's the real question - do I make the assumption that the issue with the LED Driver board was a result of those bad caps? Or do I still have something else wrong? I know I have to at least replace that board, which is going to be ~$70 if I buy the *one* used one I can find online. What if that's not the only problem? Then I'm looking at potentially either the Main Power Supply, the Mainboard, the DMD board, or some combination of the above.

This would seem to be the LED Driver board, but this also seems correct. Both have the same board (bp41-00317c) but the other number differs between the two (BP94-02327A on the first link, BP97-01284C on the second), and not one of those 3 numbers is listed in the service manual.

Solder that component back on and see what happens. It looks like an inductor to me. The solder on it might have cracked, causing it to fall off. When it was rattling around inside there, it could have been shorting something out, causing the cycling power problem.

[tom66]

Re: Samsung HL67A750 DLP with bad caps!

Or the LED light engine may have detected a fault preventing the set from powering up.

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

Solder that component back on and see what happens. It looks like an inductor to me. The solder on it might have cracked, causing it to fall off. When it was rattling around inside there, it could have been shorting something out, causing the cycling power problem.

Well, it wouldn't really have been rattling around until I moved the light engine, but there is a "daughter board" of sorts that sits underneath it that it might have landed on. I'm nervous about soldering that back on, because it's such a small spot, and I get shaky when I get nervous What are the chances that something like that would simply fall off the board? the only experience I have with components spontaneously removing themselves from a circuit has been when a cap, diode, or resistor actually fails, and blows itself up, but this would be a first for me. If you guys think it's safe, I could certainly try though!

Or the LED light engine may have detected a fault preventing the set from powering up.

Tom, the service manual says the following:
"Protect Status
1. Attempting to turn the LED ASSY on fails repeatedly
If turning the LED on fails, the set automatically tries turning the LED ASSY on 3 times. If all attempts fail, all LED's on the front panel will blink. Check the LED ASSY, LED Driver and the Sub power or SMPS and replace them if necessary"

So while it doesn't specifically detect a fault in that board, it detects a general failure to light the engine and goes into that fault state.

The full Service Manual is over 13 MB, do you know anywhere it could be hosted for easier access if anyone else wants it?

[tom66]

Re: Samsung HL67A750 DLP with bad caps!

I can host it on toms-service-manuals.com. PM me and you can send it to my email address.

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

PM sent! Do you agree I should try to solder that inductor back on and see what happens?

[tom66]

Re: Samsung HL67A750 DLP with bad caps!

Yep, definitely. It's definitely not going to work without it. Do you remember seeing any flash of image before?

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

oh yeah, it was working for the longest time, despite having some startup issues. it would take some constant retries and would finally start. Then the last time it was up and running, my 17 month old hit the power button, and that was all she wrote. It tried to come on after I replaced the caps on the SMPS, but it just wouldn't STAY on, and it stopped doing even that. Any tips on how to solder that back on solidly? I've never done any SMD soldering like that before...

[tom66]

Re: Samsung HL67A750 DLP with bad caps!

Simply use a pair of tweezes to put it on the board steady, then solder to each end. Are the pads exposed? If you have difficulty holding it steady, it may be a good idea to use a dab of glue to hold it on the PCB. Don't use glue on the solder pads though-- do it on the bare board.

[tom66]

Re: Samsung HL67A750 DLP with bad caps!

SM: http://www.toms-service-manuals.com/...&Search=Submit

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

So, I used the glue suggestion last night, and did the best that I could to re-solder that inductor. tested continuity between the pad and the side of the conductor, it was good. Reinstalled in the TV, and HOLY CRAP IT TURNED ON. once. when I buttoned it back up and moved it back to my entertainment center it was just as dead as before. During one of its attempts to cycle on, I heard a faint fizzle sound from inside the TV, like a component letting the smoke out. TV has the exact same symptoms that it had before now. Going to pull it apart again tonight and check it out, see if it was just my solder joint burning up (admittedly, it was not by best work!).

But for one glorious minute, the TV was in good shape.

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

No time to do anything today, as we were getting ready for my wife to go into surgery tomorrow. I was reading through a thread over on AVSForum though, and someone had said something that sparked my brain... I noticed when i removed the LED Driver from the metal casing, the back side of the board appeared wet, as did the rubber seal that some of the components sat against. I felt the liquid, it was a kind of greasy/sticky feeling, unfortunately I couldn't smell anything. Someone had said it was possible the caps on that board leaked, and I'm wondering at this point if I am better off just replacing the board that continuing to try to troubleshoot it. $65 for a replacement online. Thoughts? See the second cap from the left in this pic, C9314 for an example of the fluid that was on the back. and yes, I've blown all the dust off since I took this picture!

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

Well, it took just over two weeks, but I finally got the new LED Driver in today. Pulled the TV apart, replaced the board, put it all back together and.... same thing. TV tries to turn on, cycles three times, and goes into the 3 flashing light mode. So at some point this weekend, I'm going to have to take the time to pull it all apart again, and check the motherboard and main PSU. If both of those check out, that's going to mean it's the DMD board (I just replaced the chip less than 12 months ago) and that's going to mean selling this thing for parts.

[agentrnge]

Re: Samsung HL67A750 DLP with bad caps!

Tiezane,

I think I have a bad LED driver as well on a HL61A750. Will be pulling it out tonight to inspect. I had a blue LED fail. Replaced with a used LED. That failed after 4 months. Verified LED was bad, assumed it was just bad luck. New LED in, TV does not complete power up. Triple LED flash upfront, along with the faint smell of smoke being released :\. voltage was the same from the driver to each LED. Blue LED is disconnected now and otherwise known to be working ( if driven by green channel or a 9v battery ).

I can only find 2 driver boards available for $160+ blek. I haven't checked further up the chain to see if its the DMD/main. Doubting that is the case as the TV works fine with the blue LED out of the equation. I had no power up issues like you did.

So 1) curious how you made out checking out the DMD/motherboard/main PSU.
2) If the TV is toast and being parted, would you be selling the newer LED driver?

[Tiezane]

Re: Samsung HL67A750 DLP with bad caps!

So 1) curious how you made out checking out the DMD/motherboard/main PSU.
2) If the TV is toast and being parted, would you be selling the newer LED driver?

1) I'll let you know this weekend
2) If the wife won't let me drop any more money on fixing this thing, and I have to part it out, I think we could come to an arrangement.

[agentrnge]

Re: Samsung HL67A750 DLP with bad caps!

It looks like its almost definitely the driver in this set. Back of the board is visibly darkened across the center of the board. The center/green channel looks like its cooked. , but oddly its been the blue channel that's giving me problems. Its a bit rough looking all over the board on the back. lots of dark spots all over, looks almost like corrosion around 2/3 of solder points. I cant imagine that this is expected to look like this. 7500 hours over ~5 years on the TV.

Front of the card looks OK except for one resistor ( one of the R020s ) on the blue channel has a slightly raised and discolored surface.

Looking forward to see what you find. Good luck this weekend.

[agentrnge]

Re: Samsung HL67A750 DLP with bad caps!

Got the replacement LED driver. This resolved the issue for me. The new part had an additional heatsink attached to all the components that were failed/failing. I'll waste a few minutes on the phone with Samsung and fight it as a known defect/oversight that caused the premature failure.. see if they can hook me up at all.