2008 Samsung HL61A750 LED DLP owners thread and FAQ - Page 536 - AVS Forum | Home Theater Discussions And Reviews
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Old 08-24-2015, 04:00 PM
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Quote:
Originally Posted by SeekingNirvana View Post
....so these could very well be bad then. Can they still function bulged?
Doubtful they can function normally. The capacitance falls way below the rated value, and the internal impedance goes way up.

Augerhandle has a good eye, to spot the bulges. I didn't even notice it, even though its obvious. Those caps should definitely be replaced.
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Old 08-24-2015, 05:28 PM
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I had just enough time to take a voltage reading of the main smps. I took the reading with the terminal still connected, and at the sub smps. When the TV first tried to turn on, I got a reading of around 220v and shortly after it settled to about 216v and was steady until the next cycle, and went to 220v again.

I did not see a Vdc button on my DMM, but after pushing the Orange button it went into a mode where there is a solid line, and under that line is a dashed line. With this setting I got a reading of 220v. Before I pushed the Orange button it had a symbol that looked like a horizontal squiggly line, and with that I was getting readings like.....0.956. Am I doing it right?

Oh btw after looking at the caps more closely, the bottom of the 4 actually looks split at the cross section. And I found a bigger cap on the sub smps that looks bulging. It's not in the picture, and I'm mobile right now and can't post a new one.

I'll try to get some readings off the 16v wires later this evening.
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Old 08-24-2015, 08:07 PM
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Quote:
Originally Posted by SeekingNirvana View Post
... I got a reading of around 220v and shortly after it settled to about 216v and was steady until the next cycle, and went to 220v again.
The manual says 220 to 400 VDC, so you are around the low end of the range. Maybe the main smps has some marginal components too. Its best to take readings while the boards are connected, to provide the normal loading.
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... it went into a mode where there is a solid line, and under that line is a dashed line.
That is what you want, not the squiggly line.

BTW, I took a quick look, and found a few sites that have the sub smps in stock for around $55, just sayin', so it might be easier than doing cap replacement, assuming the 16V output of your board is bad.

Last edited by cosmicvoid; 08-24-2015 at 08:17 PM.
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Old 08-24-2015, 10:40 PM
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Quote:
Originally Posted by cosmicvoid View Post
The manual says 220 to 400 VDC, so you are around the low end of the range. Maybe the main smps has some marginal components too. Its best to take readings while the boards are connected, to provide the normal loading.That is what you want, not the squiggly line.

BTW, I took a quick look, and found a few sites that have the sub smps in stock for around $55, just sayin', so it might be easier than doing cap replacement, assuming the 16V output of your board is bad.
I got 0v on the 16v output. I poked the probes into the top of the terminal while it was still plugged in and tried 1&2, 3&4, and 5&6 and none of them had any voltage. The black probe went to ground, and red went to the 16v wire. I did not try different combinations like 1&6, not sure if this will matter though. I had the probes in place from the TV being off, and then turned on. It read 0 the entire time.

So would that be the sub smps or the LED driver board? Any other tests to confirm what we think it is?

Edit: never mind that was a dump question.....I am not getting 16v output from the board, so clearly it is bad.

Last edited by SeekingNirvana; 08-25-2015 at 10:04 AM.
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Old 08-24-2015, 11:05 PM
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Quote:
Originally Posted by SeekingNirvana View Post
Makes sense.....so these could very well be bad then. Can they still function bulged? Or when they get like this they can go at anytime?

Guess the best way to answer my question, is for me to take some voltage readings.
@cosmicvoid gave good advice:

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Originally Posted by cosmicvoid View Post
Three blinking indicator leds means there is an LED problem.
Three things come to mind as reasons, in order of likelyhood:

1. the main smps (on top of the main board housing) is not outputting 300 VDC to the sub smps. That voltage runs over the blue/brown wire pair, across the back of the TV chassis. You could try measuring across those two wires, at the connector on either end, while the set is cycling. If the 300V is soft (folds back to some voltage less than 200VDC, I'd suspect the electrolytic caps on the main smps.

2. the sub smps (mounted vertically on the right side, as seen from rear) is failing to output 16VDC to the LED driver module (assuming the 300VDC is in the range of 220-400 volts). You can try to measure 16 v on the 7 wire connector, the wires alternate gnd-16v-gnd-16v etc.

3. the LED driver is not good, either a 16V problem or a digital command problem.

See if you can gather any more data to narrow the search. You can probably push the voltmeter probes into the top of the white nylon connector shells, to touch the upper part of the metal pins.

BTW, you say "cycle 3 times and then just go black". I assume you're referring to the screen. What is it before it "goes black"?

"The wise understand by themselves; fools follow the reports of others"-Tibetan Proverb
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Old 08-25-2015, 07:43 PM
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Quote:
Originally Posted by Augerhandle View Post
The tops of the bottom three caps in this pic appear to be bulging...
Good catch Augie!
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Old 08-25-2015, 10:15 PM
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Quote:
Originally Posted by SeekingNirvana View Post
I got 0v on the 16v output. ... I had the probes in place from the TV being off, and then turned on. It read 0 the entire time.
Just to double check, are you sure the DMM probes were touching the metal pins in the connector?
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So would that be the sub smps or the LED driver board? Any other tests to confirm what we think it is?
At this point the LED driver is not a prime suspect; usually driver will fail on 1 or 2 color channels, rarely all 3 at once. One other thing to check: on the sub smps board, just left of where the brown/blue wires plug in, is a white ceramic fuse. With the wires disconnected from the sub smps, set your DMM to ohms (the omega symbol) and measure across the fuse terminals. You should get near 0 ohms. If you get a high (infinity) ohms reading, the fuse is blown.
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Edit: never mind that was a dump question.....I am not getting 16v output from the board, so clearly it is bad.
Yes, its bad, even if only for the bulging caps. Do you plan to replace it, or try to repair it. The repair route is marginally cheaper, but a hassle to perform.
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Old 08-26-2015, 11:41 AM
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Quote:
Originally Posted by cosmicvoid View Post
Just to double check, are you sure the DMM probes were touching the metal pins in the connector?At this point the LED driver is not a prime suspect; usually driver will fail on 1 or 2 color channels, rarely all 3 at once. One other thing to check: on the sub smps board, just left of where the brown/blue wires plug in, is a white ceramic fuse. With the wires disconnected from the sub smps, set your DMM to ohms (the omega symbol) and measure across the fuse terminals. You should get near 0 ohms. If you get a high (infinity) ohms reading, the fuse is blown.Yes, its bad, even if only for the bulging caps. Do you plan to replace it, or try to repair it. The repair route is marginally cheaper, but a hassle to perform.
I'm pretty sure the probes were touching the metal pins. I tried on all of the connectors multiple times, and pushed in with good pressure. I can take the connector off and meausre off the pins directly just to be sure though.


I will check the fuse when I get home.

If it does in fact turn out to be bad caps, I'll replace the whole board in lieu of replacing the caps. I'm confident I can do the work, but since my time is limited I'll go the quicker route, which replacing the board seems to be.
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Old 08-26-2015, 09:45 PM
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If you verify no 16V output, it doesn't much matter what the reason is.
You can find links to sellers by searching Google for "samsung BP96-01726B". Skip the ones higher than mid-$50.

encompassparts.com
ebay.com
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Old 08-31-2015, 07:16 PM
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I fired up my HL61A750 a few minutes ago and everything has a green tint to it So I am assuming my blue LED went out, but how do you know if the led driver is the root of the problem or just a bad LED? It looks like Samsung doesn't offer the LED driver anymore but I think I found a few places that might have it in stock.

Thanks,
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Old 08-31-2015, 09:57 PM
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... everything has a green tint to it So I am assuming my blue LED went out...
That doesn't make sense. If the blue LED died, the screen would have a yellow tint. The only way a green tint would happen is if both the red and blue LEDs died. If the red LED died, the screen would look cyan (blue-green).

You can check each LED separately using the 9V battery method, but you'll have to open up the black plastic shell to get at them.

BTW, once in a great while I get a true "green" tinted screen, but its due to a HDMI handshake error, and it goes back to normal if I unplug/replug that input (just saying its a possibility).

The LEDs are fairly easy to find online. The driver module, not so much.
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Old 09-01-2015, 06:58 AM
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Well maybe it is more yellow, now that I have looked at it again. I'll swap some cables around and make sure it isn't something do with the hdmi although it is doing it across all inputs.

So from what I have read on here my understanding is the LED driver board could cause the led to go bad, is there anyway to tell if the led driver is the problem?

Thanks again,
Devin
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Old 09-01-2015, 07:05 PM
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... my understanding is the LED driver board could cause the led to go bad, is there anyway to tell if the led driver is the problem?
Its not very likely the driver would damage the LED, but I suppose its not impossible. If you disconnect the 2-wire heavy cable (blue/white) and test the LED with a 9V battery, and it lights up, then that pretty much points at the driver being the problem. The best thing to try is swap out the driver module for a known good one. Easier said than done, I know, as the driver is not easy to find online.

Earlier on this thread, someone had a driver problem, where the power inductors were not heatsunk properly, and one channel got hot enough to melt the solder and the inductor fell off the board. That kind of issue would be one way to lose only one color channel. That kind of problem is relatively easy to repair, if you have any electronic skillz.

Regarding the 'battery test' of an LED, it is critical that the polarity is correct, else you may destroy a good LED. This test must be done quickly (short duration), as the LEDs are NOT intended to operate on 9V.
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Old 09-01-2015, 08:41 PM
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Originally Posted by cosmicvoid View Post
Its not very likely the driver would damage the LED, but I suppose its not impossible. If you disconnect the 2-wire heavy cable (blue/white) and test the LED with a 9V battery, and it lights up, then that pretty much points at the driver being the problem. The best thing to try is swap out the driver module for a known good one. Easier said than done, I know, as the driver is not easy to find online.

Earlier on this thread, someone had a driver problem, where the power inductors were not heatsunk properly, and one channel got hot enough to melt the solder and the inductor fell off the board. That kind of issue would be one way to lose only one color channel. That kind of problem is relatively easy to repair, if you have any electronic skillz.

Regarding the 'battery test' of an LED, it is critical that the polarity is correct, else you may destroy a good LED. This test must be done quickly (short duration), as the LEDs are NOT intended to operate on 9V.

Okay, good to know. I haven't opened it up yet, I switched some cables around and took my receiver out of the loop to eliminate any hdmi problems and the problem still persists. I haven't really watched much tv since it happened but tonight I have and it is definitely missing the blue color. Everything that would normally be white is yellow.

Tonight another strange thing happened, the tv shutoff for a few seconds and came back on only showing red. I shut it off turned it back on and I had the green led back. I'm starting to think the problem goes deeper than just the blue led going bad.

Thanks again for the help,
Devin
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Old 09-01-2015, 10:15 PM
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... I'm starting to think the problem goes deeper than just the blue led going bad.
Hmm, maybe so. Now the driver module becomes suspect, but 'no smoking gun'. I can't help but wonder if things have been stressed by overheating; i.e. is there a lot of dust inside that reduces the cooling of the LEDs.

Do you want to spend the time, effort, and $$ to fix it yourself? Or even try to have it fixed by someone else? The LEDs are about $100 per color; the driver about $75-100 if you can find one for sale.
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