Samsung-LE32B530P7W-Intermittant Back Light

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

After spending more time in trying to solve this backlight issue without sucess, I decided to take a chance and purchase another PSU from LCD TV Parts at a cost of £25.00 (free shipping) Since replacing the PSU on Friday morning, the TV has been working 100%

It would have been nice to have found the fault on the PSU then just replace it. Just seems I've not gained any experience in just changing a PSU.

Thanks again everyone for your help.

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Nothing touching other lead? Maybe cold joint under this IC and pressing it fixes it temporarily.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I'm not to sure if it is the transformer! There is a Programmable Shunt Regulator - KA431AZ (ICP802) next to the transformer (TI801S). At first glance I thought is was a transistor of some kind so I started to probe it with my DVOM set on AC. When I touched the first pin on the left, the backlights turned on and my DVOM read 127.6VAC. Removed the red probe and the backlights stayed on for around 15s. Tried various times and same thing happens every time. I now have the wiring diagram and trying to figure out how the backlights come on using my DVOM?

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Cant find any info on that transformer tho you can buy one in Oz for 4$ish- perhaps
test the voltage on the primary side but have meter on 600v or higher if you have it.

Perhaps see if you can follow where that pin 23 invonoff goes to? - on both boards.

Could of course still be a duff cap somewhere -they look to be mainly Sam Young?
@Tom66 If the lower voltages "wobbled" might it be enough to switch on a protection
that closed the lamps down

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Retouch all joints on power components. Anywhere that looks like it gets hot or gets hot when running (test with TV off of course!)

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Checked the board for cold solder joints, tried the hairdryer trick, don't have an freeze spray or compressed air.

What kind of coil readings would I expect to find on T1801S? The number on it is QGAH02092 SW
SW-02B 09 OSC.

I have 002.2R across the two upper pins which I believe to be the secondary windings (correct me if I'm wrong) and 000.9R on the two lower pins.

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

The more times I turn on this TV, the backlights will fail to come and I have to leave it for some considerable time to re-test. I may leave it overnight and try again in the morning.

That is an important observation - possible sign of cold joint as Tom says.
Tomorrow perhaps try the hairdryer and or freeze spray/compressed air test.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Will do!

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Cold solder joint? Retouch all joints on the board that look suspect.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

The more times I turn on this TV, the backlights will fail to come and I have to leave it for some considerable time to re-test. I may leave it overnight and try again in the morning.

Had a quick look at retiredcaps guide, lot of reading to catch up with.

Thanks,

Later.

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I like it! What we are trying to do is to get one lamp to light/flash at a time
( It is often difficult to tell if there is a fault when they all flash on at once )so using your wires can you light each bulb in turn. I am not sure if there are going to be 8 bulbs or 4 "U" bulbs. If you can do that, as I said before try and observe the "colour " of the flash - pinkish suggests a bulb is failing.
As you say I know it doesnt really seem necessary as the set is know to work then stop, but it is a matter of eliminating as many known reasons for 2 seconds to black as possible and these are normally the easy tests!!

I dont recall, and it is easier for me just to ask than skim back through but have you read this guide by retiredcaps - it will help if it comes down to component testing - start at post 19 - its not as long as it looks.
https://www.badcaps.net/forum/showthread.php?t=10419

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I'll check that fuse shortly.

Not sure how well you can see the photo but, the PSU has now parted company with the backlight connector. I've inserted 8 spade connectors into the black vertical connector which hold the tubes. On each one of these connectors I have a wire link which enables me to join the PSU to the black connector in any combination. So far I've tried all kinds of combinations but the backlight has always turned off after a few seconds.

The weird thing with this TV is, it can work for days and then all of a sudden, the backlights fail?

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Yes - I see that now thanks - please see late edit post 21 re tcon fuse

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

You beat me to it!

I tried lifting the black connector but, only comes up a small amount because the tubes are holding on to it from inside the panel.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

The 8 flat tabs on the PSU slot into the 8 square holes on the long black vertical connector.

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

No I dont think there are - makes sense now see attached internet picture of
this board.



EDIT just as an afterthought there is a white fuse on the Tcon have you tested it.
cant see it affecting the BL problem but see a fuse and test it is what I think.

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Fuse o.k. 000.2R. Voltage across big cap when just plugged in is 326.2V. Switch on TV, voltage rises to 344.2V.

I've tried lifting the long black connector that fits onto the lamps inside the panel but have a feeling they might break if I'm unable to hold them. Hope this makes sense?

1 First voltage is ok - second may be a bit on the low side.

2 Probably does make sense - but doesnt mean anything to me - perhaps Tom or the others have seen something similar.

Not sure where to go next are there no wires between the power/inverter board and the lamps, that you can unplug?

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Fuse o.k. 000.2R. Voltage across big cap when just plugged in is 326.2V. Switch on TV, voltage rises to 344.2V.

I've tried lifting the long black connector that fits onto the lamps inside the panel but have a feeling they might break if I'm unable to hold them. Hope this makes sense?

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I don't have any spare ccfl bulbs. I do have another Sammy but can't use it for spares as I've just repaired it.

If you can get to the lamp connectors you can do the one at a time flash for each bulb. Disconnect all but one and see if it flashes and try and guage if they all flash the same brightness and colour.

Can you also check the fuse next to the Big Cap and the voltage across the Big cap when it is just plugged in and when you have pressed the power button

High voltages for these tests when doing the lamps un plug from mains and let it stand for 5 minutes between each test. 600-800Vac

Big Cap test could be 400VDC

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I don't have any spare ccfl bulbs. I do have another Sammy but can't use it for spares as I've just repaired it.