Samsung-LE32B530P7W-Intermittant Back Light

[AlbertRoss]

Hi All,

Purchased this Sammy as a spares or repair. Previous owners said it would work fine for around two to three days and then the screen would go blank but sound is still there. No matter how many times it was turned on, the screen would still be blank. Leave it for a few days and it returned to normal.

Anyway, It all came to life when I fired it up with no problems, perfect picture, sound, everything ok for a few days until now. It turns on, has sound but no back light, changes channels ok either on the set or by remote. Performed various 'wiggle' tests here and there thinking it's a loose connection or something but, no luck.

I'm stuck now where to check next as I'm not sure what powers up the back light?

[randtek]

Re: Samsung-LE32B530P7W-Intermittant Back Light

An easy check is to unplug the TV, disconnect the cable going from the main to the power board. then plug the TV back in.; The backlights should come on and stay on with that plug disconnected. This will confirm or eliminate the main board as the source of the problem.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Disconnected cable going from main to power board, turned TV on, backlights stayed on for approx,. 15s and then turned off. Tried it with cable connected, does same thing but now I have sound. What actually operates the backlights?

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

When it is on with a source and the sound is on can you see a very dark image on the panel - sometimes shining a torch onto it at various angles can help.

Next You will have to try and get to the Tcon. The Tcon will be under that middle panel where the orangyred flat cable goes. In fact you should try and remove clean and reseat it , then try the tv again.

Looks like the inverter transformers are on the power supply but cant see the plugs for the lights - can you take the power board off and do a picture of the underside there may even be another board under it?

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I can see a very dark image moving around on the screen when using a flash light. Have removed the T-Con board, connectors look ok, although I don't have any special cleaner. Removed the PSU, no more boards underneath it.

Re-installed components, turned on TV, back lights went off at around 60s.

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Closer pic of here if possible please.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Is this o.k?

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Perfect picture, I wish all pics on this forum were like that.

OK pin 23 is your on/off pin. Can you check this with PSU installed? Is it stable or switching off when the backlight goes off?

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

When back light on, pin 23 reads 2.12V stable. When back light turns off, same reading. I'm checking this with the PSU cable to main board disconnected.

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

I am pretty sure it needs to be connected up



Still couldnt see the lamp connectors is it hard to get the board off that frame at the bottom.

Inverter transformers look a bit different to ordinary Darfons. I have marked what I think are relevant pins on attached.
Meter on Ohms 200 or 20 if you have it measure P1 >P2 then meter on ohms
2000 test S1>S2 and S3>S4. Then repeat on other transformer.
Post results as
T1
P1>P2 = xx ohms
S1>S2 = xxxx ohms and so on

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Regarding your previous question, I re-connected cables and checked voltage on pin 23. This time I had 4.46V stable with backlight on or off.

Now I'll get back to the remaining question.

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Ok,

T1 (T1801)
P1>P2 = 009.1R
S1>S2 = 0.833K
S3>S4 = 0.836K

T2 (T1802)
P1>P2 = 009.1R
S1>S2 = 0.836K
S3>S4 = 0.836K

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

So main board isn't shutting backlight off. Check 13V pin on board.

Odd design. Looks like the big transformer on the board drives the other two transformers. Is there a part # such as BN44-xxxxxx that could be used to get schematics?

[tom66]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Never mind. 'twas staring me in the face. Schematic:
http://www.tgohome.com/ServiceManual...g_BN44-00261B_[SCH].pdf

[selldoor]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Ok,

T1 (T1801)
P1>P2 = 009.1R
S1>S2 = 0.833K
S3>S4 = 0.836K

T2 (T1802)
P1>P2 = 009.1R
S1>S2 = 0.836K
S3>S4 = 0.836K

Both look good individually and relative to each other.

Do you have any spare ccfl bulbs old panel/laptop screen etc

[AlbertRoss]

Re: Samsung-LE32B530P7W-Intermittant Back Light

Pin 21 = 12.75V. Pin 22 is also a 13V ref, this reads 12.75V.

[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.

[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

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

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?