Samsung LN32B350F1 no video

[brianr20v]

Hi all I am new to this forum and any assistance would be greatly appreciated. I have a Samsung 32 Ln32B350F1XZP that I have, its not powering up hoping it was bad caps. that was not the case all of the caps look good and all the fuzes are good. I tested the power boards output pins and all tested good except pin12 (inverter on/of) which am getting 5.1vdc when the power strip is off, however when the power strip is on (which is the white strip) I am getting 0vdc. The power light is steady red when its off and blinks when you try to turn on. I thought the problem was the T-CON board which I purchased and changed but that wasn't the problem. Continue doing test on the board at CP815 when the Tv is off I am getting 78vdc and when its on I am getting 257vdc. Can anyone please help? Thank you in advance for all your help.

[budm]

Re: Samsung LN32B350F1 no video

Here is the diagram of the power supply/inverter board.
If you disconnect the white connector on the power board that goes to the main board, when you plug the TV into the outlet, the backlights should turn on, if it does, then the problem is on the main board, if not, then you have problem with the power supply board.

[brianr20v]

Re: Samsung LN32B350F1 no video

If I disconnect the white connector on the power board that goes to the main board, when I plug the TV into the outlet, the backlights does not turn on, it blinks and shuts of sometimes and sometimes it does not blink at all, while I was doing my test on the power supply board I did get the screen to come on and I switched of the unit to see if will come back on and to my luck it didn't.

[budm]

Re: Samsung LN32B350F1 no video

What is blinking? If that connector is disconnected, there will be no power to the main board so the LED on the front of the TV should not show anything.

[brianr20v]

Re: Samsung LN32B350F1 no video

The Backlight will blink once sometimes when I connect back the white connector sometimes.

[budm]

Re: Samsung LN32B350F1 no video

OK, the power supply/inverter board is bad. Did you download the diagram?
Leave the white connector disconnected, check the DC voltage right at the two pin of the main filter cap CP815 (100UF 500V), it should have about 380Vdc on it.
Also check the DC voltage on CN802 as shown in the diagram, use pin 3 as the GROUND ref for the secondary circuit ground, report the readings.

[brianr20v]

Re: Samsung LN32B350F1 no video

when I check those two pins of the mail filter cap am getting between 65-70vdc reference to ground.

[budm]

Re: Samsung LN32B350F1 no video

You have to measure right at the two pins of the cap, you are working in the hot side of the circuit, the ground ref point for the hot side is the negative leg of that filter cap, not the chassis.

[brianr20v]

Re: Samsung LN32B350F1 no video

sorry am getting 314.5vdc

[budm]

Re: Samsung LN32B350F1 no video

OK, that is low.
You need to read these threads:
post 116: https://www.badcaps.net/forum/showth...89b#post319413, Notes: his reading of 340V is also too low, but check the Diode anyway.

https://www.badcaps.net/forum/showth...ht=ln32b360c5d

https://www.badcaps.net/forum/showth...89b#post298560

[brianr20v]

Re: Samsung LN32B350F1 no video

ok read most of those trends so what your saying is that when the connector is disconnected I suppose to read close to 400v so my problem most likely lies with DP805,DP804and DP810?

[brianr20v]

Re: Samsung LN32B350F1 no video

well DP805

[brianr20v]

Re: Samsung LN32B350F1 no video

So i finished test these diodes (out of circuit) DP805, DP804 and DP810 and all seems good,what next?

[tom66]

Re: Samsung LN32B350F1 no video

Do you see capacitor CP809? It'll be somewhere near those diodes you tested I expect. Test the voltage across it.

[brianr20v]

Re: Samsung LN32B350F1 no video

voltage across CP809 is fluctuating between 11.00v and 11.60v.

[tom66]

Re: Samsung LN32B350F1 no video

That is a problem. The minimum for guaranteed startup is 11V, but the maximum is specified at 13V -- so it's more than possible it's not high enough for the IC to start working properly.

Can you check the voltage across CM804 too?

I would suggest you check RM890 for resistance, when the set is unplugged.

[brianr20v]

Re: Samsung LN32B350F1 no video

the voltage across CM804 is 12.5v-13.22v and the resistance across RM890 is4.7ohms.

[tom66]

Re: Samsung LN32B350F1 no video

The turn on voltage for the switching IC is around 18V so it is much too low.
I would recommend the replacement of: CM808, CM804 and CP809 capacitors.

[brianr20v]

Re: Samsung LN32B350F1 no video

ok but will have to do that tomorrow will have to get the caps at the store, Is their any thing I can test again?

[tom66]

Re: Samsung LN32B350F1 no video

You can try and see if some light heat on the capacitors increases the voltage across them -- a hairdryer works well.