Dead Samsung LN46B640R3F

[jcamerox]

I've searched as many posts as I can and still can't find a solution so will do my first post.

TV was bought on Kijij with the only info being it won't turn on. Replaced all the electrolytic caps (except the 2 big ones) in the BN44-00265B power supply and then fired it up. The big caps were 171 v in standby, 387 power on. No picture, no audio, no backlight, did get a melody on start and led went from steady red to green.

Since there was no sound, I decided to replace the main board, and found one on ebay, BN41-01149A. With the new Main board, the led flashes steady at once per second, pushing power on causes the led to flash faster but still no backlight, picture or sound. Also, no melody on start up now and before it seemed to "turn on" with this board the power led just flashes steady.

Here are some pictures with voltage information:

[budm]

Re: Dead Samsung LN46B640R3F

So do you get backlights when the cable between the main board and the power supply board is disconnected? The backlights should be on the minute you plug the AC cord into the outlet.

[jcamerox]

Re: Dead Samsung LN46B640R3F

Thanks for the reply, budm. No backlights obvious to me. Tried it during the night with all the room lights off, plug into 120 V with cable disconnected between ps and main board, no backlights.

[jcamerox]

Re: Dead Samsung LN46B640R3F

Without any suggestions I checked as many voltages as I could on the IC's and such and didn't find anything drastically wrong. A BN 0226A power supply came up on ebay for $30 and bought it as a replacement for the original BN 00265B power supply. As soon as I connected to 120 v with the main board disconnected, the backlights came on. Attached are the voltage readings at the 2 connectors with the backlights on. The BN 0266A looks like a better power supply with beefier transformers and more IC regulators. Problem cured but not solved.