Samsung UN55KU6300F no standby voltage

[x_orange90_x]

I have no standby indicator light and no light on the optical port. I checked the standby voltage on the two mosfets in the top left and they both read 30mV. I checked the fuse and it has continuity. I also checked the voltage on the two large 450v caps they both read 153v. All of these voltages are the same with and without the main board connected as well as with backlights connected/disconnected.

Nothing looks obvious like a burned ceramic disc cap or bulged electrolytic. No burned resistors, diodes, or anything like that.

[nomoresonys]

Assuming you already unhooked mainboard from powerboard and checked for backlight, check those 4 diodes there on top and the usual easy things to check first, all diodes, resistors on top of board is a good start. And check transistors for shorts between each pin. Finding no problems with any of that, maybe check the caps near the standby transformer.

[x_orange90_x]

Assuming you already unhooked mainboard from powerboard and checked for backlight, check those 4 diodes there on top and the usual easy things to check first, all diodes, resistors on top of board is a good start. And check transistors for shorts between each pin. Finding no problems with any of that, maybe check the caps near the standby transformer.

Correct, I did plug it in with main unhooked.. No backlight. I will need to remove a leg from each diode to check them, correct?

[nomoresonys]

I usually check them in circuit, if they read a little strange then lift a leg.

[x_orange90_x]

I checked those diodes, the transistors, and the caps on that side of the board. The diodes and transistors are okay, the caps aren't shorted, but there's no voltage to anything on the cold side. All of the caps are in the double digit mV with one being -50mV.

I ordered a board from SJ because it was super cheap. They had it listed for $7.20 and I sent an offer for $5 and they accepted it. I'm going away next Friday for 3 days so I had to pay $12 for delivery before then so it wouldn't be sitting outside all weekend. It's so cheap that it was worth it in this case lol. I love that you can make offers right on their website. So far they've never refused one I sent! They had 40 of these in stock.

I did test the backlights and make sure the screen was okay as well, which it is.

[nomoresonys]

Thats great, can't beat that price, nice to see they are accepting offers.

[tw2005]

Been forever since I've touched a TV but coincidentally same power board different Model here in AU. UA55MU6100

it has no standby LED in standby not sure if it's an option in the settings, blinks with remote then failed with a 1 blink.

Disconnect mainboard, no backlight

Diodes D9001, D9002 in parallel, pair shorted , one was dead, other ok. MUR480 800V 4A

Replaced diodes, TV powered on lasted about 15 mins. Same diodes failed, Noticed where one leg of diode was touching the plastic insulation sheet it had melted.

Replaced diodes and C9001 , 201K 1Kv (200pF) TV has been good since.

PSU BN44-00807A

2017 build