Samsung LN40B500P3F has Standby light, doesn't turn on.

[checkport88]

I'm trying to fix this Samsung LN40B500P3F LED TV for my grandpa. I suspect that there are problems with the main board based on reading old threads. I'm hoping that somebody still has a service manual for this.

Backlight comes on when I remove the ribbon cable from the power supply board. I basically want to narrow down the problem so I can decide if I need to replace a board or try to fix it.

[dick_barton]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Generally if the backlights come on when you disconnect the power supply from the mainboard it tends to be that the required signal from the mainboard is missing.

Can you post sharp focused pictures of the circuit boards. Add them to the post using the "Go Advanced" button.

Have you taken any voltage readings at the power supply connector to the mainboard?

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Hopefully those photos come through.

I haven't measured any voltages yet, I'm not really sure where to start. Thanks.

[dick_barton]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Does the set react to the remote control. Do you have sound?

If you can give the pin number, name and voltage read at the connector in the red box to see if there are any voltages missing.

Pin 1 Name Voltage
Pin 2 Name Voltage
.
.
.
Pin 30 Name Voltage

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Here are the voltage readings and a close photo of the pinout. Let me know if you see something that looks wrong.

Sadly, I don't have the remote control for this TV. I used a Fire stick in the hdmi to check for audio but didn't get anything.

[dick_barton]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Just out of curiosity what voltage do you have at the fuse (both sides) of the Tcon, if this is your tcon board when you switch on the set.

When the mainboard is disconnected from the power supply the backlights come on so can you measure the voltage at Pin 23 (Inverter On/Off)

[nomoresonys]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Not exactly sure but I'm thinking that this board will work, many of these boards are interchangeable: https://www.ebay.com/itm/Samsung-LN4...sAAOSwZIxe3Wu1

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

I wasn't able to access the T Con board because it is behind a rivetted enclusure, see attached. Unless I'm missing something.

I have attached the voltage readings with all boards plugged in and AC power plugged in, measured from the back of the board. First with power off, then when I pushed the power button. None of the voltages changed when I pushed the power button.

Let me know if your see anything interesting.

[MrMagoo]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

The Tcon is under that steel cover. You will have to lie the tv screen side down on a large flat surface (kitchen tables are good). Undo the screws that hold the stand and the bracket. with that out of the way you should see four Philips head screws that need to undone. lift the steel cover off the tcon and you should be able to check fuse. If not sure you might want to post picture of the tcon as well.
Cheers

[neilc6]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Yes likely a bad main board. I have used a 40" main board on a 46" B series.

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

I measured across the TCON fuse while pushing power button, but it measured 0V. Photo of the TCON board attached.

I measured PIN23 on the power board, with the main board disconnected, AC plugged in, backlight on... It measured 2.13V.

I guess I'll start looking for a replacement for the main board? Some good suggestions on this thread earlier.

Let me know if there's anything else I should check.

[budm]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

"I measured across the TCON fuse while pushing power button, but it measured 0V. Photo of the TCON board attached."
That is not how you check to find out if you have Voltage feeding the T-con board or not and if the fuse is good or not, You test the Voltage of each end of fuse with ref. to circuit ground, in this case, the chassis.
You use Ohm mode to check and see if it shows as a short if it is good, infinite resistance if it is blown open, and of course no power applied when testing resistance.

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

You're right, oops I should know better than that. Anyway, I measured the voltage on each side of the TCON fuse with respect to the chassis. It was always at about 0.21V or 0.19V each time I tried, and didn't change when I pushed the power button.

Resistance across the TCON fuse was 0.3 Ohms.

[dick_barton]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

This makes me suspicious that you do indeed have a faulty mainboard. When connected with the power supply the backlights fail to come on (knowing that they work) and it looks as though the tcon supply also fails to be switched on. Tcon fuse is OK.

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Are you guys generally pretty confident in ordering an alternate main board, like some of the ones listed above? Or should I stick to the exact model main board for this TV?

[tvtimmy]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Shopjimmy shows 2 mainboards that will work for you.

[nomoresonys]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

Are you guys generally pretty confident in ordering an alternate main board, like some of the ones listed above? Or should I stick to the exact model main board for this TV?

Well 4 highly regarded members and me think it's a mainboard issue...what the hell give it a try.

[checkport88]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

I agree, just a couple guys suggested maybe getting a main board that was from a different model, but that is likely to be compatible. Is that something that is widely accepted or is that kind of risky?

[tvtimmy]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

There may be different models that will give a picture, but the back of the tv wont fit. Inputs are in different places and such, you would have to butcher the back of the tv.
Check with shopjimmy and find a cheap one on ebay.

[nomoresonys]

Re: Samsung LN40B500P3F has Standby light, doesn't turn on.

I don't deal with lots of samsungs but I think it was bruce or nick that said a lot of the sammy boards interchange.