Samsung LN32C450 - Audio but no video

[Aulus]

Hello,

Here's my issue:
The TV turns the front red light on when plugged into AC. When the power is turned on, the TV does it's audio intro, but the backlight is not being powered on. I did the flashlight test and could easily see that the panel was displaying the source.
At this point I had done enough research to hear the #1 reason for this failure to be the inverter board. OK let's order that, but wait I of course screw around some more and found something interesting. When I unplug the main board, the backlight turns on, but the source does not display. The panel not displaying the source makes sense, but why would the backlight turn on when the main board is unplugged? Maybe it still is the inverter board, but I just wanted to make sure before ordering it.

I have visually checked the components and have found none to be showing obvious signs of failure. I did check the PSU to Inverter cable and found pins 10-14 to read ~26V. I did not get a reading for pin 3 (BLU_ON), but I may have read it incorrectly.

Pictures are posted below of most of the components. If you find that another picture is necessary, let me know and I'll upload it. I'll troubleshoot components ASAP when asked (I do work during the day).

Thanks for your help in advance.

[truep]

Re: Samsung LN32C450 - Audio but no video

There is a pull-up resistor on the power board that turns on the backlights when the main is disconnected. Your main board is most likley where your problem lies.

[Aulus]

Re: Samsung LN32C450 - Audio but no video

Cool. That would explain the backlights being turned on when the main is D/Ced.

Do you know a method to test your hypothesis that it's the main board that failed?

[newtothis]

Re: Samsung LN32C450 - Audio but no video

I guarantee its the main board... disconnecting it and getting the back lights shows this. The main isn't sending the signal for BL_ON.

We can check with a DMM if you want further proof?

[JohnnyRockets]

Re: Samsung LN32C450 - Audio but no video

Wow, this sounds (and looks) *exactly* like my TV: LN46C600, another Samsung (surprise surprise).

I did purchase another inverter, which did not help whatsoever, so it is good you did not purchase one and waste your money.

I eagerly await more responses because the resolution to your issue will probably be the same for me.

[newtothis]

Re: Samsung LN32C450 - Audio but no video

Wow, this sounds (and looks) *exactly* like my TV: LN46C600, another Samsung (surprise surprise).

I did purchase another inverter, which did not help whatsoever, so it is good you did not purchase one and waste your money.

I eagerly await more responses because the resolution to your issue will probably be the same for me.

Start a new thread... Post good quality pics of each board and one of entire back of set (so we can see all boards)

[Brass eagle]

Re: Samsung LN32C450 - Audio but no video

I have had issues like this,and my power supply board looked ok,I bought a repair kit of the net and I thought I had ordered the wrong thing as it was a pack of caps,I took them of one by one and replaced them with the new ones,powered it back up,he presto job done,if you can afford to buy a replacement recycled part ,I would recommend you do that

[JohnnyRockets]

Re: Samsung LN32C450 - Audio but no video

Start a new thread... Post good quality pics of each board and one of entire back of set (so we can see all boards)

Can't yet. Waiting for my account to get authorized.

[Edit]: Authorized. Posted a new thread: link.

[newtothis]

Re: Samsung LN32C450 - Audio but no video

I have had issues like this,and my power supply board looked ok,I bought a repair kit of the net and I thought I had ordered the wrong thing as it was a pack of caps,I took them of one by one and replaced them with the new ones,powered it back up,he presto job done,if you can afford to buy a replacement recycled part ,I would recommend you do that

Bad Caps wouldn't allow the back light to come on when the main is D/C, more a case of the Main is not sending the BL_ON signal.

As stated earlier the PSU has a pull up resistor which when the Main is disconnected allows the back lights to come on

[Aulus]

Re: Samsung LN32C450 - Audio but no video

I guarantee its the main board... disconnecting it and getting the back lights shows this. The main isn't sending the signal for BL_ON.

We can check with a DMM if you want further proof?

If it's not too intense I would like to diagnose this with my DMM, not because I don't believe you, but more as a hobbyist looking to learn more about these TVs. Let me know what I need to probe.

[tom66]

Re: Samsung LN32C450 - Audio but no video

So, help us understand: no backlight, but you can still see image, but you DO have backlight when cable disconnected? You might be able to jumper the BL ON/OFF permanently to ON. This might cause the screen to flicker when the set turns on/off or changes sources, but it's not a big deal if you can live with that.

[Aulus]

Re: Samsung LN32C450 - Audio but no video

So, help us understand: no backlight, but you can still see image, but you DO have backlight when cable disconnected? You might be able to jumper the BL ON/OFF permanently to ON. This might cause the screen to flicker when the set turns on/off or changes sources, but it's not a big deal if you can live with that.

That's right tom66.

I don't mind a flicker. How would I go about jumpering the BL ON/OFF?

[tom66]

Re: Samsung LN32C450 - Audio but no video

OK, post a clear picture of the label next to the connector between main and power board (on power board side) and of the connector assembly on each end. Simply disconnecting the wire for BL ON will cause the power board to pull the signal HIGH every time the TV is powered up so the backlight should come on.

[Aulus]

Re: Samsung LN32C450 - Audio but no video

Ok here are the pictures, this is fun. Let me know what's next.

Can you help me with an amateur question? Does the pin diagram correspond to how the wires go into the circuit on the board? If this is the case wouldn't the power board side picture with the D/C cable mean that as I look at the connector that the 2nd pin down from the top right would be the BLU_ON pin #4? I'm having a hard time trying to describe from the picture where it's at.

[tom66]

Re: Samsung LN32C450 - Audio but no video

I think it's the 4th wire, basically the wires are numbered in zig-zag fashion

2 1
4 3
6 5
8 7
...
18 17

Make sure to cut the wire such that it can be reconnected should the wrong wire be accidentally cut.

[newtothis]

Re: Samsung LN32C450 - Audio but no video

Ok here are the pictures, this is fun. Let me know what's next.

Can you help me with an amateur question? Does the pin diagram correspond to how the wires go into the circuit on the board? If this is the case wouldn't the power board side picture with the D/C cable mean that as I look at the connector that the 2nd pin down from the top right would be the BLU_ON pin #4? I'm having a hard time trying to describe from the picture where it's at.

Yes that is correct.

*** EDIT *** As per, Tom got there first

[Aulus]

Re: Samsung LN32C450 - Audio but no video

I think it's the 4th wire, basically the wires are numbered in zig-zag fashion

2 1
4 3
6 5
8 7
...
18 17

Make sure to cut the wire such that it can be reconnected should the wrong wire be accidentally cut.

Something odd happened and it wasn't that it works, hah.

So now when I turn off the TV the backlight flickers once. This does not happen when powering on the TV. Also, when I plug/unplug the main board cable it flickers once. I am no longer getting the constant backlight upon main board cable D/C.

Let me know where to go from here

[newtothis]

Re: Samsung LN32C450 - Audio but no video

Something odd happened and it wasn't that it works, hah.

So now when I turn off the TV the backlight flickers once. This does not happen when powering on the TV. Also, when I plug/unplug the main board cable it flickers once. I am no longer getting the constant backlight upon main board cable D/C.

Let me know where to go from here

So no connection at all from PSU to main and now no backlights?

[tom66]

Re: Samsung LN32C450 - Audio but no video

Hmm, OK, connect the wire as usual, back to no backlight? Perhaps you had original symptom before, but it was intermittent? Check all bulb connectors, etc.

[Aulus]

Re: Samsung LN32C450 - Audio but no video

Well that was correct, but now all of a sudden after unplugging the AC for a while it went back to turning on the backlight when the PSU-Main cable is D/C.

The symptom that I've seen change is that upon turning off the TV it now flickers the backlight once, then stays dark.