Samsung LN26C450 No Picture

[CraigR]

Samsung LN26C450 I plug the set in and it makes the start-up tune and I see the red LED on front blink 6 times then stays red. I push the power button and it makes the tune again and the red LED goes out. I'm not sure if I have the sound and LED reversed for coming on/off as there is no picture or even a backlight flash on/off. I did put a powerful flashlight against the screen in both situations and could not see anything on the screen. At the PS plug I do have close to the 13V printed and over the 5V (a little)that's also printed. I wanted to try and jumper the PS to turn on the backlights but this plug I am not used to so if someone can look at the picture below and tell me what I should jumper I can try that. I also checked the fuses and all caps "look" ok. I did pull the 47uF 50V cap out and tested good with ESR meter.

[CraigR]

Re: Samsung LN26C450 No Picture

Can anybody chime in on this?

[rauno45]

Re: Samsung LN26C450 No Picture

Have you checked any other components? In some cases I have dealt with the power supply turns itself off because some component is broken(seems to be your case because you dont eaven get a flash of backlight or anything eaven, it just turns itself back off when turning on). Because it does that other components wont get harmed. First of all i would suggest replacing all crapxon capacitors if there are any. then I would check the primary side of the transformer circuit and make sure the big el cap is fine and the diodes and the rectifier is fine. When thats done i would check the voltage regulators or the IC-s or transistors or whatever it is i see mounted on the heatsinks(cant really tell). Not familiar with the backlight plug either, but if someone knows, could be worth a shot. Also have you done the hot air blower trick to eliminate its not some capacitor?

[Hombre]

Re: Samsung LN26C450 No Picture

Have you tried to disconnect mainborad from PSU? If you do that backlight could/should turn on, at least that is the case with my LE37B530.

[CraigR]

Re: Samsung LN26C450 No Picture

The PSU will need to be jumpered in order for backlights to come on and that's what I wanted to try in my first post. I did pull the caps out since then and checked with ESR meter and were all good.

[tom66]

Re: Samsung LN26C450 No Picture

On these you shouldn't have to jumper it to turn the backlight on - it will come on automatically.

[CraigR]

Re: Samsung LN26C450 No Picture

Of course you would because the power button is only connected to the main board. Otherwise I would think the light would be on all the time.

[tom66]

Re: Samsung LN26C450 No Picture

No, these power boards have built in pull up which turns backlight on automatically with connector removed, debugging aid by Samsung.

[CraigR]

Re: Samsung LN26C450 No Picture

Hmmm, well no backlight with it disconnected.

[tom66]

Re: Samsung LN26C450 No Picture

So you have a power board fault.

[CraigR]

Re: Samsung LN26C450 No Picture

Well I just went to test my voltages at the plug and all have their respective voltage and when I tested the one marked B5V it kicked on the backlights so they are lit right now and if I plug in the main then they go out so I would say PB is ok then.

[tom66]

Re: Samsung LN26C450 No Picture

Could be a cold joint on that connector possibly?

[CraigR]

Re: Samsung LN26C450 No Picture

Ok, this is odd, I was checking the (what I think) are regulators and touched 1 leg with my volt meter and the whole TV came on just like normal with a picture. have a look at the pic I attached.

[CraigR]

Re: Samsung LN26C450 No Picture

well crap, I did it 3 times but now it won't do it.

[tom66]

Re: Samsung LN26C450 No Picture

Try pressing on the BGA "Samsung" processor.
Do you have 5V standby?

[CraigR]

Re: Samsung LN26C450 No Picture

Ok, now I let it get all cold then plugged it in and just watched and after about 5 min the backlights flashed rapidly then the TV came on so maybe solder connections under the chip and when it gets warm it makes connection???

[CraigR]

Re: Samsung LN26C450 No Picture

Check all solder connections and reflowed anything on a heatsink and anything that even looked remotely questionable on both boards. Must be a heat issue as starting from a cold TV then plug in and push on that Samsung chip does nothing but let it sit and a few minutes flashes a bunch and comes on. wtf? what about those square caps on the PS? do they give problems? I took a heat gun to them and then turned TV on and only took about 15 seconds and no flashing just came on.

[CraigR]

Re: Samsung LN26C450 No Picture

Pulled those caps out of circuit and they tested ok. then pulled ALL electrolytic caps out of circuit and tested with my ESR70 and all were very good. What can i check next????

[CraigR]

Re: Samsung LN26C450 No Picture

Took a wild guess and it was a problem with the inverter board. Replaced that and is working normal now.