Samsung 32" LN32C450E1D red light, but no power on.

[Naturallyk2]

Initially when I got this TV, I thought maybe some caps were bad on the power board. I don't see any bulging or leakage of the caps on the power board so now I'm kind of wondering where to start. I searched through the forums to see if anyone else had the same problem, but I guess mine is different from the other postings.

1. When plugged in, the standby light comes on.
2. The TV will not power on by pressing the power button or using the remote.

Thanks for the help gents. I've been messing around with TVs for a little while and I'm still only at the beginner level and that's usually replacing bad caps. I got lucky on one TV (a Sceptre 32") and fixed it by replacing the EEPROM chip.

[Naturallyk2]

I took out the main board and noticed something strange. It almost looks like condensation had built up and ultimately effected the mainboard. I see a bunch of grayish traces running everywhere on the back of the mainboard. Looks kind of like light dust? I can wipe it off, but notice the river of gray bubbles. Anyone seen anything like that before?

[budm]

That is just no-clean flux residue.
What DC voltage do you have right at the two legs of the main filter cap (big yellow cap laying on its side), it should have around 160VDC when TV is OFF and should jump up to >360VDC when power switch is activated.

[Naturallyk2]

The voltage I'm getting is 380VDC that stays there for a brief moment then trickles down to ~320VDC and then shoots back up to 380VDC and the TV isn't turned on. I can't turn the TV on either via power button or remote.

[budm]

Voltage testing is right at the two legs of the cap, you are working in the primary side of the circuit so you cannot use chassis as the ground ref point, the primary circuit GND ref point is the negative leg of the main filter cap.
It sounds like the PS_ON signal is going high and low.
You will need to check the standby power supply first, and then the PS_ON signal, see the diagram I posted.

[Naturallyk2]

My apologies, I caught the GND ref point in your "NOTE" on your troubleshooting post. The voltages I gave you were from using your negative lead on the filter cap as ref.
As far as the standby power supply, I'm already lost in the schematic you sent me. Sigh.

[Naturallyk2]

I checked the PS_ON signal and it's at 0.72VDC (TV off). Not sure where to start on the standby power supply on checking that.

[budm]

So when you hit the power button, does the PS_ON go up to more than 2.5V?
5V Standby (B5V) is on the connector CN802 pin 11, 13, and 14 (see diagram page 2).
You will use the chassis for the ground ref point because you are now testing the Voltage in the secondary side, make sure not to touch any on the board with your hands or body.

[Naturallyk2]

CN802 11, 13, and 14 measure at 1.83V. PS_ON does not go up to more than 2.5V when I press the power button. In fact, it just hops between .778V to .013V on its own. The power button has no effect. I will note that the input panel on the TV is "touch" not "press." The only way I get 11, 13, and 14 to read at ~5V is when I jump 16 (A5V) to 14. That's when all of them read 5V. Then when I jump GND to 14, then B5V's will read 1.83V again. I found that out by accident.

[Naturallyk2]

Originally Posted by budm

So when you hit the power button, does the PS_ON go up to more than 2.5V?
5V Standby (B5V) is on the connector CN802 pin 11, 13, and 14 (see diagram page 2).
You will use the chassis for the ground ref point because you are now testing the Voltage in the secondary side, make sure not to touch any on the board with your hands or body.

I took a shot in the dark on this one and ended up finding a youtube video on this power supply issue. I measured the voltage across CM852 and was only getting 9.42VDC when looking at the schematic, I should be getting 24VDC.

The youtube video that lead me to this is https://www.youtube.com/watch?v=ASMOVbOZac0

Take a look at the highlighted schematics and tell me if my tracing is correct. I'm tracing it from the CM808 to CN803 pins 10,11,12,13, 14. All of the pins read 9.42VDC. (I used the chassis as ground ref since it's on the cold side thanks to your note once again)

The question: is CM808 bad? Thanks for being patient with me BUDM. I'm picking it all up pretty quick, but still have a lot to learn.

[budm]

Cap CM808 (coupling/DC blocking cap for drving the 24V transformer) is the common failure, check its capacitance. you will need to remove it to check the capacitance, it is special kind of cap.

[Naturallyk2]

I just removed CM808 and it's open. Imagine that. Am I pulling the voltage from ICM801 then? Is that the voltage I'm seeing on CN803 pins 11-14?

[budm]

Cap will show open circuit (using Ohm meter) if it is good, you need to check its CAPACITANCE.
When the capacitance drops, the transformer will not receive the correct drive voltage (< than what it should have) to drive the transformer.

[Naturallyk2]

Says 0nF . I only have the polarized capacitor symbol on my multimeter though. I'm sure that doesn't matter, right?

[budm]

Correct, it is 0.018uF 630V High pulse withstanding cap.
They are hard to get, see if this one will fit your board:
http://www.digikey.com/product-detai...2122-ND/585189
I would go with higher voltage:
http://www.digikey.com/product-detai...258-ND/2179295

[Naturallyk2]

We'll see. I ordered the part. Will get back to you after I get it in and replace it. Thanks BUDM.

[Naturallyk2]

Boom! Ordered the part and problem solved! Thanks BUDM for sticking with me on this one. Also, thanks for replying slowly to my thread because it made me search even harder and learn even more! I'm pretty thankful for that .

[budm]

Well, good job ad thanks for the repair feedback, another TV saved form landfill, now you can find more and spend <$5 for repair.
I also would like to keep track on this cap to see how well it holds up compared to the original.

[LarryHuff]

Great thread. I have the same Samsung tv that exhibited the same problem. Having dealt with open or shorted electrolytics for years I was pretty confident the problem would be obvious when I took the back off the set. I was sad to see no puffy or leaking capacitors. I decided to remove all of the electrolytics and test them. All were good. One step closer to the dumpster.

I decided to do a little more research and went on to the second page in my google search. I happened upon this forum which described my issue to a “T”. I remove CM808 and it measured 20pf. Open actually. Fortunately I had on hand .02uf @ 600 v and decided to give it a try. Presto, the set fires up and works like a charm.

I likely should order a higher voltage cap in the future but for now I’ve managed to save the landfill one more tv for the sake of a $1 component.

Thanks for the info and schematic. It made my day.

[budm]

Originally Posted by LarryHuff

Great thread. I have the same Samsung tv that exhibited the same problem. Having dealt with open or shorted electrolytics for years I was pretty confident the problem would be obvious when I took the back off the set. I was sad to see no puffy or leaking capacitors. I decided to remove all of the electrolytics and test them. All were good. One step closer to the dumpster.

I decided to do a little more research and went on to the second page in my google search. I happened upon this forum which described my issue to a “T”. I remove CM808 and it measured 20pf. Open actually. Fortunately I had on hand .02uf @ 600 v and decided to give it a try. Presto, the set fires up and works like a charm.

I likely should order a higher voltage cap in the future but for now I’ve managed to save the landfill one more tv for the sake of a $1 component.

Thanks for the info and schematic. It made my day.

Thanks for the repair report, glad the thread helps solving the problem.