Emerson LC320EM3F Dead

[kevinm34232]

TV was dead, and main fuse open. Had worked on a few these before, so was hoping just a bad diode or 2. Found these usual suspects to be bad and replaced:

F601 (4A 125V)
Q601 (TK10A50D)
D610 (1ZB36 36V 1W ZENER)
D640 (SS210-TP)
R608 (PNP300JR-73-0R18)

TV still dead. Fuse is not blowing now though, and have 165VDC at main cap.

Tried replacing Q600 and IC601 photo coupler just because I had the parts. Still dead.

I suppose there may be an open resistor but I haven't found it, and down have schematic.

Anyone familiar with this one? I see many posts before, and have checked all regular failures..

[ben7]

Re: Emerson LC320EM3F Dead

Did you test anything on the secondary side yet?

Did you test those white ceramic power resistors also?

[kevinm34232]

Re: Emerson LC320EM3F Dead

Ive tested most diodes on the secondary side. Ill look some more and try to find some voltage test points.

Anyone know what chassis this model is to try to find a SM?

[kevinm34232]

Re: Emerson LC320EM3F Dead

Hmm I see, it looks like D610 36V zener shorted again.

[Ltank]

Re: Emerson LC320EM3F Dead

I have one of these sets in the shop. It tool blew the 4 amp fuse and had a shorted Q600 mosfet. I ordered the mosfet but I did now find any other issues in the primary hot section of the PS/Inverter. Hopefully my set will work when the parts are installed. If I find any other problems I will post them here for you.

[kevinm34232]

Re: Emerson LC320EM3F Dead

After lifting D610 and D607 they both still test good and I still get 165V across main cap. I tested the main board connector pins for short to ground and everything was good.

How can I further T/S now that nothing is blowing up when plugged in? I was thinking of removing the transformer T600 as when I test each cold side pin of it to cold ground it shows a short, is that normal?

[Ltank]

Re: Emerson LC320EM3F Dead

I replaced Q600 a TK10A50D mosfet and F601 4 amp fuse. it did not blow the fuse but the mosfet heatsink got hot quickly. I used my Blue Ring tester and and it shows that the T600 primary is shorted. It does not ring but ohmeter has 5 ohms on primary.
T600 is available from China for members http://ccne.mofcom.gov.cn/1069050
I will check on a spare board price and see if the customer still wants it fixed.

[kevinm34232]

Re: Emerson LC320EM3F Dead

I suspected my T600 was bad too, didn't think that was a very common issue though. Maybe I have a spare board Ill have to check.

[budm]

Re: Emerson LC320EM3F Dead

Are the Diode in the secondary side are all OK, they are known for shorting out and will cause the primary side circuit to shortout, this is about the same circuit you have worked on before but may have difference values for the parts.
This is an interesting read, I think his original problem caused by shorted in the secondary side to begin with which caused him to blow up the new parts as well. When this circuit shorted out, it will take lots of parts with it.Make sure to check the opto also.
http://elektrotanya.com/?q=hu/conten...t-start-solved
By the way the reisistance of the power transformer will show low resistance (DCR), the transformer is fed with AC so the impedance will be much higher than the DCR (DC Resistance).

[kevinm34232]

Re: Emerson LC320EM3F Dead

That was good reading, but my board does not have that diode on the secondary and I just spend an hour or so and could not find anything bad on the secondary side unfortunately. I also get no voltage on the secondary side anywhere, where I have the 165V across the main cap, so I was thinking maybe it was the transformer. Could that be a possibility?

[budm]

Re: Emerson LC320EM3F Dead

Shorted out transformer will take out the MOSFET when it tries to switched on. If it does not blow the fuse but no output in the secondary side, then the circuit is not Oscillating. The parts designator (D1, d2, q1, q2, ETC.) may not be the same as your board per diagram but the connection may be the same.

[kevinm34232]

Re: Emerson LC320EM3F Dead

I did not check if the MOSFET was getting very hot when plugged in like Ltank said, I just know I checked everything I could find to the best I could without the proper schematic for this board.

It's frustrating because the common parts that they sell as a repair kit are the ones that were bad on mine, and I have fixed a similar model before with the same parts.

I think I also remember trying to repair another Philips model when similar parts were bad and seeing the transformer burn afterwards when testing it.

I ordered a cheap board off ebay that I can use to test because Id like to find the problem and there have been others on here with same problem too.

[kevinm34232]

Re: Emerson LC320EM3F Dead

Received similar revision PS board and TV worked. Swapped the suspected transformer but that wasn't the problem. Unfortunately unable to determine what was wrong on the original board besides what I changed, so I'll run with the new PS board for $25.

Bummer, was hoping to find the fault.

[electronicsurplus]

Re: Emerson LC320EM3F Dead

If this helps anyone. We just came across an Emerson LC320EM3F and, it would power on and light up for a second then blink red light constantly

After a lot of testing voltages we found that it had a broken florescent bulb after replacing the bulb walla working again

Just thought I would ad this in the event someone comes across this problem

Obviously according to my research this is common with these TVs

[Woodysgr]

Re: Emerson LC320EM3F Dead

Does anyone have a schematic for LC320EM3F? I have a blown fuse and a bad line filter cap, but everything else checks. I expected a blown bridge or mofset, doesn't appear so.

[Woodysgr]

Re: Emerson LC320EM3F Dead

C610 to be exact.