Emerson lc320em8a inverter transformer

[Herbssat]

I currently have one of these sets that i am checking the resistance of the inverter transformers. The service manual denotes that LTZ2PCOMS008 is what the set uses. Took one off the board to check it and it measures about 425 ohms in the secondary. I ordered 2 more with the marking darfon 401724S that measure 562 ohms. I read that most read at least 500 ohms and above. The old marking has V2L Q7611. Need to know if that 425 ohm marking is correct for this inverter or does it need to be retired. Thanks.

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Hoping to get an answer on this issue soon. Thanks.

[selldoor]

Re: Emerson lc320em8a inverter transformer

What marking is on the original darfons - clear pictures would help

Hmm they dont look like Darfon transformers

[selldoor]

Re: Emerson lc320em8a inverter transformer

OK Start again the test for the inverter board is to test the secondary windings on ALL the transformers. They need to be within 3% of each other. They can be tested on the board
and any that have an odd value can be removed. I suggest you now test them all.
Make sure your meter has a good battery in.
I assume you have sound no picture and the lights flash on briefly. The problem may not be the transformers

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Thanks for the response Selldoor. Out of the 6 transformers i have one that measures about 410 ohms. The rest of them measure about 399 ohms. The one that i mentioned initially was taken out of circuit and is measuring 399 ohms also. There are also some hv blue caps that i am also going to take out of circuit. They are measuring open at t1100. I am going to put this transformer back in after i desolder those hv caps. I dont think there is anything wrong with it. I may want to check the one that reads higher in circuit.

[selldoor]

Re: Emerson lc320em8a inverter transformer

Perhaps confirm what the problem is , how does it present?

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Actually jumped the gun on this set. Seeing that this set was notorious for inverter issues i went on what the customer said without testing. According to the customer the set would play for 10 or 15 minutes then turn off. It would not turn back on until a period of time passed. I have not looked at anything on the secondary board as well. I am going to put the transformer back in and replace some components in the power section. Once i have done some detailed testing i will report back with the actual results. Thanks for your help.

[CapLeaker]

Re: Emerson lc320em8a inverter transformer

Did you actually verify if only the backlight is turning off (no picture but sound is ok) or the whole power supply is shutting down?

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Here is an update on this set. Thanks capleaker and selldoor for your responses. Put the old transformer back in and replaced 2 power resistors and fired the set up. I left the set running while checking it periodically. At about 1 hour and 40 minutes the set had shut down totally and would not turn back on. Tried to check backlight transformer by connecting 1 at a time to see if the screen would flash. All would flash but some seemed to look better than others. I wonder if these transformers still have shorted windings .

[CapLeaker]

Re: Emerson lc320em8a inverter transformer

If a transformer is shorted, it won't work. I'm want to figure out what is shutting the TV down. Let's say there would have been something wrong with the inverter, the TV would have kept playing the movie on the lcd and you would hear sound. Since the TV turns off, no no anything and back in standby, you should be looking on the power supply and the main board. So we need pictures, please!

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Thanks for the response capleaker. I will get some pictures up as soon as possible. Any other known problem areas for this set?

[kevinjo]

Re: Emerson lc320em8a inverter transformer

Does this set have big brown HV Caps?? I had one last month get too close to the inverter/transformer and had to replace it. Just an idea if yours does..good luck!

[selldoor]

Re: Emerson lc320em8a inverter transformer

I left the set running while checking it periodically. At about 1 hour and 40 minutes the set had shut down totally and would not turn back on.
Tried to check backlight transformer by connecting 1 at a time to see if the screen would flash. All would flash but some seemed to look better than others.

Dont follow that- you say it would not turn back on THEN you say you could get the backlight to flash, so it must be back on, just with no back light?
does it still have sound and can you see a dim picture with a flashlight.

Check out your soldering - re test the resistors.

I wonder if these transformers still have shorted windings .

We have had a few cases where the transformer seems ok but a test with a ringtester proves otherwise.

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Thanks for the response selldoor. I am sorry if i did not clarify myself. The tv set played fine for an 1 hour and 40 minutes. It was actually left in my basement while i made periodic checks on it. When i returned it had shut down with a dark screen and no sound. The red standby light was on but it would not turn on. If i recall the green power light would blink once or twice but the set would never turn on. While it was hot i connected one transformer and tried to turn the set on to see if the screen would flash quickly. Then disconnected that one and hooked another up to see if it would flash.This was done with all 6 transformers. My speculation is that the windings in these transformers are heating up after a certain period of time and not letting the set turn on to avoid damage. This was why i was trying to ascertain what the initial resistance of these transformers should be. I could be wrong.

[selldoor]

Re: Emerson lc320em8a inverter transformer

I suspect the power supply maybe a solder joint going out - picture might help.

Could have switched off on a sleep timer?? perhaps check next time it is on.

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Here is an update. I unplugged the 8 pin connector that goes to the mainboard from the inverter board and the set turned on. This was done after it shutdown. The sound returned also but of course no picture. Now the issue is to find out which transformer(s). I may have to order a ring tester.Kind of leery about ordering a board from ebay as the same problem might be evident.

[selldoor]

Re: Emerson lc320em8a inverter transformer

Another cheap sometimes fix is to replace the high voltage blue caps near the lamp sockets
but without a picture i dont know if there are any - any discoloured?

[CapLeaker]

Re: Emerson lc320em8a inverter transformer

something else... did you ever look at the back side of the inverter board and check the transistors on there?

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Thanks selldoor and capleaker. I looked at those hv blue caps and none seem to be discolored. I also checked the mosfets on the underside of the board in circuit and found a few with some weird readings but figured it was just reading the circuit.Those tabbed mosfets are aggravating to take out of circuit.

[Herbssat]

Re: Emerson lc320em8a inverter transformer

Got a ring tester the other day to check the inverter transformers. They all check fine with marginal q. Mosfets under the board have all been checked for resistance and they test fine. Still have that oddball transformer that has a higher resistance reading than the rest. Any other ideas?