Emerson LC320EM8 - won't power on, two green blinks then red Standby

[abd_ga]

Good evening to all,

I'm attempting my first LCD TV repair, an Emerson LC320EM8 that I bought at a garage sale yesterday. I downloaded the manual from Funai but don't see any information on power LED error codes. The power LED immediately is red upon applying AC. When attempting to power on, there are two green blinks then it returns to solid red. Any error code information or if you see anything suspicious in the pictures, I'd appreciate any feedback. I searched on Emerson and Funai in the forums to see if there's much info. and didn't find any related threads.

I disconnected the different board loads (inverter, TCON, ATI-based digital, speakers) to see if the behavior changes. No change in symptoms. I also noticed an audible short duration buzz when removing AC after a power on button cycle, somewhere in the AC/DC conversion section of the power supply/video out board, but haven't been able to pinpoint the component.

I don't see any bulging capacitors (mostly Nichicon), nor any burnt or damaged resistors/diodes/ceramic caps/semiconductors. There is some flux residue on the bottom side in a few spots, but again, nothing that catches my eye as a potential problem.

I have a handheld DVM and a scope and am willing to probe but am also without schematic, so any pointers are greatly appreciated. Thanks.


-Adam

[cadiman]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

When you power up the tv does the screen light up for a quick second? Inverter problems are common. (turn lights down /off when doing this)

You need to see if you are getting any voltage to the inverter upon power up.

On these sets you may still have audio even if picture is out.

1) Is the inverter shutting down power supply? (not always on these)

2) Is the power supply faulty? Missing voltage 5v,12v,and 24v
5v is always on (control) Yours seems to be working.
12v runs audio and other things
24v is for inverter
when turning on the tv the mainboard tells the power supply to turn on 12 and 24v It uses the 5v standby voltage to do this.

3)Is the main board not working properly?

I am not an expert, but somehow I fix these things. Hope this helps a bit.
Good luck!

[abd_ga]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

Thanks, cadiman.

There is no brief backlight -- the on/off cycle occurs quickly. Here are the voltages that I've examined so far:

+3.3V_standby is always present.
+3.3V attempts to ramp up but quickly settles at +1.9V.
+5V doesn't ramp.
+12V -- I'm looking for a probe location.
+24V doesn't ramp.

I don't understand the power supply topology yet, but it appears to be something common to multiple outputs.

I checked the inverter transformers and all have continuity and I resoldered their joints when the board was first removed.

I took another look for component damage and the only thing that I see is one power transistor which a marred package (pictured attached). I can't make out the markings (K9563?).

Any other ideas are appreciated.

Regards,
Adam

[PlainBill]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

Thanks, cadiman.

There is no brief backlight -- the on/off cycle occurs quickly. Here are the voltages that I've examined so far:

+3.3V_standby is always present.
+3.3V attempts to ramp up but quickly settles at +1.9V.
+5V doesn't ramp.
+12V -- I'm looking for a probe location.
+24V doesn't ramp.

I don't understand the power supply topology yet, but it appears to be something common to multiple outputs.

I checked the inverter transformers and all have continuity and I resoldered their joints when the board was first removed.

I took another look for component damage and the only thing that I see is one power transistor which a marred package (pictured attached). I can't make out the markings (K9563?).

Any other ideas are appreciated.

Regards,
Adam

The transistor in question is probably a 2SK956. Troubleshooting is complicated because there is no clear deliniation between the power supply and the load.

<Rant mode ON> I suggest you ignore the TV for a few minutes and concentrate on the pictures you have provided. Frankly, they provide very little information to anyone trying to help you. The TV seems to have three boards; only one is shown. The one board appears to contain the power supply and inputs, but no signal processing components. The resolution is so poor and the glare so bad that tracing anything is impossible. <Rant mode OFF>

Some clues: This has a dual power supply. The smaller transformer is for the standby supply; the larger would be for the main supply. The transistor you suspect appears to be the switch for the standby supply. The main supply's power FET is probably on the large heat sink near the main filter cap. Note the clear signs of overheating at the upper left of the main power transformer. The fact that the main 3.3V supply settles at 1.9V while other voltages don't attempt to rise indicates an overload in one of the supplies that won't rise.

PlainBill

[abd_ga]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

Thanks for your help, PlainBill,

Sorry for the picture frustrations. I thought I followed the guidelines for pixel resolution (approximately 700 pixels wide). My camera doesn't have a macro mode and I took 20-25 pictures under the best lighting I could provide at the time. Will try again and repost new pictures if I get better results (will try the bright sunlight option, weather permitting).



Regards,
Adam

[abd_ga]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

I've tried taking additional pictures with a different camera under the brightest lighting I could provide (no sunlight, using an 800W dual worklight). They've been cropped/resized to approximately 1000 pixel widths. I marked the areas on the bottom of the power section that look overstressed/ overheated.

I measured the resistance from each DC output to GND to see if there's a low ohm short but nothing was below 200 ohms except for the +1.2V core voltage on the logic board which, at ~10 ohms, is reasonable from my digital experience.

I'll try to check the DC outputs with an oscilloscope later today, but wanted to see if these pictures are any more usable and yield any other clues.

Thanks for reading!

Regards,
Adam

[PlainBill]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

I've tried taking additional pictures with a different camera under the brightest lighting I could provide (no sunlight, using an 800W dual worklight). They've been cropped/resized to approximately 1000 pixel widths. I marked the areas on the bottom of the power section that look overstressed/ overheated.

I measured the resistance from each DC output to GND to see if there's a low ohm short but nothing was below 200 ohms except for the +1.2V core voltage on the logic board which, at ~10 ohms, is reasonable from my digital experience.

I'll try to check the DC outputs with an oscilloscope later today, but wanted to see if these pictures are any more usable and yield any other clues.

Thanks for reading!

Regards,
Adam

Better pictures. Unfortunately, the only bright idea I had was to try disconnecting the inverter.

Ordinarily I suggest disconnecting all loads from the power supply and providing the turn-on voltage to see if everything comes up. That wouldn't be easy in this case.

PlainBill

[abd_ga]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

Thanks, Plainbill,
I just located a service manual that has all schematics, PCB artworks and bill of materials, so I'll study a bit and should have a better shot at probing. Will post an update in the next few days. Is the service manual something that typically gets attached for others to reference? Thanks again.

Regards,
Adam

[PlainBill]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

Thanks, Plainbill,
I just located a service manual that has all schematics, PCB artworks and bill of materials, so I'll study a bit and should have a better shot at probing. Will post an update in the next few days. Is the service manual something that typically gets attached for others to reference? Thanks again.

Regards,
Adam

That's good news. I usually suggest posting a link, but attaching the manual itself is also good.

PlainBill

[ramzzey13]

Re: Emerson LC320EM8 - won't power on, two green blinks then red Standby

Hello, I am new to this forum with little tv repair experience but I am always fascinated with electronics and willing to learn and fix, and that's all it takes!
But I have this same exact TV with the same exact problem as described by abd_ga. With the only difference being, I leave the TV unplugged and randomly (I mean every 3 weeks or so) when I plug it in (without hitting the power button) it turns on and will stay on until I power it down. Any ideas or more preferably any update with your fix? Thanks so much and Hello!

ramzzey13