emerson lc391em3

[HiDesertRat]

This is what I know, haven't even opened it up yet.
TV was on and working, just shut itself off.
Press ON button or use remote, the power LED flashes, you get the Emerson splash screen (very briefly) and thing shuts off again.
Can hear a click (relay?) when powered on and again when it goes to standby.

Anyone have wiring diagram/schematics or service manual? What do you think the problems could be? Bad power supply board? What is the best way to test? I don't want to just easter egg the thing, would like to be able to prove the faulty part bad before ordering.

Thanks for your assistance in advance.

[budm]

Re: emerson lc391em3

Oepn up the TV and up load good clear pictures and see if the boards used in your TV matched these:
http://www.shopjimmy.com/catalogsear...lt/?q=LC391EM3
We need to test voltages on the power supply board first.
https://www.badcaps.net/forum/showthread.php?t=39740

[HiDesertRat]

Re: emerson lc391em3

Well let me see if I can get the pictures up. They do seem to be the same boards, but have a little different part number.

By reading the PDF on the other post, I guess I will be picking up some 1157 auto lights tomorrow.











Hoping these come through okay.

[HiDesertRat]

Re: emerson lc391em3

Okay, was able to make a few checks tonight. Disconnected all the wires to the main board and leaving the power supply board. So basically, they are the only two items drawing power. If I could figure out how to disconnect the main board I would, but it sends the "on" signal to the PS board. Not sure if it has to "sense" one of the voltages from the power supply to produce a "power good signal".
When in standby there is about 7V on the 12V line, everything else seemed to be at 0V. When turned on the 5V, 12V and 17V are all good, until it shuts off again (about 3-5) seconds. I can hear and feel the relay in the center of the power supply board energize and de-energize. Seems to me the "keep alive" voltage isn't making it to that relay, but I don't have schematics of the board, so I'm not even sure of where it would come from. Is it from a feedback circuit of the relay or a feeder component from the output of the relay? What signal shuts the TV off, once it is energized? Do I just replace the PS board or could the problem be on the main board?

[HiDesertRat]

Re: emerson lc391em3

Okay, just looked at pictures I posted on here....they aren't very good. Look a lot better on my computer. Will see about resizeing and getting better views. Maybe that will help you help me....

[HiDesertRat]

Re: emerson lc391em3

okay. Unable to get better photos. Looked the PS board up and ordered one online. Will see if it was the problem or not.
Would still like to get my hands on the schematics for this TV. Would like to figure out, and repair, the faulty board.
Hell, I would just like to get to know what the damned acronyms all mean!!!

[cory1108]

Re: emerson lc391em3

Was u able to get any info on your issue? I am having similar issue with magnavox except mine continually powers on and off and will not go into standby unless I disconnect and reconnect lead to ir sensor board. Looking at pictures I believe the power boards are different but main board appear to be indentical. I have already replaced power board on my and did not resolve issue.

[HiDesertRat]

Re: emerson lc391em3

I'm still waiting for the board to come in, hopefully tomorrow. I went to your other post and saw that budm had replied to you post, requesting pictures of your TV and boards. Provide those to him, you may be surprised at what he can do with them. Make them as clear as possible, look at the thread he posted to your post.

will not go into standby unless I disconnect and reconnect lead to ir sensor board.

I would suspect the IR board or even the remote. Is there something sending a constant signal to the IR board telling the tv to turn on and off?

Tried to find a wiring diagram for your set but couldn't find one for that model number. Does your TV have a On/Off button? Does it make a difference if you use the panel button or the remote?

You disconnect the IR board, plug in the TV and it goes to standby, right? If I read the diagram of the set I was looking at correctly, when you use the panel On/Off button it applies a ground to pin 6 of the connector. If your button was stuck, it would have a ground there all the time. Thus, turning the set on and off. It is just a shot, but check the button out.

If that isn't it. Maybe you can leave the IR board disconnect and manually apply a ground to the pin to see if the set will come on and stay on. Don't leave the ground connected, it is just supposed to be a momentary application of ground.

Good luck, I will follow your other post....got me interested....

[budm]

Re: emerson lc391em3

OK, you may have the problem either on the inverter board:
http://www.shopjimmy.com/cmo-27-d069...-inverter.htm#
or lamps problem.
Please take the resistance reading on the inverter transformer,
Just do any one of them for me so I can figure out the pin out of the transformer first, set the meter to 2K Ohm range.
pin 1 and 3
Pin 2 and 4
Picture provided by SJ.

[HiDesertRat]

Re: emerson lc391em3

Thanks Bud, I will do that. First let me blow off a little steam....

Got the PS board today and installed it. Lo and behold, same problem. TV comes on, Emerson splash screen and goes off. LED blinks while TV is coming on and then goes solid when it shuts off (standby).

Disconnected all connectors I thought I could get away with, so left IR, Main and PS connected together. Same results.

Disconnected IR, so now only PS and Main connected. Shorted pins on Main to get TV to come on. Same results.

Assuming at this point I am missing feedback signal from somewhere....but where?

End of rant...back to troubleshooting....

@Bud: Tore TV down to inverter board. Xformers are 1-3= short 0 ohms; 2-4= .5k 500 ohms. I went ahead an measured all of them and found the top one seems to be open on pins 2-4? Symptom? I am assuming we are measuring the primary and secondary of these?

I also noticed there are pins labeled FB1 and FB2; are these feedbacks to the PS?

Thanks for your assistance. Any words of wisdom going back together with this thing would be appreciated too. Admit I was a bit apprehensive pulling the panel apart.

[budm]

Re: emerson lc391em3

Pin 2 and 4 is the high voltage winding, so if one of them shows open circuit you will get 2-second to black, only take one bad transformer or one bad lamp to cause shutdown.
All of the inverter transformer winding resistance on pin 2 and 4 should be all within 3% from each other.
BTW, those lamps show sign of worn due to the face that they have blackened ends and that will cause them to draw lots of current.

[HiDesertRat]

Re: emerson lc391em3

Okay. I feel good that we may have found something wrong, which is a good thing. Is an open on 2 to 4 a indication of bad lamp or bad transformer? I was assuming it was the transformer, but figured I had better ask if the lamp would affect the reading or not.

So, if I were to connect everything back together; minus the LCD panel all the back lights should come on? More then likely the top one will not work. Or am I asking for more trouble then it is worth to try this?

Thank you, kind sir, for your assistance. It truly is appreciated!

[budm]

Re: emerson lc391em3

You can connect everything back up, the transformer with open winding may still light up the lamp for second due to the the high voltage will jump the open connection because we are dealing with something like 2000V here so the lamp may flash but will not stay on.
At this point I will get more than one transformer since one is already bad, you can expect more to go later.

[budm]

Re: emerson lc391em3

BTW, what resistance do you read on your IR board?
https://www.badcaps.net/forum/showthread.php?t=41557

[HiDesertRat]

Re: emerson lc391em3

Bud:
https://www.badcaps.net/forum/showth...t=41557&page=2

[HiDesertRat]

Re: emerson lc391em3

Well, just an update. Replaced inverter board, didn't mess with the transformer since I got a good price on board and eight lights. However, when I received the shipment six of the eight lights didn't survive.
Went ahead and tried to power up system with the bad inverter board and it did light the upper light. The light stayed on for the same amount of time the rest of them did, until the TV shut itself back down again. So not really able to verify anything there. Wish I had taken some measurements on the FB1 and FB2 terminals, but didn't.
Installed the new inverter board with the old lights, put it all back together and ...... FIXED!!!

So, thanks to everyone for their help, assistance, support and just someone to bounce things off of!

[budm]

Re: emerson lc391em3

Thanks for the repair follow-up.