Emerson LC39LEM3

[marlboroa]

I have a 39" emerson that blows the fuse as soon as its pluged in. IF I unplug the digital board that connects to the power supply then the fuse will not blow. I unpluged everything from the digital board and pluged it back into the power supply and it will blow the fuse again.
So where can i start testing on that board to find out what is doing it?

[vinceroger69]

Re: Emerson LC39LEM3

can you post some pictures up?

[selldoor]

Re: Emerson LC391EM3

you have got the model number wrong - not a good start

Emerson LC391EM3

[marlboroa]

Re: Emerson LC39LEM3

pics not the best but you get the idea. I can leave the black/red wires on the power supply connected and the fuse will not blow.

[selldoor]

Re: Emerson LC39LEM3

What is the part numbers of the 4 x 8 leg components near the connector from main to power. Have you checked the cable/socket for shorts bent pins

[selldoor]

Re: Emerson LC391EM3

In order to stop wasting fuses, can you get a lampholder and a 60watt filament lamp.
Solder that across the fuse and if there is a short the bulb will light and stay bright if no short it will light then start to dim.
I ask because I want you to disconnect the black and red wire socket and try with the main board and power board connected.
If my thought is wrong then you will blow another fuse.
I believe the Black and red carry the voltgage to another board - not pictured - the inverter board. It is possible that the main board is ok but when it sends the signal to switch on the voltage for the backlight, if there is a problem/short on the inverter board it is causing the fuse to blow.
I would like to see a pic of the inverter board before trying to check out the main board.

[marlboroa]

Re: Emerson LC39LEM3

I tried what you said and had everything connected but the black and red wires that go to the inverter. Still blew the fuse as soon as it was pluged in.

[tom66]

Re: Emerson LC39LEM3

The fuse should be removed before putting the bulb across it.

[marlboroa]

Re: Emerson LC39LEM3

i know, i dont have a lamp socket handy. ill have to pick one up later but i do have more fuses and a resetable fuse. kinda like a circuit breaker.

[selldoor]

Re: Emerson LC39LEM3

Ok well it looks like its almost certainly the mainboard unless you have been testing it with the boards touching the frame or a conductive surface.
Really could do with a good clear picture of the board front and back.
Good light without flash is the key.

[selldoor]

Re: Emerson LC39LEM3

Sorry double post
Oh yes and the part numbers of the 8 legged components
see post5

[tom66]

Re: Emerson LC39LEM3

Not so fast... an issue with how the PSU works could be causing it to fail when the PSU switches on under command from the main board.

[marlboroa]

Re: Emerson LC39LEM3

Ok heres some pics. If these are the parts you wanted then 3 are the same M2305sds and the one right in front of the connector is the one that starts with 001cow. the connectors are all good and the boards have not been touching the frame.

[MisterD]

Re: Emerson LC39LEM3

In your pictures I can see that the Main Board has no mounting screws and is slid over to the right shorting it out to the chassis.

[marlboroa]

Re: Emerson LC39LEM3

yea i just took those out right before the pic. I was going to take a pic of the backside but got distracted by the kids. The screws were in it for testing.

[selldoor]

Re: Emerson LC39LEM3

Cant find much info on those components.
Tom seems to think it may still be a power supply problem, I guess along similar lines to what I was thinking with the inverter. It starts off ok then
when the main board signals to start higher voltage it goes bad.
There are quite a few diodes on there perhaps start by checking them for shorts.
This guide by retiredcapshas quite a lot of component tests most without power to the board start at post19
https://www.badcaps.net/forum/showthread.php?t=10419

[budm]

Re: Emerson LC39LEM3

When the Main send out the PS_ON and Inverter ON command to the power supply board, the PFC circuits will kick on (there are two MOSFETs and two inductors on the top edge of the board as shown in the picture). The large transformer close to the bottom right is an inverter transformer that driven by the MOSFET to step up the voltage (not at CCFL voltage level) to drive the primary side of a bunch of smaller inverter transformers which drives the lamps.
So you need to see what kind of board is which is not shown in your pictures. That is the big load big enough to blow the fuse.
Shopjimmy does not have any pictures of the sub inverter board either.
http://www.shopjimmy.com/catalogsear...erson+LC391EM3

[MisterD]

Re: Emerson LC39LEM3

http://www.ebay.com/itm/I390HJ-08A-I...item27cfd23b61

Here's the Hidden Inverter Board.

[selldoor]

Re: Emerson LC39LEM3

When the Main send out the PS_ON and Inverter ON command to the power supply board, the PFC circuits will kick on (there are two MOSFETs and two inductors on the top edge of the board as shown in the picture). The large transformer close to the bottom right is an inverter transformer that driven by the MOSFET to step up the voltage (not at CCFL voltage level) to drive the primary side of a bunch of smaller inverter transformers which drives the lamps.
So you need to see what kind of board is which is not shown in your pictures. That is the big load big enough to blow the fuse.
Shopjimmy does not have any pictures of the sub inverter board either.
http://www.shopjimmy.com/catalogsear...erson+LC391EM3

The fuse blows even when the inverter board is disconnected? Post6/7
Does that suggest a problem on the PFC circuit?

[budm]

Re: Emerson LC39LEM3

So on post 1 if no black/red wire connected it did not blow the fuse, now in post 7, it will blow the fuse without having the red/black wires connected. It sounds like it had more damage components now since then, this can be due to too much load was on the inverter circuits that try to drive shorted load. The PFC must have been OK in the beginning since it did not blow the fuse in post1. At this point he needs to check all the components mounted on the heatsink to start with.