Emerson/Funai LF46EM4 no image

[Josh86]

(LF461EM4) Initially this 46" LCD was shutting down on me after the Emerson logo and channel display. Through the info of another thread here I decided to look at the backlighting and found that the center row of LEDs were out (LG branded). Bought a Samsung branded replacement on eBay and it works. It no longer shuts off with a blinking front LED sequence.

However, at some point during disassembly or reassembly of the front panel I must have done something because the display no longer shows anything. My first thought was I damaged some part of the LCD or connectors...but then I thought I should listen for audio on an input source to verify. Plugged in the audio/video RCA leads from a game console and cycled through sources (without visual) and I didn't hear anything coming through at all. The only sound change I hear is the slight change in pitch from the transformers on the PSupply board when cycling the source button. I also see my backlighting change brightness slightly when cycling sources.

At the supply board I have what I assume is normal voltage for the 21v power on and the 3.3v standby/always on. I haven't really checked anything on the main board because I'm not sure what I should be looking for. It's definitely getting voltage though. Also I had a small crimp in my cable from main to the T-Con(?) but it's no worse the the folds from the factory. I started checking continuity on that but kinda gave up after the 10th pin.

Initially I was just going to order a new main board but I had a a hard time finding one...which the LEDs were the primary issue anyway. Kinda back to where I started but a different problem. I see some people offer online/mail in repair services for these boards if that is the issue.

Any advice for troubleshooting and testing would be appreciated. Hoping I can salvage it and put it upstairs as a game and movie TV for me and the kids. Sorry for the essay, I like to be descriptive and usually find that putting all the info out there helps get the problem solved quicker.

PSupply board: BA3AU0F0102
Main: BA31T0G02013
Starting Serial # DS2

And yes, I'm aware it's a cheap unreliable off-brand...but I like to fix things if it's worth it.

[budm]

Re: Emerson/Funai LF46EM4 no image

Did you verify that you do have 12V on both ends of the SMD fuse on the T-CON board?
Upload good clear pictures of YOUR boards will also help.

[CapLeaker]

Re: Emerson/Funai LF46EM4 no image

Also verify the LVDS cable being correct way installed not backwards.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

Did you verify that you do have 12V on both ends of the SMD fuse on the T-CON board?
Upload good clear pictures of YOUR boards will also help.

I do not have any voltage across F1 when the TV is powered. I get ~3V when I measure from either side of the fuse to the chassis and a little less to a ground on the T-Con board. I have continuity across the fuse. Everything on that board is surface mounted and I didn't see any other fuses on that board. Image attached.

I noted that the LVDS cable feels pretty hot on the pin 1 side (unless that's normal, cable is rated for 105 C). It's not inserted backwards.

[budm]

Re: Emerson/Funai LF46EM4 no image

Trace out which pin on the T-CON board side is connected to the T-CON SMD fuse and then remove the LVDS cable from the T-CON, that pin should go back to the main board whisch where you see if it has 12V or not when T-CON board is not connected.
Right now it is either there bad circuit on the main board or the T-CON is loading down the switched 12V, it will require in-depth reverse engineering to trace out the connection tio get down to component level, I hope you do know electronics well enough to accomplish the task.
BTW: 'I do not have any voltage across F1 when the TV is powered." That is because the fuse does not have open circuit (bad blown fuse).

[Josh86]

Re: Emerson/Funai LF46EM4 no image

BTW: 'I do not have any voltage across F1 when the TV is powered." That is because the fuse does not have open circuit (bad blown fuse).

Yeesh, sorry, even I know better you can't get a reference to anything like that. Not thinking. I took some circuit analysis and DSP long ago but never really used it. This is about as much practice as I get...when I feel like trying to fix some broken thing a couple times a year.

So might have to take a step back.

I removed the TCon board for better lighting and access with my multimeter. Rung out pins (1 and 4 connected to fuse). Have 12V on pins 1 and 4 out of mainboard to end of LVDS. Hooked TCon back to mainboard and LCD panel to check voltage on pin 4. Got 12V. Checked pin 1...also 12V AND both sides of fuse read 12V now. LVDS cable isn't getting hot anymore either. Noticed the power supply board wasn't as noisy either. Wondering if a cable was not seated well or something else shorting a connection.

Got excited and lifted up the display...but no picture still. So now I'm sitting at 12V power to TCon and wondering what to do next.

[budm]

Re: Emerson/Funai LF46EM4 no image

There are two cables between the T-CON board and the LCD panel, try having it connected one a time to see if you will get good picture on half of the screen or not.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

There are two cables between the T-CON board and the LCD panel, try having it connected one a time to see if you will get good picture on half of the screen or not.

Half of the panel completely white, the other half black with one connected. Same with both cables. When both are connected it looks just the same as when they are both disconnected (black screen).

Attached main and supply board pics -- couldn't do it from wife's old iPad earlier. Attachments from photos on iOS just automatically name every file "image" when uploading and overwrites multiple files, just leaving you with the last uploaded.

[budm]

Re: Emerson/Funai LF46EM4 no image

Can we see the pictures of the T-CON board?

[Josh86]

Re: Emerson/Funai LF46EM4 no image

Can we see the pictures of the T-CON board?

Attached again. Let me know if you want detail of anything and I might be able to use a DSLR to get a closer high res pic. Would it be worth checking for audio again on an input since I'm getting normal voltage to the TCon now?

[Josh86]

Re: Emerson/Funai LF46EM4 no image

I've tried checking for sound with an input source but with no luck.

Is it possible it's still the T-Con board in this situation or is that a sure sign it's the mainboard? I don't know anything about how the logic works between any of the chips/boards without seeing a block diagram (and even then I may not understand it), but I wonder if the mainboard wants to see/confirm some output from the T-Con coming back for everything to work (including audio output). If anyone knows of a link to a service manual for this line of units, that'd be cool to look at.

A new T-Con can be had for $20 or less it seems, whereas the mainboard is just hard to find, expensive, or will have to go to someone for a repair (~$50 average). The only other common parts I am seeing for a mainboard fix is an EEPROM IC. EBay does have a 20% sale today and I could use that on a mail-in repair service to get the cost down a little.

On the flip side, I like tinkering and it would be fun to find out exactly what isn't working (I'm not necessarily in a hurry) and I could desolder and put a new component in as long as it wasn't too small. I live in a very rural area and before Radioshack became defunct it was really the only local place to get electronics. I'd be ordering pieces online if I were to replace anything on a circuit board (can't even buy a simple resistor anywhere in 100 miles unless I salvage it from something).

So, if not I'm not replacing either board entirely, I can take my time trying to figure it out. If nothing comes of this I'll end up throwing the set away in the future unless anyone is interested in parts.

[budm]

Re: Emerson/Funai LF46EM4 no image

I can see some Voltage test points on the T-CON.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

I can see some Voltage test points on the T-CON.

Reattached marked up image with voltage reads.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

Reattached marked up image with voltage reads.

So looking at the reads I thought "where is CPV1 if I'm reading CPV2"? I then realized I actually never read CPV2; I used the top test point which was likely for CPV3. I completely ignored all the rest of the labels and just looked at that highlighted box -- whoops.

If you really need CPV2 (I assume it's an important signal), I'll have to wait until I'm back home to check it out and I'll record all those values on those test points. In the meantime, if there are any other points you want me to check (either here or on mainboard) I'll note those and get the reads.

Really appreciate the direction/help.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

Remeasured and the CPV testpoint area reads as follows:

CPV3 = 2.407 (taken the day before)
CPV4 = 2.37 V
STV2 = 2.37 V
CPV1 = 2.37 V
(?) USI_SYNC = 1.77 V
CPV2 = 2.11 V

[Andrew F. Ali]

Re: Emerson/Funai LF46EM4 no image

Some of those T-CON Bd readings are off. I think you should get anew T-CON Bd and give it a try.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

Some of those T-CON Bd readings are off. I think you should get anew T-CON Bd and give it a try.

Which voltage readings do you suspect are abnormal from expected voltage? This way I can retest and confirm before before I order a new T-Con board.

Thanks!

[Andrew F. Ali]

Re: Emerson/Funai LF46EM4 no image

.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

I can certainly order a T-Con, though I'm concerned it may not work because I'm not getting any audio output over composite/component. I can't find a service manual for these Funai 46" sets (either Emerson or Magnavox) but I looked at some schematics and block diagrams from both 32" and 39" Funai sets and I don't see anything going over the LVDS to the T-Con that has much to do with the audio interface on the L/R inputs.

I guess I'd just like my concerns to be proved wrong or explained -- because a $20 T-Con would be great if it were to fix the problem. I just have a gut feeling there something on the mainboard and finding or fixing that is a lot more hassle.

Really wish I had a service manual specific to this model type -- but I think I'll take a look at the Funai 39" service manual to see if there's similarities in testing.

[Josh86]

Re: Emerson/Funai LF46EM4 no image

Haven't been able to look at the set for about a week but...

I'm ordering a t-con board because they can be had for ~$10.

I went through the troubleshooting flowchart on a 39" Funai (all the connectors/pinouts identified the same) and I end up with the result that it's either the mainboard or a bad panel. The "no video" tests had me check for certain voltages at specific pins on both the mainboard and connection to the t-con. They ended up coming out as expected which leads to the suggestion of replacing the main CBA or a defective/bad panel. I fear the latter because I moved it around a bit during disassembly to fix the bad backlighting. Maybe there's a short to the aluminum framing; who knows. I could pull it back out of the chassis and see.

Before I put the t-con in I'm going to check the only FET on the t-con board. I read some other posts (and saw the shopjimmy video) about how a bad panel can often be the cause of damage to the t-con.

I'm still a little concerned in the case of either a bad t-con or bad panel that I'm still not getting any audio, which I can't see that issue being anything but something on the main CBA board.