Technosonic LCD3201 No Picture

[bootlegger17]

I have been given a Technosonic LCD3201 TV that has no picture.
Symptoms are Powers up, screen is backlit, there is sound from the video source, but no picture. There are no onscreen controls either.
Having trawled google, it seems a common issue with this model, and it is recommended to replace the t/con board. Also, to check the Fuse on the input of the t/con board (and the power stabiliser). I have checked the fuse and that is OK. Is it possible to check the Power stabilisers without power, as re-assembling this and getting to the board for testing when powered up would be nigh-on impossible.

Having dismantled the TV and removed all the boards, I noticed that the video input board seems to power the t/con board. Further inspection of this video source board makes me a little suspect that it may be this board and not the t/con board afterall, as there appears to be some strange markings around some of the caps. See attached screen shots.
I have not come across caps like this before, but does this look like a leaked cap for this type of capacitor, or can these not leak and is this marking part of the assembly process?

Any other ideas for proving which board is at fault?
Seems this t/con board is common amongst many 32 inch TVs also.

Regards
Jason

[Clydeuk]

Re: Technosonic LCD3201 No Picture

That looks like some kind of gluey substance to me. These type of capacitors don't leak like electrolytics do. You really need to test whether the T-CON is getting the 12v supply.

[Clydeuk]

Re: Technosonic LCD3201 No Picture

By the way that section in the picture is the audio output stage, which you have established is fine.

[bootlegger17]

Re: Technosonic LCD3201 No Picture

thanks ClydeUK.
I have managed to re-assemble the TV with the TCon board brought through and laid on top so I can do some further testing.
It would appear testing the fuse that it runs as +5v not 12v.
Various other test points like on the power stabilisers seem to have around 3.5 or 5v lines on them. Not sure what they should be - i will work out their reference number and download a manual for them to identify what pins should be outputting what values.
I have not been able to locate a service manual for this particular board alone, but I can find a whole assembly reference manual for the combined LCD and tcon board - it would appear it is sold as one unit, but this doesnt go indepth enough on the tcon board.
As for the pics, you are half right. Of the three connectors, only the middle one is the speakers - the other two are lines from the power pack. I havent traced the lines from what I thought was a leaky cap, but it is likely looking at it, that this powers the speakers, and as I mentioned, the sound is good, so you are probably right on that assumption that this section is ok. I guess its back to looking further at the tcon board.

Regards
Jason

[bootlegger17]

Re: Technosonic LCD3201 No Picture

The 3 regulators I have are :
L117DG NIKOS 085912097 pin 3 vin=5.10v pin 2 vout=3.53v pin 1 gnd=0 big ground 3.53v
MMC6100B 25 F538 pin 3 vin=3.53 pin 2 vout=0.83v pin 1 gnd=0 big ground 0.83v
AK33P 02C59 pin 3 vin=5.1v pin 2 vout=3.27v pin 1 gnd=0 big ground 3.27v

Looking at the guides, I am unsure how I am supposed to know the vin and vout from this as they seem they could be variable.
But at least all three seem to confirm that each vin is something and each vout is something smaller and the large ground seems to match the vout and all gnd pins are 0, so I suspect there is no fault here.

What else can I check to confirm the board is working?

There are a few test points on the board.
POW_ON = 0.1V
GVOFF=3.13V
GVON=0.14V

Jason

[bootlegger17]

Re: Technosonic LCD3201 No Picture

Gutted

After much testing and thinking I cant find a fault with the tcon board, i placed the tcon back inline and turned on the TV (whilst still unassembled) and to my suprise, the screen came on and I could see some menu dialogs! Woohoo i thought.
I started re-assembling the screen, but annoyingly due to limited space, i struggled with it face down on a small desk and I heard a crack. Looked at the screen but could not see any issue. Continued to re-assemble and powered up and........ I had bust the screen.
Oh well - a tad annoying I have to say, but I was beginning to wonder what I was going to do with the screen anyway. I was given it as a freebie because it was broke. If nothing else, it will be good for spares to sell on ebay. Every cloud has a silver lining.....

What I have discoverd throughout this process is I need a bigger work room......roll on the garage conversion me thinks.....

So, anyone who has this same issue with no screen, may wish to consider simply pulling apart, cleaning and re-seating all the plugs, as that is technically all I had done to get this working. Actually no faulty part it would appear.

Consider this case now closed!

Thanks for all the input anyway.

Regards
Jason