Acer AT4220 - colour/contrast problem

[mikoz]

Hi again,
Won this 42" LCD TV on eBay for $52, that was advertised as an Acer plasma with brightness problem. I picked it up yesterday.
I'm concerned after getting it home and apart that it may have a panel issue?

The power board is a Delta dps-291ap, see this post.. https://www.badcaps.net/forum/showth...ighlight=delta

Its a well built power supply with Nichicon caps throughout none look compomised. But the primary transformer buzzes pretty loud (is that normal?) The PFC is a 270uf 450V nichicon (I didn't check the series sorry) that looks slightly domed.

The main & input boards are joined together by socket, and are scattered with Teapo caps (crap!!)

When started up the Acer splash screen displays with grey instead of green colouring and goes brighter during that 5 seconds. The source blue screen with no inputs plugged in looks normal but if you bring up the menu it is totally washed out and barely readable. I have not tried any external sources yet but was told that it is like that in component also.

Any ideas where to start the investigation?

Will upload pictures later as i am getting an internal server error 500, whenever I try.

[mikoz]

Re: Acer AT4220 - colour/contrast problem

More pictures...

[mikoz]

Re: Acer AT4220 - colour/contrast problem

Bump

[mikoz]

Re: Acer AT4220 - colour/contrast problem

So far I have tried reseating all cables. Will try hitting the main board with a hairdryer and/or freeze spray over the next few days to try and isolate the failing component.
Have ordered all panasonic FC caps for the mainboard and am awaiting delivery of them.

How do I test the main transformer that is buzzing? Should I re-flow its solder joints, as they look rather dodgy?

[Mrx3750]

Re: Acer AT4220 - colour/contrast problem

Lets see if I can help out.

Okay, you're getting a picture, so this tells me your power supply and most of the TV is working.

The color issue lies, I would think on whatever part of the chassis processes the video. Either a corrupted chip, or possibly just a software glitch.

I'm wondering if you could update the firmware on the TV. I know some TV's have USB ports in them just for firmware updating.

[mikoz]

Re: Acer AT4220 - colour/contrast problem

Thanks Mrx3750, I'm getting a picture, just a washed out contrasty bright one. I did think that it may have been a firmware issue, alas there is no service or USB port on this one. All menu items appear to work correctly, I do not have the remote for this one though and so cannot try key combinations to access a service menu yet. Waiting for one to turn up on ebay atm.
One thing more that I have noticed this morning is that if I leave the menu up on the screen > 5 minutes without change, after switching it to standby and back on it is still ghosted on the screen for a while. Signal on all input sources are affected by this issue also, not isolated to tv and component.

[Mrx3750]

Re: Acer AT4220 - colour/contrast problem

I wish you had another main board to throw in there as I'm 90% sure your LCD panel is fine as is the rest of the TV, and that the issue lies on the main board.

I'm wondering if there's a way to connect a service port.

[mikoz]

Re: Acer AT4220 - colour/contrast problem

Ive been through the service manual, which has no schematics (attached). I'm about to recap the main board with quality pan fc's to see if that might help? Just in case it is an esr issue. Just a bugger of a board 55.M34V7.002 to locate in the right revision/configuration at a good price. This one has 2 x HDMI.
Could a VR cause this kind of issue on a mainboard?

[BertGT]

Re: Acer AT4220 - colour/contrast problem

Hi Mikoz
I have exactly the same problem with my AT4220 TV here down under in NZ. In addition I also have a cyan coloured line down the RHS about 2 inches in.

My power board also hums a bit - so prob nothing to worry about.

If I detach the cable from the main board to the panel there's no funky colours or anything I.e. Screen is plain black with the glow of the backlight leading me to think the panel is fine as MRX pointed out above.

My thoughts are the main board is stuffed.

Did you recap the mainboard on yours?

Cheers
Bert