AOC A42HD84 42" Plasma Bad Picture

[1997eclipsegst]

Hey everyone,

I am working on a older AOC A42HD84 Plasma that turns on and works but the picture is really washed out and dim.

I have verified the proper voltages on the power supply from the panel sticker.

Checked fuses on the Y and X main and both are good.

I ran the set for 15 mins and felt the heatsinks on the Y and X main and both are warm but it seems that the X main is a bit warmer.

It seems like some of the pixels get "stuck" on certain images then return to somewhat normal (but dim and washed out) when the image changes.

Not sure what else to check?

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

Can you see a place to check the Ve, Vset and -Vsc voltages? Also check Vs on power supply directly.

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

The power supply has test points for the following and the voltages adjusted to the panel sticker specs

VA 70
VS 204
VSC -190
VE 84
Vset 195

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

Tested voltages at the connector going to the X and Y main boards

X-Main
1 VDD 5.2
2 VCC 15.0
3 GND
4 N/C
5 VE 84.0
6 N/C
7 GND
8 GND
9 N/C
10 VS 204.5
11 VS 204.5

Y-Main
This board was not labeled. Started from top to bottom

1 204.5
2 204.5
3 N/C
4 GND
5 N/C
6 195.2
7 N/C
8 GND
9 -190.2
10 GND
11 14.9
12 5.2

VA is going to the logic buffers at the bottom of the set and reads 70.2 at the buffer

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

OK, can you get a picture of the logic board? This is roughly the same as an LCD panel tcon board.

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

Picture of the logic board

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

Hmm, it does not have standard test pattern jumper position. On any of the vertical pin headers is there a pictorial indicating a mode to put them in, which they aren't already in? I suspect it may be the 3x2 header but I'm not sure.

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

I don't see anything that would indicate a mode for a test pattern.

The only thing I can see is a number 1 and 3 almost printed on top of each other. It is the same on both sides of the 3x2 header. The other header is labeled 1 thru 5

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

Picture of headers

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

Does anything happen if you press the button on the control board?

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

Tried just pressing it, holding for 5 and 10 seconds, and powering on with the button pressed and nothing happens.

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

How are the brightness/contrast settings in the user menu? Tried a factory reset? Just in case...

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

Just tried resetting picture settings to default and tried to adjust different picture settings with no improvement.

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

Do you see Yrr or Yfr adjustments on the Y-main board?

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

There are 4 adjustment pots on the Y-Main labeled
VR5001
VR5002
VR5003
VR5004
They don't have any other markings by them. I downloaded the service manual for this set and the one in the manual has completely different Y-Main and X-Main boards.

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

Can you post pictures of the general area around each?

[1997eclipsegst]

Re: AOC A42HD84 42" Plasma Bad Picture

tom66,

Sorry for the late reply. Here are a couple pictures of the Y-Main

[tom66]

Re: AOC A42HD84 42" Plasma Bad Picture

The two left of the transformer (yellow thing printed "LJ26-....") are probably the voltage adjustments, the two right are probably the timing adjustments. Try adjusting voltages to spec, if they are out by more than 3V; then adjust the timings.