I need help getting help, finding a replacement board, or even finding the schematic for an AOC (A42HD84) Plasma tv. I believe the main power supply board (Samsung, LJ44-00092C) is the problem.
When I got the TV there was a blown fuse on the board. See some pics of the board here:
When the board gets power there is only one voltage correctly present, all others are non-existent.
Any help or guidance anyone can provide would be greatly appreciated.
On Tue, 12 Aug 2008 11:37:37 -0700 (PDT), Chrisroberts7577 put finger to keyboard and composed:
At the risk of stating the obvious, the fact that you are getting only one voltage (the standby voltage?) suggests that your set is not coming out of standby.
One thing that strikes me straight away is that the solder joints around various coils (L465 & L466 & L341 ?) are not shiny. I usually reflow the solder at all the coils, whether good or bad.
The most obvious approach is to trace out the circuit around the blown fuse, or at least test all the active components in that area. Likely culprits would be the two MOSFETs on the adjacent heatsink which would probably be driven by the IR2109 Half-Bridge Driver IC:
Another candidate could be an open NTC resistor near the fuse. These resistors are used to limit the inrush current to the main bulk capacitor(s).
There must also be a signal (PS_ON ?) coming in via this board ...
... that switches on the main PSU. Confirm that this signal is changing state when you turn the set on, and then check to see that the output of this board is switching the AC supply.
BTW, AOC is a well known monitor manufacturer.
- Franc Zabkar
The picture you posted doesn't look like a burnt out fuse. It loooks more like an electrolytic capacitor that exploded. What does the board say in the area where you removed this component.
Mike
On Tue, 12 Aug 2008 19:39:13 -0400, "Michael Kennedy" put finger to keyboard and composed:
I thought the red component in this pic ...
... looked like one of these time delay fuses:
- Franc Zabkar
Frank thanks for your help. Here are some answers to your questions.
The TV is going from standby to the ON state fine. I've checked that small board and it seems to be doing it's job correctly. The LED on the TV changes colors when I press the on button, you hear a relay switch, and that's when the single voltage on the main board appears. The TV will not switch back into the standby state however.
I will try reflowing those solder joints tomorrow if I can remember to bring the board in to work. I was really disappointed in the quality of the board when I took a look at it. There is still flux all over it, like it never got cleaned.
I should be able to check the mosfet and resistor tonight. Hopefully I can find something.
Thanks for your input.
s e
the
Frank is correct. Luckily I found the cap of the fuse in the TV. It must have shot off when the fuse blew. So I was able to pull the p/n off of it and get a replacement for it easily (Free thanks to free samples).
-Chris
Frank is correct. Luckily I found the cap of the fuse in the TV. It must have shot off when the fuse blew. So I was able to pull the p/n off of it and get a replacement for it easily (Free thanks to free samples).
-Chris
Ah... I was just looking at the first pic. I can see that you are correct.
Mike
Have something to add? Share your thoughts — no account required.
Ask the community — no account required