Dixon 42" Plasma Model STY03423D (Bad picture)

[angelos]

Hi Guys,
I have this 42" plasma with a fault that i have never seen before. Initially when i switched the TV on the first time i noticed that the "No Signal" Logo was fluctuating vertically sort of displaying it in two places simultaneously with a constant flickering. After a minute or so the picture went black except for a horizontal band at the top of about 4 inches where the picture is perfect.
The panel does not have any Voltage indication stickers so i measure my Vs = 210V and Va = 56V. I am not sure but expect the problem to be on the Y-Sus or perhaps the logic board.
Any help here would be greatly appreciated.

Regards
Angelos

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Can you post sharp focused pictures of the circuit boards and the whole back of the set to start off.

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Ok, just hold on!

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Here are the pictures.

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

It looks like only the top one or two Y buffers are working,
Have you measured all the voltages as given on the circuit boards and do they match?
I see that there is a ribbon cable coming from the left-hand and from the right-hand circuit boards but cannot see where they go.

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

The flat data ribbons you see underneath got to the logic board. I attached a picture for you to see. I will now look for voltages and check them but on which board should i focus on. The Power supply or the Y-sus board?

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

As for the voltages going to the Y-Scan panel i mentioned int er post previously the Vs and Va voltages but don't know what they should be as the panel does not indicate what they are.
The ribbon from the Y-sus board going to the logic board has a +5V rail and that is correct.
Then on the Y-sus board to PSU there is a +15V rail measuring +15.4V. No ripple were detected on these voltages using the scope.
There are not many voltage test points.
You are right the two top Y-buffer ics get slightly warm and the rest are cool to the touch indicating that they are not working. I suspect that the other buffer ic's are not getting data?
I must say that when the tv is cold to the touch and i power it up then all buffer ics work except that they cause a shaking image expect for the two top one's. Hope you understand.

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

I would look on the Yboard initially. Just check those places where voltages are given.


The picture above is of the logic board which often has several sets of pins or pads that you can short together to produce a test pattern for the screen which then isolates any problems in general with the mainboard. Unfortunately I cannot see these test points. Perhaps someone else can chip in here.

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Check the circle on the top right of the image. Those are pins like the one's you get on computer motherboards. I just dont know how to test or short them.

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Can you use freezer spray on the top two buffer IC's and will that bring back the picture?
Unfortunately I don't have very much knowledge of plasma so hopefully someone else will offer their advice.

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Check the circle on the top right of the image. Those are pins like the one's you get on computer motherboards. I just dont know how to test or short them.

Like you I think these are probably the row of pins which you short but don't know which pair. Normally people use a hard disk drive jumper to short the pins

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

There is a TP-Vsc which measure -194.6V
There are adjustments for Ramp-up, ramp down and Vscan but i would not want to adjust them as i dont know what they must be and this tv was never opened before to get tampered by someone else.

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Can you use freezer spray on the top two buffer IC's and will that bring back the picture?
Unfortunately I don't have very much knowledge of plasma so hopefully someone else will offer their advice.

I sprayed the whole lot to no effect

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Are you certain there is no label with the voltages on perhaps behind the black plastic frame.?

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

I looked everywhere. It does not have that plasma voltage label. I want to run something by you. I looked on the internet for a circuit diagram of the Y-sus and Y buffer boards to better understand how the data is communicated to the y buffer IC's but to no avail.
Obviously the logic board that sends the pixel info to the Y-SUS board must send it in either a couple of data lines or perhaps a single data line, don't know but here is the thing. On the solder side at the point where the data ribbon from the logic board connects and enter the Y-Sus board are two smd 16 pin chips and i suspect that somewhere along the line these data lines are demultiplexed and sent to the individual Y Buffer ic's and therein i believe is where the problem is. Do you have any schematics of any model plasma that shows the interaction of data between logic, ysus and y buffer?

Thanks for your assistance so far
Angelos

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

Do you have access to an oscilloscope that you could check the signal at the Ybuffers. What's the part number of the buffer IC.

[flocko]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

faulty IPM on Y sus is my bet.

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

I will check and get back to you in a couple of hours. Not at the workshop now. Yes i do have a oscilloscope. Its just awkward to measure anything as its not easy to measure on the solder side.

[angelos]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

faulty IPM on Y sus is my bet.

If you are reffering to those hybrid IC's. No this Y-Sus board uses a large heatsink with a whole lot of mosfets underneath. Remember that the first two Y Buffers are working correct. Its the other 6 that initially are flickering until they switch off and leave you with a black picture.

[dick_barton]

Re: Dixon 42" Plasma Model STY03423D (Bad picture)

This look like an interesting article.