RCA 42PA30RQ Sound but no picture

[Viz]

Was watching but as soon as pressing volumn control (remote) there was a pop in the back of unit and picture disappeared. No odor. Sound is fine. Sometime there are white dots (coarse 'snow') on the left (mostly upper-left) side. No heat.

Unit starts with the usual double-click. Inside label: Samsung S42AX-YB09 manufactured May 2012

Don't see anything that looks burnt/'popped'

Power supply: 15.4, 5.2, 3.3 (vs), 0 (va) [ no video signal applied ] Not finding any high voltages.

Looks like the power supply, but hey, stranger things have happened. Don't have spec sheets but 'think' that: vs=200 and va=50

Any suggested suppliers for these?

Suggested further testing before purchasing?

Thanks

[Viz]

Re: RCA 42PA30RQ Sound but no picture

Supply part # RF09231-20120517


Note: Disconnected power to Y-main. Upon startup, vs is over 200 but then drifts down to nothing.

[tom66]

Re: RCA 42PA30RQ Sound but no picture

These sets will (rather annoyingly) shut down Vs and Va after a couple of seconds if the Y-main is not detected.

You will have to remove the boards individually and check for short circuits.

I believe the buffer board does occasionally fail on these so be aware of that possibility.

[Viz]

Re: RCA 42PA30RQ Sound but no picture

Thank you

Yes, Vs is 207 for about 1 sec then fades away. However Va is always absent - floating near zero. Since only 1 connector has these two voltages and the connector is removed, then ether Va is dead on the supply or it doesn't come alive unless told to do so (and it isn't being told).

The 'logic main' pcb has a green led that flashes on for 2 seconds then off for 1 second.

In your tutorial you mention Y and/or Z boards usually being suspect on blank screen. In a link provided [ http://www.shopjimmy.com/catalogsear...lt/?q=42pa30rq ] the Y-main board states that firmware upgrade is required after installation. What is that and how does one do it? Please bear with me as this is my first plasma/flatscreen repair.

[Viz]

Re: RCA 42PA30RQ Sound but no picture

My bad: Vs=207 and Va=55 for 2 seconds then fades to zero. Doesn't matter if Y+X boards are connected. PSU probably fine. Also, no shorts for Vs or Va.

Definately a bad Y sustain. While there is nothing visable to see, it fails testing. It has 8 ics (shift registers??) connected to 6 ribbon connections. The 2nd connector (and IC)from bottom has shorts to ground. The position corrosponds to the visual portion of the screen where the volume level is shown. It failed when pressing volume on remote ... so it looks like that was the perfect storm (in a imperfect TV).

Can't find shorts or visible problem with Y-main. Any suggested further testing methods for this? (and for X-main?)

Also, does anyone know the codes for the locic-main LED?

Thanks

[tom66]

Re: RCA 42PA30RQ Sound but no picture

Not sure if I understand you, but you're saying the buffer ICs are shorted? The ones on the Y-buffer board?

[Viz]

Re: RCA 42PA30RQ Sound but no picture

Sorry, seem to be getting the wrong terminology.

Removed Y scan drive board [ LJ92-01739A ]. Set meter on ohms. Black lead on board ground. Then test each (and every) ribbon connecter pin (several hundred). About a dozen pins are < 1 ohm (shorted) -- all foils are to U5506.

Barring anything else is wrong, it is just that chip. I don't have equipment to desolder it. Would like to remove it and then test panel with the one ribbon not connected. It would demonstrate if Y-main is fine (just a big blank bar in the lower screen).

Is it safe/possible to test this way? Or does the 'protection circuitry' shut down if a ribbon isn't connected? (or worse does it go boom-boom?)

Again, thank you for your input

[tom66]

Re: RCA 42PA30RQ Sound but no picture

It will operate without that chip but anything below it will not appear on the display as the data is chained from the top to the bottom.

[Viz]

Re: RCA 42PA30RQ Sound but no picture

That makes sense. Now to figure out how to remove the chip cleanly ... my iron may be too small but my torch for HVAC brazing is too hot

Is there a possibility the panel itself caused the chip to blow? Is there a way to test panel lines (or are do they just go safely blank?)

[Viz]

Re: RCA 42PA30RQ Sound but no picture

Well, since didn't have a way to remove the chip, used a razor blade to cut and scrap off the pins. Now have a TV with 2/3 a picture - but who needs to see the sub-titles anyway.

Too bad I didn't have the tools to replace that sort of chip. Will order a replacement board for ~$30 and it should work ... then time to celebrate

Still I pose the question: Are there things that can go wrong with the panel itself that can cause this sort of failure? (beside having a Wii thrown at it) Seems they just have lines that fail but not causing catasrophic damage. Would hate to have another scan board fry - $30 is a terrible thing to waste.

Thanks tom66 for your help

[tom66]

Re: RCA 42PA30RQ Sound but no picture

Yes, panel faults can cause this problem but they are very rare, and I don't think they affect this model.
Be careful with replacement boards: they can be bad if pulled from a cracked screen.
TEST first: https://www.youtube.com/watch?v=51SZsfH60EY

If it is bad DO NOT INSTALL IT, as it can damage the Y-main board! Send it back for a refund.
(You were lucky it did not break your current Y-main, but if it fails differently it could cause damage.)

[unboltedoak]

Re: RCA 42PA30RQ Sound but no picture

Im having the same issue but when i turn the tv on it gives me one click instead of multiple clicks like other people are saying. Any help?

[Viz]

Re: RCA 42PA30RQ Sound but no picture

tom66,

Multiple thanks for the help. Got the new board, checked the pins (as per video), and installed. Works fine now.


unboltedoak,

I am not an expert but followed various posts on this forum. Noticed a number of multiple clicking posts. My set just has a double-click at the start (too much Microsoft Windows perhaps ...) which is normal for it.

1st, visually inspect for any blown/burnt components and/or bulging caps. The principle boards of interest are: PSU, Y-main, Y-scan, and X-scan. If you see something, proceed accordingly.

2nd, check your power supply (PSU). Vs should be ~207 for couple seconds. Va should be ~53 for a couple seconds. Apparently the supply shuts down the high voltages when detecting a problem - 'protection mode'. It you get these two voltages at startup, then this board is probably fine. [ There should also be 15.2 and 5.2 volts on the board -- these are probably good otherwise you wouldn't have sound. ]

Try this measurement with the power connector unconnected and then with it connected (it is a ribbon cable from the power supply to the Y-main). You can see a pin reference 'table' printed on the Y-main.

3rd, disconnect the Y-scan and test as per above video. If there is a short in chip, remove the chip (if you have a means to do so).

If it isn't the top chip, you can put the board back after removing the chip, connect the top ribbon and test. If the Y-main is good, you'll get an image at the top 1/6th of your screen.

If it is the top chip, then you can't test the Y-main this way.

From what has been posted, usually the Y-main board is bad with the Sound-but-no-picture scenario. Usually the Y-scan also has a shorted/blown chip. Occationally the X-main is also bad.

4th, check elsewhere on the forum. I can't answer because my problem was resolved with the above steps.

Wish you success in fixing the problem

[unboltedoak]

Re: RCA 42PA30RQ Sound but no picture

What board did you replace on your tv Viz?

[Viz]

Re: RCA 42PA30RQ Sound but no picture

What board did you replace on your tv Viz?

Y-scan board [ The above video calls it a Y-buffer board ]

[unboltedoak]

Re: RCA 42PA30RQ Sound but no picture

I was able to fix it. I bought x board y board and y scan drive. replaced the y scan drive and works perfectly now.

[Viz]

Re: RCA 42PA30RQ Sound but no picture

I was able to fix it. I bought x board y board and y scan drive. replaced the y scan drive and works perfectly now.

Great, another y-scan-only-to-fix!