RCA 42PA30RQ Has sound, no picture

[NickLoC]

Have a tv I'm working on. Powers on fine. Only shows random dots, not a whole picture. Does that for 30 sec or so then fades, no picture at all. TV stays on. Have seen on this board that may need to replace multiple boards. I would like to avoid replacing random boards. Here are some pics of the boards and what the tv does. I understand this is a Samsung that is notorious for issues like this. Power supply outputs are normal.

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

I've never seen that before on one of these TVs. I'd try a couple things:

- Check the solder joints on the X-main
- Try to run a test on the logic control board: https://www.badcaps.net/forum/showth...+control+board

[tom66]

Re: RCA 42PA30RQ Has sound, no picture

Check Vsc, Vs, Ve, and Va voltages

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Where are the test point for those voltages? Tested the main outputs on the power supply. Could the logic board cause this issue?

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

Power Supply: VS and VA - can't see test points on the board - just check voltages at the connector
Y-Main: VSC is also called Vscan - location R5062
X-Main: VE test point is near main connector

Did you run the logic board test I mentioned in my previous post?

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Haven't tried the test yet. Will have to take apart. What will it show on the screen? Lines like a grid test pattern?

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

Test patterns example: http://www.justanswer.com/tv-repair/...y-picture.html

[Mrx3750]

Re: RCA 42PA30RQ Has sound, no picture

The only time I've seen dots like that on an LCD TV was when using a defective HDMI cable. I wonder if there's a bad connection somewhere in the video circuitry?

[tom66]

Re: RCA 42PA30RQ Has sound, no picture

That probably wouldn't affect the "HDMI1" display etc though

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Tried the test on the board. Got nothing on the screen at all. Which is the LVDS cable ? my board looks different. What board does the LVDS cable go to?

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

LVDS goes from the main board (board with all the inputs) to the logic board.

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Ok. Tried test again, still nothing on screen. Everything plugged in I get the dots. Tested voltages again. VE is 3.5 volt on x-main. That is with positive probe on ve and negative on grounded screw holding board down. VSC on Y-main starts at -150 and drops to 5. That is with positive probe on vscan test point and negative on ground screw holding board down. VA connector the D15v has 15 volt, the VA has 55 then drops to 0, the 2 VS start at about 212 volt and drop to 0. The VS has no header connector or wire, just solder pads. The D15v has 15 and the 2 VS start at 212 and drop to 5v as well. Seems like I have a bad PSU. Sound right? THinking a transformer is bad perhaps. Better to replace whole board or to try and replace componants ? Didn't notice the first time I tested because the 15v tested fine but the other points had no voltage listed and it droped to 5v quickly.

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

You don't necessarily have a bad PSU. You might have a bad main (X or Y), though, if you're only getting 3.5 volts from VE. Does the VE ever start out higher? What's the spec for VSC? I can't remember, and it's hard to see in your pic.

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

VSC starts out high then drops. Could bad x-main and Y-main cause voltage drop from PSU board? Can I Turn on the TV and check voltage with x-main and y main disconnected?

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

You might be able to disconnect the sustains and check the PSU on this model. I know some of these Samsungs will shut down if they detect a missing board.

I did some cross referencing on Shopjimmy.com using the Y-main and X-main, and I came up with the Samsung PN42C450B1D as a consistent match. Here's a link to some service tips from Tom's database: http://www.toms-service-manuals.com/...&Search=Submit

Edit: The similarities between the Samsung and Insignia may end with the sustain boards.

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Disconnected x-main and y-main. PSU started at 208volt and then dropped to 0v. Think I made things worse. After testing I get nothing on screen. Test procedure said to wait till voltage dropped to 10v before plugging back in. Thought I did but I got a small spark when connecting the ymain the the x-main. Ouch. Although those boards were probably at fault to begin with? Hard to tell. The PDF manual said the tv will shut down the high voltage if the x-main or ymain is disconnected

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

Ok, I would recommend pulling your Y-main and X-main to see if you have any shorted components on the heat sinks. If you find a short, that particular board will have to be replaced; component-level repair is HIGHLY inadvisable on this TV.

https://www.badcaps.net/forum/showpo...2&postcount=11

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Thanks for the info. Replaced both X-main and Y-main. TV works great now. Interesting thing is the TV was made in 2010 but the boards I pulled were a 2001 revision number. The new boards, same model number were from 2009. There were differences in components. Hopefully these are designed better. Why is it so hard on these TVs to do component level repair?

[capkid]

Re: RCA 42PA30RQ Has sound, no picture

Some of the surface mount components fail, and it's not easy to find the faulty components or to source them. Also, the through-hole transistors that fail may not be easily obtained in some cases. I went through a couple sets of components on my first couple attempts at repairing Y-main and X-main problems with these TVs. IMHO, it's not very cost effective to try a component-level repair.

Edit: You may need to do a firmware update on your TV. Check RCA's site to see if there's one available.

[NickLoC]

Re: RCA 42PA30RQ Has sound, no picture

Do you know a good source for firmware and software updates for different TVs? Some manufacturers do not post them.