Great forum here! I've learned a lot from reading these posts.
My problem is a Samsung Plasma PN42B450 which is 4 years old. About 6 months ago it started losing its picture, while sound continued. When this happens it will still respond to the remote control (volume up, down, power off, etc.), but nothing shows on the screen (not even the menu items). The only way that I have found to restore the picture is to power off, then power on. That brings back the pic, but over time it has gotten worse, such that the picture may fail 3, 4, or even 10-12 times during the first 15 - 30 minutes of operation.
Usually, it seems that after a while the TV "settles down" or "warms up" to a point that it will maintain the picture. However, don't take that to mean that it is in any way CONSISTENT with its picture failure. Far from it! During the last 10 days that I have had it opened up to try to diagnose it, there have times that I thought it should be failing when it just wouldn't.... and vice versa.
Here's what I have done so far:
1. Replaced Power Supply board. No change. (Now after reading some of the threads here, I realize that was probably foolish!)
2. Replaced Y-Main. No change.
3. Found the sticker with voltage specs. Made minor reductions in Vs and Vsc to meet specs of 205 and -195. No satisfaction. (Obviously, I did this while the set was displaying picture. Vs drops to 0 when the picture fails.)
4. Launched the test pattern by jumping pins 3 & 4 on the control board and unplugging a cable (forgot the name) to the control board (per Tom66's excellent post). Test pattern ran fine..., until the picture failed while sound continued.
I have had a POSSIBLE BREAKTHROUGH this evening that I need someone's help with: I was using the plastic handle of a screwdriver to tap gently on some of the heat sinks & boards, especially the X-Main and found that I can CAUSE a failure by tapping on the X-Main heat sink OR by tapping on the X-buffer board. I have tried to narrow it down by gently tapping individual components, but haven't had much success with that.
Would it make sense to disconnect the X-buffer from the X-Main and see if tapping the X-main still causes a failure? I didn't want to try that without asking some experts b/c I wasn't sure if it was safe to power up the TV with the x-buffer disconnected from the x-main.
I would greatly appreciate any expert guidance I could get at this point.
My problem is a Samsung Plasma PN42B450 which is 4 years old. About 6 months ago it started losing its picture, while sound continued. When this happens it will still respond to the remote control (volume up, down, power off, etc.), but nothing shows on the screen (not even the menu items). The only way that I have found to restore the picture is to power off, then power on. That brings back the pic, but over time it has gotten worse, such that the picture may fail 3, 4, or even 10-12 times during the first 15 - 30 minutes of operation.
Usually, it seems that after a while the TV "settles down" or "warms up" to a point that it will maintain the picture. However, don't take that to mean that it is in any way CONSISTENT with its picture failure. Far from it! During the last 10 days that I have had it opened up to try to diagnose it, there have times that I thought it should be failing when it just wouldn't.... and vice versa.
Here's what I have done so far:
1. Replaced Power Supply board. No change. (Now after reading some of the threads here, I realize that was probably foolish!)
2. Replaced Y-Main. No change.
3. Found the sticker with voltage specs. Made minor reductions in Vs and Vsc to meet specs of 205 and -195. No satisfaction. (Obviously, I did this while the set was displaying picture. Vs drops to 0 when the picture fails.)
4. Launched the test pattern by jumping pins 3 & 4 on the control board and unplugging a cable (forgot the name) to the control board (per Tom66's excellent post). Test pattern ran fine..., until the picture failed while sound continued.
I have had a POSSIBLE BREAKTHROUGH this evening that I need someone's help with: I was using the plastic handle of a screwdriver to tap gently on some of the heat sinks & boards, especially the X-Main and found that I can CAUSE a failure by tapping on the X-Main heat sink OR by tapping on the X-buffer board. I have tried to narrow it down by gently tapping individual components, but haven't had much success with that.
Would it make sense to disconnect the X-buffer from the X-Main and see if tapping the X-main still causes a failure? I didn't want to try that without asking some experts b/c I wasn't sure if it was safe to power up the TV with the x-buffer disconnected from the x-main.
I would greatly appreciate any expert guidance I could get at this point.
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