Samsung PN43f4550AFXZA plasma HELP!

[linksys1127]

Need some guidance from the experts here. This is the second Samsung plasma that I've received with the same symptoms. The color bars show the worst of the condition. There is also image retention as well. All voltages are within .2v of the panel label. I have checked all the FET's on the heatsinks and surface mounts as well as diodes. No issues. I also have inspected all boards with a magnifying lens and bright light and have found nothing obvious. I've also cooled and heated all three boards with a hair dryer and cooling spray with no results. This model has a combo Y-main and buffer board, a power supply/ X-main combo board and a combo main/ logic board. I don't have a oscilloscope but have a in circuit ESD cap tester on the way. I'm wondering if this is the symptom of a bad panel? Any suggestions would be greatly appreciated.

Kevin

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

I’ve turned VS, VA AND VSCAN pots to try to improve things. Didn’t change things much. Tried disconnecting the y-main buffer panel flat connectors one at a time and didn’t change anything. Also did a test for each buffer IC with a meter and no shorts were found. Anyone have one of these Samsungs with this condition? I even removed the FETs and diodes attached to the heat sink on the y-main and tested in diode mode. No defects found. What should I try next? Thanks, Kevin

[hama]

Re: Samsung PN43f4550AFXZA plasma HELP!

verify R4022 IN POWER BOARD NORMALY 33ohm

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

I'll check it this evening. Thank you for your reply!

Kevin

[R_J]

Re: Samsung PN43f4550AFXZA plasma HELP!

Also check the SVT_XOUT voltage. The fault does look like a Xsus problem but could also be with the Ysus. It won't be a buffer ic issue.
I see shopjimmy has the power/x board, but is out of stock on the Y-main which "might" suggest the fault is on the Y-main.

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

I will check SVT_XOUT voltage on the X-Main as well as the resistors on the power supply board and report back. Shopjimmy being out of the Y-Main sounds like that might be the offender. Would like to find the part on the board that's causing the problem to help the next person with this issue if it doesn't turn out to be the panel. Thank you folks for help!

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

I couldn't find resistor R4022. I checked the resistors that we're close to 33 ohm. They are labeled RM897 and RM898. They both read read 36 ohms. I've included a picture from shopjimmy of the power supply board with those resistors circled. The picture is much clearer that what I can take in my garage. I also put the test pattern with the color bars in service mode and SVT_XOUT was a steady 71v DC. Thank you for help!
Kevin

[R_J]

Re: Samsung PN43f4550AFXZA plasma HELP!

Is there a Ve voltage listed on the panel label? I think SVT_XOUT of 71 volts is about right

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

Here's a picture of the panel label. I couldn't find any VE test point or anything marked VE on any plug. All other voltages listed on the label are within .2v. Thanks, Kevin

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

Has anyone seen this defect on any other plasma? What was the fix? I'm still thinking I've got a bad panel. I've taken the frame off from around the glass and throughly inspected for any defects with a strong light. None found. I've also heated and cooled the areas where the flat cables go into the panel with no change. I took two pictures of test patterns with the tv in the service mode. The first one definitely shows the defect on the lines going left to right not vertically. The second shows the defect along with the image retention I've got. Maybe these are some clues for the experts out there. I'm far from it! Thanks for looking. Kevin

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

I removed the IGBTs on the Y-main board attached to the heatsink and tested each to make sure they switch on and off with the meter in the diode mode. They did. I also tested the diodes attached to the heatsink with the IGBTs removed to isolate. They tested normally in the diode mode. Reattached the IGBTs and touched up all the solder joints on the heatsink as well as the transformer and coils. No help. Kevin

[linksys1127]

Re: Samsung PN43f4550AFXZA plasma HELP!

Today I’m going to leave it powered up and let it run for awhile. Test the FET’s with a temp gun and see if anything is heating up beyond the temps of the others or not heating up at all. Kevin