25" K7000 Vertical Oscillation/Foldover And Super Hot IC3 Repair

zenomorp

Well-known member

Donor 2015
Joined
Apr 5, 2008
Messages
9,062
Reaction score
3,935
Location
Wichita, Kansas
25" K7000. Severe vertical oscillation (only at the bottom of the screen) and the image starts folding over, losing sync, and going crazy after a minute or so (the IC3 heat sink gets scalding hot at this point). The story with this is the chassis had vertical deflection issues and the original owner changed the IC. Unfortunately, they installed the incorrect one (I don't have the information on which one it was), and the person who sent this to me installed the correct one for this application (this revision of the K7000 needs the LA7833 as opposed to an LA7831 or an AN5521). That brought the deflection back but it had the oscillation and overheating issue.

It was sent to me and I discovered that the C52 poly cap was installed in the incorrect configuration. It was installed across pins 1 and 2 instead of pins 1 and 4. It was filtering the output instead of the input. That was causing all the issues. Moved the leg over to pin 4 and it's good to go now. Just wanted to post this in case anyone has this issue or sees it in the future. If you're using an LA7833, C52 needs to be in pins 1 and 4, not pins 1 and 2.
 

Attachments

  • 1.JPG
    1.JPG
    272.8 KB · Views: 6
  • 2.JPG
    2.JPG
    270.1 KB · Views: 10
  • 3.JPG
    3.JPG
    351.9 KB · Views: 11
  • 4.JPG
    4.JPG
    320.2 KB · Views: 11
  • 5.JPG
    5.JPG
    120.6 KB · Views: 11
  • 6.JPG
    6.JPG
    373.1 KB · Views: 10
25" K7000. Severe vertical oscillation (only at the bottom of the screen) and the image starts folding over, losing sync, and going crazy after a minute or so (the IC3 heat sink gets scalding hot at this point). The story with this is the chassis had vertical deflection issues and the original owner changed the IC. Unfortunately, they installed the incorrect one (I don't have the information on which one it was), and the person who sent this to me installed the correct one for this application (this revision of the K7000 needs the LA7833 as opposed to an LA7831 or an AN5521). That brought the deflection back but it had the oscillation and overheating issue.

It was sent to me and I discovered that the C52 poly cap was installed in the incorrect configuration. It was installed across pins 1 and 2 instead of pins 1 and 4. It was filtering the output instead of the input. That was causing all the issues. Moved the leg over to pin 4 and it's good to go now. Just wanted to post this in case anyone has this issue or sees it in the future. If you're using an LA7833, C52 needs to be in pins 1 and 4, not pins 1 and 2.
was the vertical IC replaced previously? I would venture maybe you can use different ones based on where C52 is installed. I've never needed to replace a vertical IC on a K7000 before so pardon my ignorance on the topic.
 
was the vertical IC replaced previously? I would venture maybe you can use different ones based on where C52 is installed. I've never needed to replace a vertical IC on a K7000 before so pardon my ignorance on the topic.
Yes. There are traditionally three ICs that the different revisions of 7000s can use and C52 needs to be in the correct configuration depending on which IC is required.
 
Yes. There are traditionally three ICs that the different revisions of 7000s can use and C52 needs to be in the correct configuration depending on which IC is required.
I just tell people to replace with the exact part. I do the same with the voltage regulators, there are jumpers you can change there.
 
Back
Top Bottom