Porta Color HC Chassis, Severe Ringing in Picture

[Jon1967us]

This post concerns another tough dog problem in a 1967 HC chassis. Kind of scratching my head on this one. Ringing in the picture. The set will sometimes start up with a near perfect picture, and then after about 7-10 minutes show ringing in the pic. Sometimes the set will power on with ringing in pic, even after sitting for a couple hours. This symptom can sometimes be brought about by tapping on or near the set, but usually cannot be stopped by percussive force.

The ringing is NOT affected by fine tuning the channel, other than affecting the signal strength of the entire pic. It's the same symptom whether we're on channel 3 or 6. Neither is it affected by turning any of the IF coils.

Schematic:

https://i.ibb.co/0nB3JRj/GE-Portacolor-HC-Schematic.jpg

Video showing image and waveform, from input of Vid Amp/V6A, pin 11

https://www.youtube.com/watch?v=6ZTS...l=Silvertone58

Video showing image with no ringing and waveform, from input of 1st IF/V3A, pin 10

https://www.youtube.com/watch?v=EO3D...l=Silvertone58

Video showing image with ringing and waveform, from input of 1st IF/V3A, pin 10

https://www.youtube.com/watch?v=99Ox...l=Silvertone58





I have had issues with the contacts in the tuner and strips inside breaking, but I have cleaned the contacts and made sure they are contacting well. I have repaired the strips that have broken (the fine tuning slug got caught in the tuner case and jammed up the works)

• B+ (130v) on tuner and 270v on IF/video tubes measure ok.
  
• All IF and video tubes have been replaced.
  
• Both tuner tubes have been checked and substituted with no improvement.

I'm setting the scope to trigger on the main waveform, but I am seeing what looks like duplication behind the main waveform, that I would assume would be indicative of ringing, but I'm not certain.