Porta Color HC Chassis, Severe Ringing in Picture
 

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.

Since you've done a lot of work on the tuner already, check the shielded coax that carries the IF signal and see if there's a broken ground at one end. Long shot, but i've seen it cause the very issue you're having (tho not on a GE).

I did check the coax from tuner to board and everything is solid. I also reflowed the solder joints for that and the IF tube socket pins. No improvement as of yet. Mechanical/percussive movement does seem to affect things, but usually momentarily.

One thing I forgot to do was to inject signal directly into the IF, which I will do shortly and report back the results.

Turned out it was a matter of a cold solder joint of the delay line.

Ran a signal through the IF stages and it still was present even going into the Vid amp.
Mechanical movement produced condition starting in the area of the Vid amp, but poking around with a chopstick in the vicinity of the delay line also affected condition. A very very difficult to see cold solder joint was found off the delay line. Possibly someone trimmed this lead too closely at the factory.

Still have a little bit of intermittent color shift, possibly made more apparent just by reflowing the solder joints, and regaining full function of the delay line. Still a bit of work to do, but the set is very watchable now.

The boards in these things are thin and quite prone to faults due to set movement and heat. Honestly, the whole board needs to be gone over with a fine tooth comb.

I have a HD model. There is a world of difference between the HC and HD.
The HD has the finer dot pattern CRT, but still a low focus type. Different tubes in sweep and HV rectifier.

Nice work finding the problem. In the day we had a few
delay lines causing similar problems but I never thought of it.
Goes to show the pay off tracing & injecting can do to narrow things
down to a block in jig time.
Great sticktoitiveness.

73 Zeno:smoke:
LFOD !

I'm not familiar with the HD chassis, but I have an H3 and, yes, the contrast and dot pattern is better, but then, along comes the later HE chassis, and the dot pattern becomes big again.

These kinds of problems, ringing and smearing can be very tough to isolate. Good old Sencore VA-48 really came through, with it's ability to inject differen't types of IF signals. Chopsticks are swell too.