1966 GE PortaColor Restoration

[old_coot88]

According to Sams there should be solid continuity (zero ohms) from pin 3 of the flyback to the Height control. Since there's only 250V at the Ht control, find out where the open is. That .1 cap is not a problem if you already replaced it.

Also see if there's Boost at the screen controls. As jr_tech mentioned, if it's low it will knock the brightness down.

[jr_tech]

WAG.... the wire/run between the HV cage and circuit board that carries the 670v boost voltage to the screen and height pots is broken or cold soldered... the 250 volts measured on the height pot is actually from the 270 volt supply back feeding through the screen pots.

jr

[old_coot88]

So... if indeed there's no Boost at the scr. controls, turn all 3 down to minimum before the Boost is restored to them. Otherwise, the CRT will be overdriven and may bloom out, an unfamiliar situation for a noob.

[Dubis7]

Okay, precautions were taken as suggested. Screen controls were minimized before I started poking around again.

Sure enough, no boost voltage at any of them. In fact, the entire boost line on the PCB was dead.

So I checked the wire. Wire was good, but there was no continuity to the board.

It turns out that the same solder joint for the wire linking to pin 3 on T4 is also used for the connection to the .1uf boost capacitor, which I replaced. Apparently when I did that, the solder didn't flow properly around the boost supply wire and left it essentially hanging in midair. It was hard to spot, but when I was actually looking for problems at that joint, it was obvious that the solder had pooled around it and wasn't actually connecting.

Moreover, I've identified the source of that HV sparking, and it wasn't the flyback. As soon as I pulled the board out, I saw sparks shooting from that solder joint. Apparently they were jumping between the gap and periodically supplying boost voltage, which explains why the picture kept filling out.

So anyway, I resoldered that joint. And sure enough, I have full deflection again!

Now I can focus on a few other issues. The color sounds like it won't be hard to tackle, and I'll plan to focus on that next since I have the board loosened and accessible.

I'm also still concerned about the brightness. It seems like the picture goes completely dark for a significant portion of the control. Not as much now that boost has been restored, but still more than I'd like. Maybe that's the nature of these sets? Or does that sound like a tired CRT? I don't have a tester with me, but should I start keeping an eye out for a replacement?

Now that boost is restored, an old issue has come back. I'm noticing those flashes of bright light again, and they aren't impacted by the brightness.

I've taken a video of the progress at this point. I'd like to fix the color next, but I also made sure to capture the flashes so you can see what I'm talking about. Any thoughts on what that might could be?

Here's the video: https://youtu.be/LEAJsa0N-FU

[damen]

That type of flashing was usually caused by a defective video output tube. Will not show up in a checker, only way to tell for sure will be to sub the tube.

[old_coot88]

Tap the tubes gingerly with something like a screwdriver handle. It'll usually show up any intermittencies. Tap around on the board too. The 'tap test' was an integral part of troubleshooting back in the day.

Temporarily disconnect anything from the ant. input just to be sure that flashing isn't 'hitchhiking' in from outside the set.