1966 GE PortaColor Restoration - Page 12 - Videokarma.org TV - Video

user181 · #**166** 03-20-2020, 05:17 PM

What part did you have 3D printed? Do you have a picture?

Dubis7 · #**167** 08-02-2022, 07:32 PM

So this has been awhile.

As far as the 3D printing goes - it's not that exciting of a part. One of the slats on the back had broken off and I had it replaced and glued in. Looks much better now.

That being said...

My set has had a relapse. It's been working fairly well for the past few years since restoration. No serious complaints, save for some bad buzzing when I use my Atari 2600 on it which I think is due to the signal strength and not all that fixable. I've never quite gotten the balance right on the quadrature coil for that.

However, a few weeks ago the color went out. It still has audio and an image, but it's completely black and white.

I'm not entirely sure where to start, save for replacing a few of the tubes in the color section. I'm thinking of maybe trying a new Chroma Amp, but that would just be fumbling in the dark. Does anyone have any guidance on where I could start looking?

Dubis7 · #**168** 08-04-2022, 04:00 PM

Ok I've at least isolated the problem to a specific area. Pin 2 of the 8BQ11 Chroma Amp should be around 200V. I'm reading around 180V between it and ground. Willing to bet that tube is weak. I have a new one on the way to confirm, and short of that I'll check the circuit around it.

The problem must be there, though. Luma video displays with no issues, and I've got audio, so anything up through the 11BT11 has to be fine. If the tube itself isn't the issue I'll see if R84 or R85 have gone bad.

Dubis7 · #**169** 08-05-2022, 10:07 AM

Tested tube voltages for the 8BQ11 and 8BU11:

8BQ11: Pin 2 reads around 180V, as does pin 3. These should both read around 200V, so perhaps this tube is weak? I'm surprised I'm getting no color, though, these don't seem low enough to totally kill my color.

8BU11: Pin 9 reads around 130V. Pin 10 reads around 230V and pin 3 reads around 220V. Again, these seem in line with what should be expected voltage wise.

I'm going to confirm that I have around 170V on pins 2, 5 and 10 of the 6AC10. Those appear to be the final point of contact for the red, green and blue color signals before they hit the CRT. It could be that something has shorted in that tube and killed my color signals. If that's not the case, I'll check R84 and R85 to confirm they haven't shorted and then start working backwards from the 6AC10 to find where my signal is dying.

Dubis7 · #**170** 08-06-2022, 03:51 PM

Hey, so any help here would be appreciated. I need some guidance on how I can go about testing this next component.

I've discovered that the SAMS numbers don't line up with the numbers stamped on the bottom of the Portacolor. that's going to make this much more difficult to test at the component level when I'm working from the underside. Does anyone know if there's a rhyme or reason to match them up?

Second point: I'm almost certain my problem is related to the ringing color circuit. It was previously called "infamous" which I assume means this is a common source of trouble. My tube outputs all have the correct voltages, or at least in range, and replacing both the Chroma and Color amps had no impact.

So here's what I'm thinking: knowing that my burst gate signal is present (or at least operating at the right voltage), and pin 10 of the 8BU11 is still outputting a voltage in a tolerable range, my problem is likely to be either:

1. The crystal
2. The 2.4 pf capacitor marked at C80 on the SAMS schematic
3. The 220 ohm resistor marked as R93 on the SAMS schematic.

I have no means of testing the crystal, but Moyers has the part so I'll plan to test the other two and, if those are fine, I'll replace it.

Here's the thing, though. While I've identified R93 on the top of the schematic, it looks like the crystal is buried under a shield which in turn is blocked from the underside by the plastic support running down the center. So that's my second question: Are there any tricks to getting at this thing, or do I need to tear this down further to pull the whole unit apart?

Again, I'd be incredibly appreciative of any help here. I'm eager to get this working and I've made serious progress in figuring out where the problem ISN'T, but I want to make sure that as I get further into the weeds here I'm not doing anything that would damage any parts.

Dubis7 · #**171** 05-12-2023, 12:18 PM

Realized I never updated this thread - the portacolor is working once more. I can't tell you exactly what was wrong, I fiddled around underneath for awhile, swapped the crystal and discovered that the pinout was different, swapped it back to the original and the color was back.

I had also touched up a few solder joints around the tube sockets while I was down there. It's been stable since so without having actually replaced any parts I'll suppose that there was an intermittent cold solder joint somewhere that I caught. Unless it comes back.

kf4rca · #**172** 05-16-2023, 07:16 AM

How about some pictures?

Dubis7 · #**173** 05-25-2023, 12:53 PM

Photos are a bit too big to share but here's the set!

https://imgur.com/a/7M38RXn

kf4rca · #**174** 05-26-2023, 06:22 AM

That's a pretty one. The top isn't all scratched up. You should round up as many spare parts as you can especially those compactrons!
Yeah, I've had trouble posting pics here. Probably be going to imgur myself!

dieseljeep · #**175** 05-26-2023, 08:27 AM

Quote:

Originally Posted by kf4rca

That's a pretty one. The top isn't all scratched up. You should round up as many spare parts as you can especially those compactrons!
Yeah, I've had trouble posting pics here. Probably be going to imgur myself!

I got a lot of the tubes needed for my PortaColors from ESRC. RIP, Stan!

Electronic M · #**176** 05-26-2023, 12:40 PM

Quote:

Originally Posted by kf4rca

That's a pretty one. The top isn't all scratched up. You should round up as many spare parts as you can especially those compactrons!
Yeah, I've had trouble posting pics here. Probably be going to imgur myself!

Flickr is better in that you can seemlessly embed pictures into the text.

It honestly annoys me whenever I have to read a post with imgur and have to click links to view pictures...Makes the threads look blander too.

Dubis7 · #**177** 05-28-2023, 07:00 PM

Quote:

Originally Posted by Electronic M

Flickr is better in that you can seemlessly embed pictures into the text.

Oh cool, I'll give that a try next time! I just upgraded my phone after about 6 years with the old one - I think the default size has gotten too big for the native image sharing setup.

I only wish I could get this to behave a little better with strong signals. Try as I might I've never managed to get rid of the loud buzzing that comes up during colorful segments by fiddling with the internal controls or my transmitter setup. I suppose it's the nature of these beasts, especially with Portacolors as they are.

Electronic M · #**178** 05-29-2023, 12:02 PM

Quote:

Originally Posted by Dubis7

Oh cool, I'll give that a try next time! I just upgraded my phone after about 6 years with the old one - I think the default size has gotten too big for the native image sharing setup.

I only wish I could get this to behave a little better with strong signals. Try as I might I've never managed to get rid of the loud buzzing that comes up during colorful segments by fiddling with the internal controls or my transmitter setup. I suppose it's the nature of these beasts, especially with Portacolors as they are.

A few months ago the default max image upload size/sites ability to auto rescale got messed with in a server maintenance session and it hasn't been fixed. I've had the same phone since last summer and I can remember when uploads stopped working after the maintenance. I'm almost out of storage on VK anyway so I plan to go back to flicker (which was my go-to after Photobucket imploded and before I had a smartphone.