1966 GE PortaColor Restoration
 

Hi all,

I'm in the midst of restoring a 1966 GE Portacolor and was hoping for some guidance. In replacing one of the can capacitors, I screwed up and installed one of the sections backwards. Now it's gone from mostly working to lighting the tube heaters and doing nothing else.

According to the schematic, there's a .5V fuse just before the capacitor I installed backwards. That would trip if someone did what I did, and would cause the symptoms I've seen. I see it on the tube chart, I see it listed multiple times in the schematic, but I'll be damned if I can see it in the set.

I'm including the schematic. Has anyone worked on one of these before? I'm trying to find fuse M2. Am I losing my mind or something?

https://drive.google.com/file/d/1q4d...ew?usp=sharing

It is shown on the bottom left hand corner of the "printed circuit - top view" diagram, which is the image on the right hand side of page 8.

Find L34, and trace it out - one wire should go to a rectifier diode, the other to fuse M2.

Also, this may not be a normal glass fuse.. sometimes TV sets (no idea about this one) used a hair thin piece of wire as a fuse. If this is the case, put in a normal AGC fuse holder and install a normal 1/2 amp fuse.

That might be worth checking. I'll see if that's the case here. Thanks.

Okay, I traced the two ends of L34 and haven't had any luck. Everything has continuity so far. Any other direction?

Luck with what? What has continuity? Are you getting B+ when the set is on?

Many times the GE factory literature would dedicate an entire page to "production changes" using a code number generally ink stamped on some large metal part of the chassis,usually 3 digits. Fuses added, fuses removed, resistor/cap values changed. Which section of the cap was mis-wired? (C what?). Will have to back track from that point.

Sorry, should've been clearer. In tracing the line between L34 and the associated 100uF cap, there are no visible fuses and everything has continuity. All the diodes test good, and I run continuity tests on all the wires to see if one of them was meant to work as a fuse. If they are, then none are broken.

Right now the cord is locked into the back of the cabinet, so I haven't been able to run any tests to see where the B+ breakdown is. I'm going to guess I don't, though, since there's no life beyond the filament string. My next step is going to be freeing that cord so I can start doing voltage checks with the set on.

You know, I should check that. I know which cap it was and have since corrected the orientation, but since the schematic showed a fuse there I assumed it was C2-B. However, now that you mention that and I'm actually taking a step back, I think it was C2-D. I'm checking for where that is on the schematic now, and I can also check directly on the unit either late tomorrow or Wednesday.

I was always taught to make diagrams on a piece of paper when changing out a multican capacitor but I suppose in this modern electronic day we all live in a picture taken on a phone is just as good to do too.

The power cord interlock connector is held by a "C" clip, easy to remove. It's the earlier PortaColor chassis.
IIRC, The set has two power supplies, one half wave 140 volt source and one 240 volt, voltage doubler source. It has three power supply diodes and maybe two wire-wound resistors. The power supply is near the HV enclosure and there should be a fuse nearby, as well. :scratch2:

1966 Porta-Color ?!? Could be a very early example. I THINK they introduced these things in fall '65 for the '66 season. My Dad always said he got the 1st one in NE Tennessee, he loved being the 1st one w/a new toy like that. Also, the rather decrepit Zenith 24" B/W we had FINALLY went Ker-Pop! & died.. The little Porta-Potty took up about a 10th of the room, the old battleaxe did, that wasn't a bad thing, either, & it was COLOR !! Whoo-Pee !

There is a resistor shown in series with the fuse. They may have eliminated the fuse & used a fusable resistor instead to save $$. If either are blown
check the 3 rectifiers.

73 Zeno:smoke:
LFOD !

The rectifiers tested good, but you may be onto something about R119. I'll give that a look the next time I'm at my workbench. It's got some insulation around it, and I wouldn't be surprised if there was something under there.

Okay, so R119 is tested and has continuity. I rechecked the diodes, all appear to behave as expected.

So now I'm looking at the connections around C2 D. It has two wires. One goes to the vertical linearity control, which I checked and it appears to be operating normally. The other goes to the circuit board, and I'm having some trouble finding that on the schematic. Perhaps there's something on the circuit board that's blown?

Still no sign of that fuse. I'm wondering if that wasn't removed on the version I have.

I also plan to pull the power cord tomorrow and do some voltage tests. Maybe that will highlight where the power is failing.

Okay, hold on.

Can someone double check C1 for me. I think I may have figured out what I did wrong.

When I removed the original C1, I directly wired M1 and a few other pieces that were connected to the negative terminal of C1 to ground, and I also connected the negative terminal of the replacement C1 directly to ground.

However, C1 was mounted through an insulating pad, and in looking at the schematic, that's not actually what's going on with it, is it? Should I rewire it to have it floating away from ground? Maybe that's the origin of this whole thing.

Bingo! the negative end of C1 shoud not be grounded. M1 is likely blown also if it was connected to ground.

jr

I'll double check, but I've repeatedly verified that M1 still had continuity. I'm thinking I got lucky here and a simple wiring fix will get me back to where I want to be.

Alright. Well, C1 is now lined up correctly and I'm still not seeing any life. The tubes are glowing brighter, for what that's worth, and I'm hearing the hum you normally hear when things are warming up, but nothing else.

So I'm gonna pull that power cord this weekend and prep for taking measurements. Any thoughts on where to start?

Am I wrong to think that M1 could still show continuity if it's in circuit? I'm starting to wonder if that isn't my problem, but I'm measuring continuity across ground instead of across the fuse when I test it. Would it be worthwhile to remove the fuse and recheck?

I would first check the three power supplies and the fuse M1 when removed.

jr

Okay, so diodes x1-x3 were removed from the circuit, tested fine, and reinstalled. M1 was also removed, checked good, and reinstalled. Still no life.

I'm looking at removing R119 and doing a continuity check across it next. This has to be early in the line.

Where would you all recommend I measure next? I have the cord out of the cabinet and I'm ready to take voltage measurements.

Are the 3 power supply (labeled source voltages) in spec?

https://live.staticflickr.com/65535/...91a18b_c_d.jpg

jr

I'm going to assume no on at least one of them. I'll plan to check them either tonight or tomorrow, depending on my schedule. I think I may also take a look at C1 again, just to see if it's got any amps going across it.

Just check for AC ( to GND) on both sides of C1. If there check the
supplies # 1, 2, & 3 for DC.
Keep in mind most the time things in Sams flow left to right.
Try to find a mid point & test voltage. Go upstream or downstream
from there.

73 Zeno:smoke:
LFOD !

Is C1 AC? I've been checking on the DC setting.

Yeah, I'm thinking C1 is DC because of where it is in relation to the diodes, but please correct me if that's wrong.

There is ac on both sides of the cap, but the output is shifted up dc wise. See video of voltage doubler circuit.

https://m.youtube.com/watch?v=Iq-5PPpVHNw

jr

Okay, I found my problem!

R119 is several million ohms. It's supposed to be 3.6 ohms. I jumped it with some alligator clips (briefly) and the TV came back to life!

So I'm going to order another R119 and get back to work on this.

Thanks for your help so far, everyone. Next step is to make sure it powers up with all that fixed, and replace C3. Hopefully that will close this whole thing down.

Hm, having some trouble with this one. Does anyone have a good source for 3.6 ohm resistors with 7 (or highter) watt ratings? Any thoughts on how flexible this part is going to be? Would a 3 ohm do it?

If I did them in series, I could get a 3 ohm and .5 ohm 10 watt resistor from JustRadios, but I'd prefer to use one part is possible.

RCA used a 3.9 ohm one in a lot of their later sets. The 7 watt part number is 143565, the 10 watt one is 153664. Going up or down 1 ohm should not cause any issues.

I would use the 3.9 ohm. Its there to reduce in rush current at
turn on so the electrolytics charge slower. It also protects the fuse
from random blowing. Most sets do not use a fuse, just the resistor.
In that case it is of a fusable design not just a wirewound resistor.

73 Zeno:smoke:
LFOD !

Whoops. I bought a 3.5 ohm at 10 watt last night. Oh well. If I decide I'm not happy with it, I can always switch over.

On the plus side, I also decided to add that missing fuse. I'm real sure GE left it out, so I've ordered one and plan to install it where the schematic calls for it. It's probably not necessary, but it will make me feel a little better.

It looks like once that part comes in I'll be able to get back to where I should be. I'll verify it's still passing video and audio and go from there. One more 3 section can to go.

Okay, well mixed news.

The new resistor (Replacing R119) fixed the power issue. I now have sound, video, and high voltage back.

Only problem: I've lost part of my vertical deflection. I also was hearing a clicking from the flyback, but I'm still getting HV and that seems to have stopped after I tightened a few screws on the HV cage. Not sure why that would fix it, but there we are.

So here's what I'm going to check:

- I'll verify that I'm getting the correct voltages out of the 3 sections of the
power supply. Perhaps they're too low.

- I'll verify my HV is high enough. Could that cause partial loss of vertical?

I know the yoke is okay, because in fiddling with the height I've been able to get the picture to bounce all the way down, but it almost immediately bounces back up.

I'm including a video as well. Perhaps someone can point me towards a suspect section?

https://youtu.be/D5siDbEAvU0

1. good

2. No, If HV is too low the picture would be bigger. (slower moving elections are easier to deflect)

3. Seems reasonable.

4. Have you tried adjusting vertical linearity?

jr

I did try this. It definitely reacted, but not enough to fill the screen.

A few more clues before I call it a night:

I'm getting a response from the brightness control. When I decrease the brightness, the flyback starts clicking like mad and fills out the screen, somewhat. It more flickers with each click. The picture does grow larger. The picture was shrinking when I increased the brightness before I started.

Also, now the flyback is ringing at me. I'm not sure what that means, or if that makes sense. I took a video of it.

I'm noticing that, when I stick a screwdriver near the flyback ring, small blue sparks jump to it. I think that's normal, but maybe not? Maybe I need to treat the flyback with some corona dope?

I decided to stop taking voltages since I wasn't sure if the ringing was dangerous. I measured two of the three sources, and noticed they were actually running about 10 VDC higher than they were supposed to. I'm not sure if that's within tolerance or not.

https://www.youtube.com/watch?v=A3hx...ature=youtu.be

You said in the first post that the tv was “mostly working” before you replaced the electrolytics. So are these new problems, perhaps associated with the rebuilding efforts or were they observed initially?

jr

They existed, but have changed, if that makes sense. When I started, the set had AC hum in the audio from bad electrolytics. The picture would shrink and change size with brightness, and the vertical hold was exceptionally touchy. I was also noticing some flashing on the screen. I'm not sure how to describe it, almost like WWII era flak, if you've ever seen video of that. With the brightness up it looked more like the flickering lines you get with tracking issues on a VCR, but with the brightness down they'd be more visible. That wouldn't start until the set had been on for awhile, though.

Since replacing C1 and C2, plus the two paper caps on the main board, the vertical and horizontal hold is much better and the audio hum is gone, but the picture shrinkage and growth is much worse, and I'm hearing sparking from around the flyback. I can't seem to find exactly where it's coming from, though, and I'm not seeing any parts actually failing. I ended up leaving it on for awhile and despite all the sparking noises nothing actually stopped working. It has developed that ringing that I posted earlier, that's new as of last night (and didn't start until quite awhile after replacing C1 and C2.)

I'm wondering if I don't have a problem with the HV rectifier. I ordered a spare to see if that changes anything. I know I have HV from the flyback, since bringing a screwdriver near it and the cap to the HV rectifier causes it to send a healthy spark, so I'm personally inclined to think that the flyback itself is fine.

Any other thoughts? Could this be a yoke problem?

If the rectifier isn't the problem the cup it's socket is in might be...I had a friend's 13" Zenith tube color on the bench a few years ago and that set had HV rect socket cup arc through....the point of the screw that held the socket in the cup was arcing through the cup to the chassis. My solution was clean the living daylight out of the cup to confirm condition, drill out the arc hole and carbon path near it, fill the drill hole with RTV silicone to block the arcing path, and shorten the screw and round it's point to avoid a relapse....worked like a charm, and hasn't failed yet.

Okay, so I'm potentially on the right track that my HV rectifier might be suspect, then? I was more or less shooting in the dark, but I figured it's a cheap part and an easy swap, and worst case I have a spare I can access.

I've heard of something called "Bloom" Does that sound similar to what I'm describing?