1966 GE PortaColor Restoration

[jr_tech]

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

jr

[Dubis7]

Originally Posted by jr_tech

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.

[Dubis7]

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?

[Dubis7]

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?

[jr_tech]

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

jr

[Dubis7]

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.

[jr_tech]

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



jr

[Dubis7]

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.

[zeno]

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
LFOD !

[Dubis7]

Originally Posted by zeno

Just check for AC ( to GND) on both sides of C1.

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

[Dubis7]

Originally Posted by Dubis7

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.

[jr_tech]

Originally Posted by Dubis7

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

[Dubis7]

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.

[Dubis7]

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.

[damen]

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.