1966 GE PortaColor Restoration

[damen]

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.

[Dubis7]

Originally Posted by damen

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.

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.

[Dubis7]

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.

[Dubis7]

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.

[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]

I may have something here.

I'm noticing that my voltages are consistently 10 or so volts higher, except the HV which is several KV too low. I traced it back, and discovered that C103 has 0 volts when measured against ground.

I've ordered a replacement. Could that be related to my issue?

[Dubis7]

Also, if L34 is measuring 36 ohms, could that be an issue?

[jr_tech]

Originally Posted by Dubis7

Also, if L34 is measuring 36 ohms, could that be an issue?

No.

Also re-check your C-103 reading, it can’t be 0 volts, if it is wired correctly and supplies are normal (or slightly high).

What does your boost voltage measure?

jr

[jr_tech]

Link to schematic from the first post of this thread:

https://drive.google.com/file/d/1q4d...aMPiHQKBL/view

jr