GE 810 Restoration

[Crist Rigott]

Originally Posted by Yamamaya42

Sucks that it happened, esp after all you have done so far...

But I do have to ask...
Unfamiliar term...

"5U4G was pinballing!"

pinballing?
Not heard that used in relation to tubes before.

There were flashes coming from the tube.

[JohnCT]

Originally Posted by Yamamaya42

Sucks that it happened, esp after all you have done so far...

But I do have to ask...
Unfamiliar term...

"5U4G was pinballing!"

pinballing?
Not heard that used in relation to tubes before.

Take an old defective tube. Put it in the microwave for a few seconds..

John

[Kevin Kuehn]

I wouldn't suggest putting anything metallic in a microwave.

[Yamamaya42]

Originally Posted by Kevin Kuehn

I wouldn't suggest putting anything metallic in a microwave.

how about microwave plasma using the old grape trick? :p

[Boobtubeman]

AKA--- July 4th came early inside the 5U4 tube...

SR

[Crist Rigott]

I fixed the yoke! I think it was shorting out on the inner tube windings.

I used my heat gun to warm up the inner tube and slid it out of the yoke. This was a mistake. You see the inner tube has some very fine wire windings on it and when I slide the tube out, I broke the fine wire lead that was soldered to the black wire that is grounded to the chassis. You can see it in this photo where the lead is insulated with a small 1/8 long fiberglass sleeve between the 2 layers of windings.




I then continued to disassemble the yoke by separating the 2 windings. They sure liked to used that real sticky cloth tape!

When I removed the aluminum shell I saw that the windings were wrapped with a thin sheet of metal.




The next group of pictures show the disassembled yoke parts.











The next group shows the inner tube and its windings. This is where I think the short occurred. The windings are covered with a very thin plastic type of material. Well there was 1 spot that the windings were worn through and shiny copper colored. You can see this in the picture with the pencil pointing to the worn through spot. The small fine wire that I broke off is at the opposite end of the worn though spot. I peeled back the plastic and unwound about an inch of wire so it can be resoldered back the black wire lug. I then cleaned and added a layer of Kapton tape over the whole thing.








I then made a new insulating washer from an old milk jug. This helps insulate the windings from each other.




I then cleaned and reassembled the yoke. I ohmed it out and sure enough the short was gone. I reinstalled everything and replaced the 5U4G tube. The old tube has little balls of metal rolling around. Fired it back up using my variac checking the current draw. All was fine and I now have my picture back. I'm letting it "burn" in for a while.

[JohnCT]

Nice job.

Reminds me of the mid 90s Mitsubishi projection yokes (essentially B&W) that used to burn from the left horiz winding to the right. Once the yokes went out of production, it was either repair them or lose a repair job.

I used to separate the burned windings and isolate them. Covered with about 10 layers of cyanoacrylate, no more problems.

The good thing is that the burned/shorted area was external, right about where the neck and bell met, so I didn't have to disassemble the whole yoke like you had to.

Impressed.

John

[Phil Nelson]

Originally Posted by Crist Rigott

the L2 filter choke started to sizzle and spit out wax. . . I remembered reading when Phil restored his 810 he had an almost identical situation. His yoke windings has shorted together. So I checked mine. Same thing.

Yes, the burned-up filter choke and the shorted yoke -- fond memories! I was lucky enough to find replacement parts on eBay.

I also had to replace a cheap socket that failed by arcing between the pins. My 810 works well now, but I can't say I was very impressed with the overall build quality.

It's great that you were able to repair your yoke. It may outlast any of the originals out there.

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html

[old_coot88]

Originally Posted by Crist Rigott

I fixed the yoke! I think it was shorting out on the inner tube windings.

Dude. You got more guts than a Army mule.

[Tom9589]

Where is the fine wire coil that you repaired connected in the circuit? Is is in series with one of the other windings? I didn't see any separate coil shown in either the Rider or Sams schematic.

[Electronic M]

Nice work.

Once a yoke choke or transformer fails it can't be broken again till it's fixed so there's nothing to loose trying to fix it.... that approach has saved me hunting for unobtanium a few times.

[Crist Rigott]

Originally Posted by Tom9589

Where is the fine wire coil that you repaired connected in the circuit? Is is in series with one of the other windings? I didn't see any separate coil shown in either the Rider or Sams schematic.

The coil is connected to the black wire on the yoke that goes to chassis ground. The coil only had the 1 end connected. The end near the worn through spot just ends. My guess is that the coil on the tube is some sort of a shield. But I really don't know.

The coil is not shown on any schematic because it is an integral part of the yoke assembly, again my guess.

[Electronic M]

... never mind.

[Tom9589]

The idea of a shield makes sense. However, I maintain that it should have been represented in the schematic in some fashion.

[irext]

If anyone was going to fix it and make it better than new it would be you. Very nice work.