I worry a little about the epoxy. If it is the type that hardens vary hard, and it expands with heat at a different rate than the coil, it could tend to tear things apart.

ASE has a $10 min order and after I add the second can and postage I end up with two cans for more than $20. I found a local electronics supplier who has a similar product. I can pick up some other parts I need too. Thanks for all the leads though.

I do have a question since I'm in the area of the flyback. Under the 1B3GT--HV rectifier, the resistors shown in this pic aren't on the schematic. Also, why is there a ring connected between pins 7 and 8? I'm also curious about that thing to the lower left of the socket with the wire and screw.
The schematic I have is for the 23G24 chassis.

Tom, I've never used this before but it's made to withstand heat expansion acording to the manufacture.

The Epoxy spray is good for getting inside windings and sealing individual windings where the insulation is bad, ( i repaired a shorted RF type HV transformer using this method) not that much voltage difference from one winding to the next, but it's not as good at replacing the wax outer coating, (though I would spray it on before applying a new coating) I have applied Epoxy spray to the outside of a good flyback to seal it, however it will still Corona if you hold a screwdriver next to the donut so obviously it's not enough.
(unless you can spray enough on to build it up several Mils thick)

Low acid Silicon is very good for Flybacks, I redid one on a CTC7 with that stuff and it worked fine, just be sure to get the low acid type, it doesn't smell really Vinegary like the regular stuff.

You might want to take a look at this Video, a member of Videokarma (and here I think) deep fried a Flyback in Wax and then pumped it into a Vacuum to pull the Wax inside it, it worked I guess.

http://www.youtube.com/watch?v=tVK2ZoiT9uA

I think that orange-orange-gold resistor is R80(3.3 ohms) on the schematic. It's in series with the 1B3 filament.

I think the other resistor may be R77(470k?) coming off pin 7. They may be using one of the unused socket pins for a tie point. It looks like there is another wire coming off pin 7 that goes over to the 500mmf(C84) doorknob capacitor.

Eric, Deep fried flyback? Sounds like a southern treat

Here's my take on the flyback coating from what I've read, because I certainly have no experience with this. First, the epoxy coat to penetrate the coils and hopefully reseal any that might have flaws. I'm skeptical however that it will be able to penetrate all the way through the windings. I've read that there should be no air present to stop corona and or arcing. I think the epoxy will get this done well enough.

That said, I don't think acid present in the RTV would harm anything since it mostly seems to be present during the cure process. The epoxy would prevent it from getting at anything sensitive I would think. I think Phil is right about using the RTV. Acording to specs it has a 24kv/mm dielectric, which means a thin coating would work fine to prevent arcing and would be thin enough to allow heat to dissapate as well. Wax might be original but I don't think it can begin to appraoch the quality and durability of silicone.

Kevin, I see the resistors now in the schematic. Question--the doorknob cap, will that have to be replaced? If so, with what? Also, the purpose of the ring?

I really like that video, I want to try something like that, but plan to use a thick sheet of plastic, like lexan or something along that line for the top so I can observe the action while its under vacuum.

Perhaps, but I would recommend that you use the low acid RTV anyway.


The doorknob caps are usually good. Don't replace it unless it causes problems when running the set.
The ring is to prevent corona. Any sharp point or edge can cause a corona discharge. The ring shields any sharp points in the wiring at the tube socket, and it is nice and smooth itself.

Oh boy does that bring back memories. In that area, there is 12KV - 14KV - voltage that is generated and put on the anode of the CRT (i.e. all over the metal on the outside part of your CRT). Leave this area along unless you have problems. Remember, there is high voltage here along with on the outside of the CRT. You will need to watch/listen this area for arcing and hissing sounds. Note that all the solder joints are big smooth blobs of solder. Any sharp point likely will cause HV arcing. That ring around the 1B3 suppresses arcing. There is red paint like substance there - call Corona Dope - used to suppress HV arcing.

On my Porthole, the phenolic board and the 1B3 tube socket were compromised with carbon traces due to excessive arcing. I had to replace the 1B3 socket, drill out the carbon in the phenolic board, replace those two resistors, and paint it with Corona Dope:
.

It was a PITA - I hope you don't have to deal with this but if you do, there are lots of folks here who can give you pointers.

Carl


Here is what mine looks like after I got the arcing stopped:

Tubenut, thanks for the additional information about the corrosive nature of some silicones. Pernmatex sensor safe RTV seems to be the best bet. I still think the epoxy coat would protect against any acidic action of the RTV. I'm thinking if this flyback survived 62 years with the wax there shouldn't be a problem.

Have any of you who have restored TV's seen waxed flybacks actually be in good condition after this long?

[EDIT] Carl, did you have to replace the phenolic around the new socket? What am I seeing in this picture?

All of my 1940s and 1950s TVs have their original flybacks, except one from 1958.

I would clean off the sooty grime in that area using isopropyl alcohol.

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

Did not replace the phenolic board. The board looks new because I cleaned it really good. There were carbon traces in the phenolic causing arcing from a pin on the Socket, across the phenolic, to the metal chassis. To alleviate it, I had to cut out the carbon traces and replace the tube socket.

Also, did not know that any sharp points would cause arcing. So when I rebuilt the circuit using a new socket (Ceramic instead of Bakelite) and cut out the carbon traces in the phenolic, I got arcing underneath the chassis around that round metal Corona Ring.

Learned a lot about arcing - sound, sight, and smell.

Carl

Sounds like your set had some issues. I almost think it's better to learn on sets that are challenging, provided it's sucessful at the end. The sad radios I've worked on taught me patience for sure. I just hope I'm not being too nit-picky with every detail here, It's the way I work in general. I also like lots of photos. Tomorrow I'll get some supplies and on my next days off I'll get back to the chassis.

On the R80 3.3 ohm, What is the wattage on that? It looks like a 1 watt. Is it ok to up it to 2 watts? R77, 470k looks like 1/2 watt. Ok to up that one too?

What a great porthole. Just saw this thread. Have been off here for a week or two. I'm just like Carl, my first tv restoration was a porthole and my favorite. Now i didn't have the arcing problems on mine like carl had on his.

Is R80 and R77 the resistors in the bottom of the 1B3?
If so, 1/2 watt. 1 watt should be OK too unless there is a space problem.
If you replace those resistors in the bottom of the 1B3, take your time
and make some nice smooth connections.
Trim off the wire ends so close that a smooth blob of solder covers then wire ends.
This is one area you *have* to be super neat or you will be dealing with arcing issues.

Carl

Hey Brooks, when you finished your Porthole, were you working on an Admiral TV?
I'm finishing up my GE 805.
Looking for another Porthole project for this winter.

Carl

Nice restoration. Did your Bakelite cabinet have any cracks?
I've seen a couple that were highly polished and they really look good.

Carl