[Phlogiston]

   

   

I think some people call this a "catacomb". I call it the formally potted IF, detector and audio sections of a Radiola 25. Just thought you might like to see what is inside without having to remove the wax.

I replated the metal box and top.

Will post finished pictures on my blog.

[morzh]

Oh geez.....I don't wish that upon muyself. Hate coils.

[Phlogiston]

Oh geez.....I don't wish that upon muyself. Hate coils.

This is a super. Supposed to have I stage of RF. So the transformers from the left are:
Primary (thin)
Secondaries that are CT (thin side by side)
Spool that is pri and secondary
IF primary and secondary
IF primary and secondary

End of first core which is common for all above.

First audio
Second audio

[KCMike]

  That must have been quite a challenge to un-pot the wax without damaging any of the coils. Good job.

[sam]

 Hey Russ
I have 4. Rca26 's. 
I unpotted 1 some small wires broke 
Lot of rosin though  never got back to it 

Sam

[morzh]

Question: any reason to unpot short of some opens that developed over time?

[Jayce]

This is very interesting to see since I got a Radiola Superheterodyne in the collection now. I also wonder if mine actually decides to work, if there would be any reason to unpot the thing. Also, if I ever have to (I'm fine with it just being a show piece), would I have to repot the thing or just leave that crap out?

[morzh]

Potting keeps the elements out so the wires don't oxidize as readily. Plus some imobilizing which helps.

[Phlogiston]

There are about half a dozen mica caps and 1 carbon resistor inside of that assembly, but the most common failures are the audio interstage transformers. Now, having said that, I just emptied that one to look at it - yeah, I know.

I did end up replacing all of the cloth covered wire. It was getting crispy. And I replated the can and the top metal around the tube sockets. It looks much better and I could not have done it with the can still potted.

I will tell you that the catacomb can be drained without making a mess of the tube sockets. Trick is that you have to remove the can top, which is formed and soldered in place. So this is a bit of a challenge by its self especially if you want to but it back on. Turning the housing so that the wax drains away from the tube socket board. I can't imagine cleaning the hard wax out of the sockets and wire connections. You can see the top of the can in the second pic of the first post. It has been reassembled at that point.


It is all back together now. I'll probably fire it up in the morning.

Don't have any resized pictures now and I don't want to mess with that. But I did post some with the cabinet and with the interesting store logo on my blog.

[Arran]

Potting keeps the elements out so the wires don't oxidize as readily. Plus some immobilizing which helps.

Mike;
  The reason that I was told as to why RCA had these potted was supposedly to discourage rivals from reverse engineering their superheterodyne models. I don't know if this entirely makes sense as RCA, as a patent pool, had a virtual monopoly on the superheterodyne circuit which only allowed G.E and Westinghouse to manufacture them, and under which they issued threats of litigation with great zeal. Whether it was potted or not, patent protected or not, it still did not prevent other companies from infringing on their patents, particularly the makers of kit radios. In any event I have a Canadian Westinghouse model 89, which I think is similar to an RCA Radiola 62 or 63, and none of the RF or IF coils are potted, only the condensers, chokes, and the power transformer, so they obviously thought that it was unnecessary by 1927-28.
Regards
Arran

[Mondial]

RCA really did not want people going into the catacomb box. Beside the potting, they used lead seals, embossed with the RCA logo inserted into some of the rivet holes. It would then be obvious if anyone opened or tampered with the sealed enclosure.

I opened up one of these boxes many years ago and was amazed at the lengths RCA went to to conceal what was inside. Don't know what they were thinking, as anyone determined to do so could get inside and see what was there.

[Jayce]

Wow, what an RCA created headache to just get inside that can! From what the seller told me, the man he bought my radio off of was rather up in his years and recalled it was still working when it was finally put out in the barn. Maybe there is a chance it will still fire up if I ever get a power supply rigged up for it. I have the matching horn, but I don't think I have the adapter needed to plug it into the socket on the front of the unit. I used to have one of those years ago I took off an early set of headphones, but I can't find it.

[morzh]

There is no can box that would stand to a good can opener

[Phlogiston]

I put the two led rivets back. I did not notice an RCA stamp, but they are very soft.

It doesn't seem that there were many of these table top units, maybe more as a phono/console combination. That application used a loudspeaker with a separate audio output transformer.

[Phlogiston]

Decided to build a new ABC supply. Should be done in a few hrs. Then I'll test both radio and the supply. I needed a better 45V source. All of my other supplies were set up for a single detector (1 toob) on the 22 - 45V tap.