Considering a Radiola 25
I was debating whether or not I should buy an RCA Radiola 25. For one, it needs '99 tubes which aren't cheap. Plus it has most of the RF, IF and AF transformers potted in a metal catacomb. Not to mention that the IF frequency is 45 kc, so a bad IF transformer would be hard to replace.
Judging from the experience I had with my Radiola X, which had both AF transformers open, a Radiola 25's are probably shot as well. Add to that the fact that the caps are inside the catacomb, it's a sure bet that thing would need opening up.
Anyone have any success with one of these sets? Thanks; don't want to shell out a pile of money for something I can't fix...
The catacombs are not as bad as one might think. A 250 degree oven and your in business. The resin is not nearly as bad a the AK tar. In-fact when melting it resembles a pine tree.
I have one that had a bad audio. One replaced it works great.
I am quite pleased with the performance of mine. If you keep an eye out on E-Pay you can fine 99 tubes relatively cheap. I think the last batch of 6 I purchased I paid $45 for. They were untested but with good filaments.
I recommend a 120 for output tube as well.
The RF and IF coils are never bad; any problems would be with the flying leads which get broken when the wax shrinks. Once you melt out the wax (which doesn't have to be replaced) everything is accessable.
Well, I went ahead and bought the Radiola 25 today. I have a Trav-Ler type T portable set with five 99's (most are weak) in it, and I have a few 20's I could use for the AF output. So I think if I use my best '99 for the oscillator, I should be set for tubes. And I've managed to repair a few RF coils with bad lead ends, so off I will go...
Oh, BTW, will I need to unsolder the catacomb and remove any panel(s) before I commence meltdown of the resin? I'm picturing resting the whole assembly on a rack in the oven, with a pan on the lower shelf to collect the drippings. Perhaps once I actually look at the assembly, it will become clearer...
Assuming it works the same as a Radiola 26, cut the seals below (you can glue the visible half back on later, for appearance) and set the can in the oven. When the wax is all melted, simply lift out the works. You can pour out the wax for use somewhere else.
Don't rush the job, give it several hours at least to melt. The transformers take a while to reach melting temperature.
Over the years I owned a few catacomb sets. I never found an early one with UV199's with good audios. I still have my AR812 Radiola Superhet and a Radiola 26. I sold my floor model Super VIII. All were bad.
I only had one UX style that was bad. I have had a Victor Florenza with a Radiola 25 panel, a table top Radiola 25 and a Brunswick AC operated Radiola 25 panel and all were good. As far as 8 tube UX style catacombs, I have had a few of them including 3 Radiola 28's, one being found in the trash with a good set of 199's and a good catacomb but a weather beaten cabinet, and a Victor 9-55 Automatic Electrola with A.C. operated Radiola 28. The only one that was bad was one of the floor model 28's.
Meter out your catacomb before you start melting it down. It just might be good.
I have a radiola 25 and you can use 30 tubes with a 31 for the output.
If you have to repair the catacomb, you can also melt the resin with boiling water in a large canning pot. . I did this outside on the BBQ as my wife and daugher objected when I started on the kitchen stove.
I have also done a Radiola superhet the same way however it only needed broken wires reconnected.
I was thinking about whether or not the 30 would work on this set, cool thing if it does, 'cause I have some lying around.
So, assuming I'll end up melting wax, I'm still curious about how the cat comes apart. From the picture of the set I see a plate on top above the tube socket board. Do the tube sockets have to be desoldered, or do they come out with the rest of the guts? Also, there is a long terminal strip on the rear. I assume that must be desoldered. Then I heat it up for 3 hours, and everything pulls out straight up.
I guess it would be better for me to wait until the catacomb is actually on my bench, then it might appear more obvious how it comes apart. Maybe I'll luck out and the "cat" will be good. But still, there are caps and a grid leak resistor in there too. They could be due for replacement. Not that I'd know what values to use...
Don't think you can make a #30 fit? Most of there early RCA superhets used UV199's.
Looking at the photos of the set on Ebay, they look like they would take the UX base. There are the standard two big pin holes, two small pin holes, and no signs of the bayonet-type socket. My 99's and 20 all have the UX base, so I'm hoping it's really UX's on this set.
The only tube I've ever gotten with the UV base is a UV201A I found in a Music Master set. And from what I understand, you could put a UX tube in a UV socket. But a UV tube won't stay in a UX socket. Of course, the '99's have a smaller diameter base, so I don't know how their bases compare.
I'm just wondering... Maybe when the UV base went out of vogue, radio parts makers made aftermarket kits to convert sets to use the UX. They made kits to convert battery sets to AC, so why not? But they also had mass cremations of battery sets when AC sets came to be, so I could be wrong...
It is possible to evaluate a catacomb from the outside before opening it. I have found the best way is to put voltage on it with no tubes in place and measure at each tube socket terminal to see if voltage is present. This will detect broken wires and open audios.
If you have to open it, disconnect the wires (which RCA calls "whiskers") from the terminals. Make a sketch of where they go. Then remove the top plate from the cat, saving the lead seal as noted. Heat it until the resin is liquid and remove the chassis. It comes out in one piece.
I suspend the chassis on a pair of wood blocks in a large tray and continue heating so the resin will drain off into the tray. Empty out the bottom half while liquid. You will not reuse the resin.
This resin has a pleasant aromatic smell, so the wife shouldn't mind your using her oven. 270-300° is about right for melting the resin.
Broken coil wires are common. The resin shrank and cracked over time and if one of the fine coil wires happened to run across a crack, it would be pulled apart.
By voltage testing the cat, you will know where the problem is before opening it. You may have a good cat. I have seen several in perfect condition.
Don't quote me on this, but I understand it this way.
The UV sockets were designed for the short pin tubes and had a bayonet pin on the side to lock them into the socket. The later UX series of tubes still maintained the diameter of the base and the bayonet pin, and the only difference is in the length of the tube pins. The sockets were interchangable, as the location of the bayonet pin on the UV tubes is located higher up on the side of the tube by a distance equal to the difference in pin length between the UV and UX tubes.
Clear as good old Mississippi mud, aint it?
(Connoisseur of the cold 807) CW forever!
Not a problem if you have UX sockets. One thing about 99's. UX & UV tubes have different basing. UX has filaments on two large pins. UV filament pins are diagonal.
The 30 tubes will fit and I have 6 of them in my radiola 25. However ,they will not fit a radiola 28.
Curt, what you say is true of the 01A tubes, but the UV/UX199 tubes have unique bases and are not interchangeable.
I realize the 99 has a much smaller base, but I didn't mention it in the original posting and forgot to edit it later. Heck, I have two dud UV199's on display on my computer at home.
(Connoisseur of the cold 807) CW forever!
Can someone point me to a pic or drawing of a catacomb?
Here's a very good photo of an AR-812 6-tube catacomb found with a Google search:
There is an good schematic of the radiola 25 in Hugh Gernsback "Official Radio Service Manual for 1930". It also contains info about the catacomb. This is what I used when repairing my set and it was very helpful. Plse advise if you would like a copy and I will forward.