The repair of the electronics in the radiola superheterodynes of this period requires extra patience due to a somewhat strange manufacturing technique, not generally seen in vintage radio sets. The first radiola superheterodynes from 1924 to about 1927 (when RCA launched its first "AC" operated sets) were manufactured using a "catacomb"(as RCA termed it) circuit. That is, the circuitry was housed in a sealed container filled with beeswax! If a circuit failure occurred, I suppose the "catacomb' was exchanged at the factory for a new, sealed unit. This obviously makes the repair somewhat of a challenge. As repair outside the factory was not generally contemplated, there was only limited information published by RCA and later Ryders.
The Ryders Perpetual Troubleshooter's Manual for the RADIOLA AR-812 have been useful in providing an excellent means for ascertaining faults within the catacomb. I was immediately able to identify that the two inter-stage audio transformers were open and that the second I.F. transformer had an open winding. This meant that if a repair was to be undertaken, the beeswax would have to be removed.
Removal of the "catacomb" is straightforward; make careful notes of all connections whilst disassembling the receiver. I have found in the two cases I have had to access the "catacomb", the steel shell can be gently prised away from the beeswax. Simply unscrew the shell and carefully (if you plan to reuse them!) remove the leaden rivets with "RCA" printed upon them. Then slowly slide the shell off. I found that with the gentle aid of a fat bladed screwdriver, the shell may be levered at each side alternately, fractionally bit-by-bit.
When removed, the beeswax must be melted. I have attempted the melting by the oven and by a high temperature hot air gun. The hot air gun was preferable by virtue that it did not melt the insulation on the wiring; only the shellac coating on the insulating "spaghetti tubing" will have to be replaced.