[Brad Winder]

Ok, here we go...Waaaaaay back, to a radio that was an archaic antique, even when most of the radios we currently discuss on the forum, were new. 
My friend just bought a Westinghouse RA-DA, designed in 1920, and stubbornly sold by RCA until 1923, even long after it was obsolete. I read that they made a ton, and were stuck with thousands in overstock.

Anyway, his is missing it's tubes. He's been told it needs three 200 tubes...I cannot seem to find any specs or cross reference for this tube. Has he been informed correctly? Would a 201A work in it as well?

[Arran]

Brad;
  The RCA branded RA-DA, alternatively known as an RC unit, was branded for sale as such, however in the Canadian market Canadian Westinghouse also marketed and sold these under their own name, much like the Aeriola Seniors and the Radiolas III and IIIA. The latter were also made by Canadian G.E whom modified the design to accept UV 199 tubes as opposed to WD-11s. With regard to the RA-DA sets I think that they will work with 201As, at least in the amplifier section, the 200 and 200As were intended for use as detector tubes, I think Russ would know as he recently had one for sale.
Regards
Arran

[Chas]

RA-DA initially used 2 x uv-201 and one uv-200 detector, one amp filament tubes.

There was a modification to the rheostats to use 2 x uv-201a and still use the uv-200. What the set requires depends on the resistance of the filament rheostats.

Later ux-201a's and ux-200a would work, 1/4 amp filaments. If the intent is to operate then the rheostats and the tubes chosen are important. For the one amp tubes a low impedance filament power source is required.

The '201a may be substituted for the gas detector 200a, moving the tuning circuit return from A+ to A- may be required if satisfactory sensitivity and regeneration control cannot be obtained.

The one amp filament tubes are tungsten, very bright when in operation very little if any getter deposits. The 1/4 amp tubes are thoriated tungsten, will operate at a medium orange color, thorium is diffused through the filament but the active layer is on the outside. The 1/4 tubes can be rejuvenated if the thorium layer is depleted.

There is far fewer one amp tubes to be found, therefore they are generally more costly...

YMMV

Chas

[Phlogiston]

It will work with 1/4 amp tubes, though you will loose much of the filament control - so this must be done with your power supply.

The one I sold would operate nicely with as little as 9V for B+.

[Brad Winder]

Update: my friend has the radio in hand, and started cleaning, etc. He sent me a couple pictures, and I noticed that it had adapters installed in the sockets, to allow 199 tubes to be used in it! And sure enough...he found a tube, laying inside the bottom of the cabinet.

[Phlogiston]

Are the adaptors for UX or UV tubes?

If you are already aware - sorry. If not - this is very important since the tubes are based differently (pin-out).

In any case the 201(A) would be a better option.

[Arran]

I would save the 199s for another radio, the 201As are a better option in my opinion, since the 1 amp 201s were what was originally used, they are closer in looks, and in filament characteristics to the 201s. I think that if you were not operating the set from a power supply then you could add resistance to raise the current draw, such as paralleling a resistor across each tube filament, this assumes that the RA-DA was not a later production type, nor was modified to accept 201As, it may have been modified to accept 199s for that matter, such as by installing a different rheostat. As Russ mentioned the pinout of a UV 199 is different from a UX 199, I think that the plate and grid pins were swapped to match those of a 201a on the UX.
Regards
Arran