Substitute for 183/483 tubes
 

Any ideas for subbing 183/483 audio output tubes? Between my two Sparton radios I need 4, but only have one :( They're hard to find and expensive.

I read elsewhere that a 71A is a possible substitute. Can anyone confirm that? Would I need to alter the bias or wiring?

According to my 1951 Rider Tube Subsitution Guide Book the 71A is an "Excellent" sub for the 183/483 with no changes necessary to the circuit. They also indicate that a 182B/482B will sub.
Bob

My 1945 "Sylvania Aids to War-Time Servicing" lists the 71A as a substitute for the 182B but not the 183.

For the 183 they list 182B/482B and 12A. They suggest changing the bias or plate volts for the 12A. The 12A has a different filament current which would affect a series application.

They also list the 45, 46 and 2A3, but these require more intensive modifications.

It's curious that they list the 71A as a substitute for the 182B but not for the 183 even though the 182B is listed as a substitue for the 183. Maybe they intend for you to refer to it. If so, they also suggest a bias or plate voltage change for the 71A for best performance.

John

Thanks for the info guys. 182s seem to be even rarer than 183s, but 71As are somewhat common. I only have one right now, but I think I can track down some more.

I think I've acquired more than I need. I'll try to see how many I have. But, you're not getting the blue Arcturus ones! :D

John

Thanks! I'll take what I can get :D My only 71A is an ST type.
I just did a little comparison of the 183 and 71A.
Same 5 filament, but the 71 draws only 0.25A vs 1.25A for the 183.
Also the 71A is about 0.8W vs 1.8W. Other than that they looks pretty close.

:sigh: :eek: :yikes: $362 for five 183 globe tubes!

I might as well sell the one I just picked up for $2 rather than try to get some more.

FIVE GLOBE SHAPE RCA SPARTON 183

I made a note about subbing 71A's for 183's in the Sparton Jr. In another forum someone said you'll need to change the bias resistor that goes from the center tap of the 5 volt filament winding from 1250 to 1800 ohms 2 or 5 watt. If you don't change this resistor, the 71As will exceed the design max plate dissipation. Credit for this goes to Chuck D. KB9UMF over at ARF:

http://antiqueradios.com/forums/view...e61baa8b0f2a2f

Thanks for the info - I see exactly where to do that on the schematic :yes:
I dug up a couple serviceable 71As so maybe I'll have this radio running pretty soon.