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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? |
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Bob |
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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 |
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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.
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John |
Audiokarma |
#6
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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. |
#7
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$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 |
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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
__________________
John |
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Thanks for the info - I see exactly where to do that on the schematic
I dug up a couple serviceable 71As so maybe I'll have this radio running pretty soon. |
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