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Heathkit AA-15 output transistor replacement.

M.Yu

M.Yu

In the Vintage Vanguard
I am looking for a suitable replacement for the RCA 417-139,
AKA 40411 (I think) transistors for my Heathkit AA-15

One recommendation I was given turned out to be incorrect.
After looking at all the datasheets, I am confused about which to use as replacements.

The info I found says these are NPN 90V 30A 150W - not sure of the MHz

Does anyone know what might be the best choice to replace these?

Thanks!
 
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Most output transistors are not critical at all as long as they can handle voltage and safe operating area. The AA-15 is the same as the amplifier portion of the AR-15 receiver. Power supply is a single supply shown as 72 volts but could be higher with todays higher line voltage. You want transistors with Vceo of at least 100 volts.

A good modern replacement that has nearly double the SOA of earlier power transistors is the MJ21194 or MJ21196. They are nearly identical and both are readily available from Digi-Key or Mouser at reasonable prices. Some people have MJ15015 laying around and these will work ok also. MJ802 is also acceptable, but seems to be of limited availability new.

I have 2N3055 in the AR-15 but with the Vceo of only 60 volts, I can't run it up to maximum power.

The important thing is to replace BOTH transistors of a channel.

If your transistors are bad, the drivers might also be bad and the emitter resistors could have gone open. While you're at it, get a couple of small TO-5 heat sinks for the 40408 VAS. For driver replacements, I just bought some Fairchild KSC2690 (NPN) and KSA1220 (PNP) for a Fisher 600-T redesign/rebuild. These are TO-126 packages and should work to replace the 40409 and 40410 but you should also add small heat sinks.
 
Hi,
I recently had my AA15 fully repaired but have one big problem. The stereo does not work. It only works to mono and when I switch to stereo the sound is very low (I can barely hear the song playing).
Any suggestions on how to fix this will be highly appreciated
 
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