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Re: [Amps] Alpha 70V conversion

To: <>
Subject: Re: [Amps] Alpha 70V conversion
From: "Paul Christensen" <>
Date: Sat, 9 Sep 2017 12:14:43 -0400
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">Would this amp lend itself to a 8877 tube conversion?  Mike"

Yes, but with quite a bit of work.  Also consider a 3CX1000A7 since it uses
the same Eimac socket.  

In either case, the condenser (radiator block) is removed and leaves a very
large rectangular hole that must be covered with an aluminum plate or sheet
metal. The rest of the liquid cooling system is dismantled and replaced with
air cooling.  The water sensor circuit is also bypassed/removed.  

The filament voltage requirement is fine since the 3CV1500A7, 3CX1000A7 and
8877 all use 5.0V.  Actually, the existing filament supply is very robust
when using an 8877 since the supply normally delivers 3x the 8877's filament
current to a directly-heated 3CV1500A7 cathode.  You also get the addition
of a filament choke that isn't used in Alpha's other 8877 and 3CX800A7 amps.

If using the 8877, you'll need to add a 3-minute filament timer.  Building
the circuit is easy enough but one can also find a surplus time-delay relay.

Like I said, it's a project - and requires more in the way of mechanical,
rather than electrical skill to effectuate the change.

Paul, W9AC

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