----- Original Message -----
From: "Dennis W0JX" <w0jx@yahoo.com>
To: <Amps@contesting.com>
Sent: Wednesday, September 22, 2010 2:41 PM
Subject: [Amps] Options for the AL-1200
Re tube changes for the AL-1200:
1.) See N9ADG's website. About four years ago, several hams put the GS-35b
into their
AL-1200's. This seems to work ok except that the cooling is below minimums
and a
bigger (noisier) blower is required along with a different filament
transformer and bias
circuit;
2.) Another workable option is to put in an 8877. You will need a filament
transformer
change, socket, and chimney, and you will need the timer and grid current
trip curcuit to
protect the 8877. You might need to tweak the tuning/ and or components of
the tuned
input circuit;
** No change needed for the filament transformer except a resistor to
compensate for the lighter load. Adjust it for 4.8V for well extended life.
3.) IMHO, swapping to a pair of 3-500's is a great option although they need
more drive than
the 3CX1200A7. However, you will retain the "quick on" feature of the amp
and the tubes
are cheap! You will need a new filament transformer, sockets, chimneys, and
suppressors;
** And you risk the same problem as the stock AL-82, sudden IED events. That
amp runs on the ragged edge. I suspect that GG 4-400 or 4-500's would be
more stable.
Carl
KM1H
Luckily, all of the necessary parts for the above (except the GS-35b option)
are available from Ameritron at very reasonable prices.
73, Dennis W)JX/8
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