[Amps] Options for the AL-1200

[Carl]

----- Original Message ----- 
From: "Dennis W0JX" <w0jx at yahoo.com>
To: <Amps at 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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