[Amps] New Ameritron AL-80B Tune Up

[Jim Thomson]

Date: Mon, 15 Aug 2016 19:01:38 -0400
From: "Thomas F. Giella W4HM" <thomasfgiella at gmail.com>
To: <amps at contesting.com>
Subject: [Amps] New Ameritron AL-80B Tune Up

I purchased a new Ameritron AL-80B and the manual is not totally clear to me 
as far as tuning it up without damaging the 3-500Z, especially how to set 
the ALC to prevent overdriving. Could someone that owns one please give me a 
basic guideline on how to safely tune the amp up?

73 & GUD DX,
Thomas F. Giella W4HM
Lakeland, FL, USA

##  what  xcvr are you using ?    Does it have adjustable power output ?   If so, Id
suggest NOT using the ALC cable from xcvr to the AL-80B.   IF the xcvr has a built
in CW keyer, lock up the dots, either via the paddles or a plug into cw jack, such that
only dots are emitted.  Crank keyer speed up to max, like 60 wpm.   Use a footswitch
to activate the PTT line.  This leaves both hands free. Dont use VOX.  Start off with xcvr
on low power output, like 10-20 watts.  

##  with amp on correct band, and tune and load set per the manual  for  aprx settings
for the band in question, and with either a dummy load, or correct ant, hit the 
footswitch, and tweak tune 1st, then the load,  for max power output. ( PO). 
You should see a rise on the built in pep wattmeter.   RLS  footswitch, then Increase PO 
of the xcvr a bit more,and hit the footswitch, then again re-tweak the tune + load for max
PO on the pep  wattmeter.   Repeat the process, till  you achieve rated PO  of the amp,
which I believe is aprx  1 kw.   You may well have to alternate between the tune and load
caps a few times for each xcvr PO setting, to fine tweak the amp  for max PO on the amp. 

##  By using 60 wpm dots, you are pulse tuning the amp, so the duty cycle will be real low,
and a lot easier on the tube and power supply + ant + balun etc, etc.  Your plate and grid
current meter readings will  be aprx  1/2  of what they are if using a key down dead cxr.

##  The AL-80B uses an obscure  2 x stage alc adjustment. It was designed to send a  neg low dc 
volatge back to the xcvr,  so u don’t over drive the amp, which is great if the xcvr does NOT have adj
PO.  There is also a 2nd adj in there to increase the average po of a ssb signal.  Sorta like a form of RF
speech processing.   Dont run the ALC cable..and use the processor inside the XCVR.

##  Once the xcvr is switched back to ssb mode, the PO of the xcvr may or may not be exactly the same.
Retweak the PO of the xcvr if required, so the pep out on the amplifier is the same as when you pulse
tuned it. 

Jim   VE7RF