Tom,
Make sure you load the amp heavy...even if it reduces power slightly...real
slightly. I have had an AL80A which is the SB-1000 and it is a good amp...very
good. Just load it heavy
Lee - K0WA
The New Kansas QSO Party - August 29, Sat 9am-9pm and August 30 Sun 9am-3pm CDT
In our day and age it seems that Common Sense is in short supply. If you don't
have any Common Sense - get some Common Sense and use it. If you can't find
any Common Sense, ask for help from somebody who has some Common Sense. Is
Common Sense divine?
--- On Tue, 3/10/09, Tom Mandera <tsm1@tmcom.com> wrote:
From: Tom Mandera <tsm1@tmcom.com>
Subject: [Amps] SB-1000 - 100ma minimum plate current.
To: amps@contesting.com
Date: Tuesday, March 10, 2009, 12:46 AM
I'm new to QRO, but bought an SB-1000 (aka AL-80, sporting a single
3-500z) last week that belonged to a well regarded SK.
Finally wired things up tonight, bringing 240V to the amp.
I have the original Heathkit manual and I'm trying to follow through the
correct tune-up procedure, but I'm having difficulties.
I have 3400V with power on.
I dial back the exciter (TT Paragon II) as far as it'll go (less than
10w indicated, roughly 5w), set the band switches to match (80M in this
case), and find the initial settings from the manual.
I have no current in Standby mode.
I switch to OPR and key the exciter. I'm supposed to see 50-80ma of
plate, but I see 100ma immediately.
I then can't apply more drive and reach 50ma of grid without exceeding
200ma of plate. I reach 40ma of Grid and 200ma of Plate. I then adjust
for peak.
I'm then instructed to switch to the Power reading and adjust for peak
power again.
I heard the (tube?) sizzle (sounds like a good weld, not a good thing in
a radio) while attempting to increase the exciter drive to hit 125ma of
grid, and never reached it.
The manual notes more than 80ma of "idle current" is a Zener diode
failure (D2) which appears to be in the power supply, but I'm not clear
on what "idle" means - it doesn't indicate current in Standby,
but with
minimal drive from the radio, it doesn't go below 100ma. Is this a
failed diode?
I don't have any ALC hooked up, just the antenna (less than ~1.6:1 swr
at the test frequency) and the relay control from the radio.
Do I need to dig inside and have a look at the diode, or is there
something else I should examine first, or adjust in my operation, or
should the tube really sizzle (doubtful!)
Thanks,
-Tom
KE7VUX
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