Bill, the first AL-1200's were built in 1985, not the mid 1990's, as you
said. You can check with Tom Raush W8JI, if you want confirmation. Willy
In a message dated 7/1/2009 3:01:01 P.M. Eastern Daylight Time,
amps-request@contesting.com writes:
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Today's Topics:
1. wd7s tu7b input board FS (Lynn Osterbur)
2. Re: AL1200, RTTY contesting, temps, duty cycles (not 100%)
(Bill, W6WRT)
3. Re: Sweep tube amp by DL9AH, made by HB9AWI (Bill, W6WRT)
----------------------------------------------------------------------
Message: 1
Date: Wed, 1 Jul 2009 09:55:54 -0700 (PDT)
From: Lynn Osterbur <no9z@yahoo.com>
Subject: [Amps] wd7s tu7b input board FS
To: amps@contesting.com
Message-ID: <347164.15212.qm@web110314.mail.gq1.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
? Used WD7S TU7b input board. Solder runs need cleaned up
A few silver mica caps included and 1 ferrite.
$10 plus shipping
Lynn NO9Z
------------------------------
Message: 2
Date: Wed, 01 Jul 2009 10:30:45 -0700
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
Subject: Re: [Amps] AL1200, RTTY contesting, temps, duty cycles (not
100%)
To: Kevin Normoyle <knormoyle@surfnetusa.com>
Cc: AMPS@contesting.com
Message-ID: <qg5n455diaf7iiomeas1snk42hddl34dgp@4ax.com>
Content-Type: text/plain; charset=us-ascii
You have done a good job of evaluating the situation, Kevin. I can add a
few
comments:
I purchased one of the first AL-1200's in the mid-1990s and used it for
RTTY
contesting. I ran it at close to 1500 watts at all times. I could not get
quite
1500 out with the TX I had, a TS-850S/AT, but I got about 1400-1450.
After I had it about six moths, I heard a loud pop and the lights went
out. Long
story short: The tube had failed. Ameritron replaced it under warranty and
the
replacement worked fine the rest of the time I had the amp. On all the
amps I
have ever owned (about a dozen) this is the only tube that ever failed.
But here's the Achilles heel of the AL-1200. The low band tank coils used
undersized wire and overheated. One time on 80 meters during a RTTY
contest the
solder holding the tap to the main coil melted, causing a nasty arc. I
resoldered it and there was no permanent damage. Think about how hot a
coil has
to get to melt solder!
The more serious failure occurred while CQing on 160 meter RTTY, not
during a
contest. There is no tap to let go so the whole coil overheated and melted
the
polystyrene rods holding the coil together, again with a massive arc and
lights
out. When I removed the cover it looked like a bunch of silver spaghetti
inside
:-) By then the amp was out of warranty so I had to purchase a new coil
from
Ameritron at a cost of about $26.00 as I recall. I replaced the coil and
there
was no further damage so the amp was back to normal.
At that time the designer of the AL-1200, W8JI, was a member of this
reflector
so I asked him about it. His reply - I'll never forget it - was "Well, who
works
160 meter RTTY?". Obviously he was talking to one.
I realized the amp was not going to do what I wanted (RTTY contesting) so
I sold
it to a CW/SSB guy and as far as I know he was happy with it.
If you look at QST ads from that period, they do not mention any
limitations on
duty cycle for the AL-1200. Now they do. I suspect my experience may have
helped
cause that change.
Later on I got to thinking I could have cut a hole in the side and mounted
a fan
to blow directly on the tank coils. Maybe I should have.
After selling the AL-1200 I had a series of commercial amps, an Alpha 91b
and
89, and a Command HF-2500. The Alphas both did fine on RTTY contesting,
the
HF-2500 fell short a couple of times (smoked toroid). I then got into
homebrewing and after a couple of false starts I now have an 8877 amp with
heavy
solid copper coils and an oversized blower and it will run
brick-on-the-key all
day, forever.
Finally, I am a happy camper.
So that's my story, hope this helps.
73, Bill W6WRT
------------------------------
Message: 3
Date: Wed, 01 Jul 2009 10:35:46 -0700
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
Subject: Re: [Amps] Sweep tube amp by DL9AH, made by HB9AWI
To: Angel Vilaseca <avilaseca@bluewin.ch>
Cc: AMPS <amps@contesting.com>
Message-ID: <bc7n45le104l7kb5ds8536lel11hho1pur@4ax.com>
Content-Type: text/plain; charset=us-ascii
ORIGINAL MESSAGE:
On Wed, 01 Jul 2009 13:47:44 +0200, Angel Vilaseca <avilaseca@bluewin.ch>
wrote:
>
>Yes, to obtain tha beautiful cherry red glow of the plates :-) a better
>option would be to increase the plate voltage. With only 600 V from
>plate to cathode, the cathode current gets too high and the poor little
>cathode is soon exhausted :-).
REPLY:
Sweep tubes are not intended to run with any color on the plates. If you
need
more output, bet a bigger tube.
I did TV repair for nearly 20 years back in the tube era. A glowing plate
is a
sure sign of incipient failure, trust me on that.
73, Bill W6WRT
------------------------------
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End of Amps Digest, Vol 79, Issue 3
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