[Amps] Amps Digest, Vol 79, Issue 3

K3vw at aol.com K3vw at aol.com
Wed Jul 1 12:12:15 PDT 2009

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 at 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 at yahoo.com>
Subject: [Amps] wd7s tu7b input board FS
To:  amps at contesting.com
Message-ID:  <347164.15212.qm at 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 at yahoo.com>
Subject: Re: [Amps] AL1200, RTTY contesting,  temps, duty cycles (not
To: Kevin Normoyle  <knormoyle at surfnetusa.com>
Cc: AMPS at contesting.com
Message-ID:  <qg5n455diaf7iiomeas1snk42hddl34dgp at 4ax.com>
Content-Type:  text/plain; charset=us-ascii

You have done a good job of evaluating the  situation, Kevin. I can add a 

I purchased one of the  first AL-1200's in the mid-1990s and used it for 
contesting. I ran it  at close to 1500 watts at all times. I could not get 
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 
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 
polystyrene rods holding the coil together, again with a massive  arc and 
out. When I removed the cover it looked like a bunch of  silver spaghetti 
:-) By then the amp was out of warranty so I had to  purchase a new coil 
Ameritron at a cost of about $26.00 as I  recall.  I replaced the coil and 
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 
so I asked him about it. His reply - I'll  never forget it - was "Well, who 
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 
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 
89,  and a Command HF-2500. The Alphas both did fine on RTTY contesting,  
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 
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 at yahoo.com>
Subject: Re: [Amps] Sweep tube amp by DL9AH,  made by HB9AWI
To: Angel Vilaseca <avilaseca at bluewin.ch>
Cc: AMPS  <amps at contesting.com>
Message-ID:  <bc7n45le104l7kb5ds8536lel11hho1pur at 4ax.com>
Content-Type:  text/plain; charset=us-ascii


On Wed, 01 Jul  2009 13:47:44 +0200, Angel Vilaseca <avilaseca at bluewin.ch>  

>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  :-).


Sweep tubes are not intended to run with any color  on the plates. If you 
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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