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Re: [TenTec] In praise of older technology

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] In praise of older technology
From: Kimberly Elmore <cw_de_n5op@sbcglobal.net>
Reply-to: Kimberly Elmore <cw_de_n5op@sbcglobal.net>, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Wed, 5 Mar 2014 10:30:33 -0800 (PST)
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
One other thing: The AL-*)A meter would only read B+ up to 3500 V. You''ll have 
change the meter shunt resistor. I changed mine such that the meter now read 
B+/2. Thus, 4 kV yields a meter reading of 2 kV so the scale is x2. An 
AL-82/AL-1200/AL-1500 meter (they're all the same) could also be used along 
with the meter shunt used in any of the amps for which the meter is designed. 

Kim N5OP


________________________________
 From: Kimberly Elmore <cw_de_n5op@sbcglobal.net>
To: Discussion of Ten-Tec Equipment <tentec@contesting.com> 
Sent: Wednesday, March 5, 2014 12:19 PM
Subject: Re: [TenTec] In praise of older technology
 

Yes, that's the one. As far as I know, I'm the only guy to ever buy one!

The mod isn't trivial. You'll need to change the filter capacitor stack and 
build a FWB rectifier instead of using the original FW doubler. If you raise 
the B+ you change the plate impedance and so will have to change the output 
tank a by adding some inductance. You'll also have to change the bias on the 
tube. For the output tank, the lower the frequency, the more inductance you'll 
have to add. 160 m is the toughest to tame; I made a powdered iron toroid 
inductor roughly equivalent to the one that's already in there for 160 m and 
placed it under the stock large air-dux inductor. It has very high RF voltages 
on it and so will need some serious insulation between it and the bottom the 
case. I used about 1/4" rubber sheet. You'll then need to move the taps for all 
the bands up through through 20 m. I did this by experimentation so that I had 
the load and tuning controls where I wanted them (they no longer strictly match 
the guide on the front panel). You'll
also have to be very careful tuning it because the RF voltages are much higher, 
now. It must never be run lightly loaded as you are certain to flash over the 
band switch. Once I figured it out and put stick-on markers for tune and load 
pointers, it was easy

I upped the bias on the tube based on the Eimac spec sheet. Failure to do so 
will cause the tube to dissipate more than 500 W in an idle condition. I've 
forgotten what the new Zener value had to be, but it was a stock value and the 
idle bias is set to be (I think, it's been a while) about 60 mA. The primary 
requires 240 VAC -- you'll no longer be able to run it on 120 VAC.

Kim N5OP


________________________________
From: R. Eric Sluder-W9WLW <resluder@yahoo.com>
To: "cw_de_n5op@sbcglobal.net" <cw_de_n5op@sbcglobal.net>; 
"tentec@contesting.com" <tentec@contesting.com>; "tentec@contesting.com" 
<tentec@contesting.com> 
Sent: Wednesday, March 5, 2014 11:35 AM
Subject: Re: [TenTec] In praise of older technology


That explains the upgraded Peter Dahl transformer you can still buy for the 
AL-80a.  I've considered swapping my transformer out because it looks a little 
weary for its age and such.  I fear a short could be in its windings in the not 
to distant future.  My amp I believe came from a moist environment, and that is 
why I have the concern over a short.  The outer paper layers don't look their 
best.<br/><br/>Eric<br/>W9WLW<a 
href="https://overview.mail.yahoo.com?.src=iOS";><br/><br/>Sent from Yahoo Mail 
for iPad</a>
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