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[Amps] Tube swap

To: <amps@contesting.com>
Subject: [Amps] Tube swap
From: "Jim Thomson" <jim.thom@telus.net>
Date: Mon, 27 Jan 2014 19:45:25 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Date: Mon, 27 Jan 2014 21:56:48 -0500
From: "Karel" <kebenstr@bmts.com>
To: "Carl" <km1h@jeremy.mv.com>, <amps@contesting.com>
Subject: Re: [Amps] Tube swap

How do you check if they leaked?
Should there be a whitish discoloration inside the tube?
I will check mine later next month. Right now my amp stuff in under 4 feet 
of snow here in western Ontario.
Karel, VA3KO

##  You will know in 2 seconds flat..when you 1st apply  7.5 vac to the
cathode.  I had 3 of em go up..literally like a smoke bomb on the inside of the 
glass. 
They had lost part of their vacuum.  Turn on the fil..and all of a sudden, tons 
of white
smoke billowing round and round on the inside of the tube.  The fil went from 
the normal
white colour to super white..then poof, fil goes out. Event over.  The smoke 
eventually stops,
and deposits itself on the insides of the glass. 

##  I had picked up 7 more tubes  15 years ago....and tested em one at a time.  
 3 of em went up
in smoke asap. That is the 1st time I had ever seen a 4-1000  turn into a smoke 
bomb.  A good 
4-1000..with 4400 vdc under load of 600ma, will do 1900w pep out with 130 w of 
drive. The input
Z is 100 ohms..not the 65 ohms of a 3-1000Z......so ur tuned inputs will be out 
to lunch.   The SAME
tube..with 2500 vdc under load of 400ma..and the same 130 w of drive did 600 w 
pep out.  The
4-1000 needs more B+   on it to work correctly.   The gain of the 4-1000  goes 
way up with more B+. 
Another tube that will also work is the 4PR-1000A....which is the pulse rated 
version..rated for 15 kv.
It will drop right in..and function the same as a regular 4-1000. 

##  IF  you are buying used 4-1000s.... make sure you have a provisio that if 
the tube is no good, you
don’t pay for it.  In the old days..back in the 70s... the seller sent the 
tube..I plugged it in.  If I liked what 
I saw, I sent a cheque.   If not, I sent the tube back.   At least get the 
seller to apply 7.5 vac to the fils for
3 secs.. to make sure you don’t have a smoke bomb.   You don’t need a socket, 
chimney nor blower to do the
2-3 sec smoke bomb test.    A soft tube will do like 1100 watts out  with 4400 
vdc under load.   A good one
will do  1900-2000 w out. 

##  I suspect your  3-1000Z  amp only had  3000-3500 vdc on the tube.  So even 
if a good 4-1000 is used, don’t
expect a lot of power from it.   IF the input swr is high, power out will drop 
like a rock on a 4-1000.   

Jim   VE7RF


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