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Re: [Amps] Tube swap

To: "Jim Thomson" <jim.thom@telus.net>, <amps@contesting.com>
Subject: Re: [Amps] Tube swap
From: "Karel" <kebenstr@bmts.com>
Date: Tue, 28 Jan 2014 09:50:40 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Thanks Jim,
very useful information. 2 of my tubes are still in the original box. They were unopened when I got them, so I did not bother testing them. When I got them, I just opened one to see if they are physically there.

By the way, as I was typing this e-mail, I just found both new in box tubes inside the closet of my room in the house. One is still unopened. The used ones are in the shed. The one I took out looks crystal clear. I will try to get some 7.5 VAC power supply and test at least the one out of the box. They were made by RCA. I took some pictures, is there a way to attach them to the post in this group?
Karel Ebenstreit, VA3KO

----- Original Message ----- From: "Jim Thomson" <jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Monday, January 27, 2014 10:45 PM
Subject: [Amps] Tube swap


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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