[Amps] Tube swap

[Karel]

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 at telus.net>
To: <amps at 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 at bmts.com>
> To: "Carl" <km1h at jeremy.mv.com>, <amps at 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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