Re: [Amps] 4pr-1000b,Y448 tubes

[Bill Fuqua <wlfuqu00@uky.edu>]

I have talked with R. Brandon at EIMAC (CPI) about this. It seems that they 
are 4-1000A and the 4PR1000 tubes are the same.
The 4PR1000b tubes are taken off the production line of the 4-1000A tubes 
and then they are tested with 30KV on the anode. The voltage is raised 
slowly to condition the tube until it reaches the max. They perhaps go a 
little above the 30KV but that is only speculation on my part. Most of the 
4-1000A tubes that they meet the requirement right off the bat because they 
are rated for plate modulate AM applications with 5500 volts plate voltage 
which translates to 11,000 peak voltage (more than 1/3 of the PR 
rating).  He just sent me the newest version of the Care and Feeding of 
Power Grid Tubes which has much more material in it than the old version 
(now 173 pages).

Conditioning is a routine where you slowly increase the voltage until there 
is a flash over or there is a sudden increase in current. The flash over is 
usually due to small pointed or irregular surface feature that the flash 
over evaporates. And then you can try again.

By the way don't use any Triton 4-1000 or 4PR1000 tubes. They have not been 
able to make them reliably. Every new Triton I have tested before they go 
to into service in a linear accelerator  has failed due to gas or low 
emission or both. The best tubes are the Amperex made by Covimag in France. 
And they have graphite anodes as well. This instrument has been getting 
over 2  years of continuous service from the Amperex ones. They have even 
switched from the 4PR1000 to 4-1000 tubes. Their plate voltages in the 
power oscillator runs up to 8 or 9 Kv.

One caution about used 4PR1000 tubes. If they are used in pulse 
applications they often can look perfectly good (no brown color on the 
glass envelope) but be low on emission. In some applications they run them 
until they are really flat. I guess that may be because they are often run 
in pairs and the stronger tube can keep things going.

73
Bill wa4lav



At 02:22 PM 12/10/2003 -0700, you wrote:
> I have searched google for details on the diferances between the
> 4pr-1000b (pulse tube) and the basic 4-1000a and have found limited
> information.
>
> My HB 4-1000 amp, GG with 6Kv anode voltage performs well, but just
> today realised the tube is an Eimac 4pr-1000b....I can just read the
> faint red print.
>
> What "real" difference is realised by using the pulse rated tube and the
> "standard" 4-1000a ??
>
> Also, any experience out there regarding using the National Y448 tube? I
> have the oportunity to purchase one of those...will they function as
> plug-and-play replacements to a 4-1000? Reliable?
>
> Steve ve6wz.
>
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