A month or so ago, my cousin visited me with an unusual gift. He discovered an old machine being scrapped and rescued for me (knowing my hobby) two Eimac 4PR-1000 tubes, with the chassis mount (blower fan included), two sockets, clamps and chimneys. You may figure my surprise when I saw him at my house's door with such bottles in his hands. The tubes where rescued from a medical equipment, so I don't know the performance, although they look visually good indeed. I read somewhere these are improved versions of the 4-1000 types, is this ok?.
There is a chart for AB2 grounded cathode work in the ARRL handbook ('97) which states 3000V plate voltage, and an idle current of 300mA. This while idle means you are nearly maximum rated plate dissipation, is ok?.


Best regards
Guillermo - LU8EYW.

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Guillermo: To be linear, a 4-1000 needs to be run either in Class AB1 grounded-cathode, grid-driven or Class AB2 g-g, cathode-driven. For SSB, anode supply potentials of 6kV to 7kV are common. For AB1: a screen supply of 1000V is needed to make maximum output, and Bruene bridge-neutralization is not a bad idea above 15m.
cheerz

On Sep 16, 2006, at 5:04 AM, GGLL wrote:

A month or so ago, my cousin visited me with an unusual gift. He discovered
an old machine being scrapped and rescued for me (knowing my hobby) two Eimac
4PR-1000 tubes, with the chassis mount (blower fan included), two sockets,
clamps and chimneys. You may figure my surprise when I saw him at my house's
door with such bottles in his hands. The tubes where rescued from a medical
equipment, so I don't know the performance, although they look visually good
indeed. I read somewhere these are improved versions of the 4-1000 types, is
this ok?.
There is a chart for AB2 grounded cathode work in the ARRL handbook ('97)
which states 3000V plate voltage, and an idle current of 300mA. This while
idle means you are nearly maximum rated plate dissipation, is ok?.


Best regards
Guillermo - LU8EYW.



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r@...

--- In ham_amplifiers@..., "David C. Hallam"
<dhallam@...> wrote:

Guillermo,

The PR version of the 4-1000A stands for pulse rated and simply

means the

internal structure will handle very high current on a intermittent

basis.

Others may give you a different take on the idle current, but not

having a

copy of that handbook I would think that is for 2 tubes. ZSAC (

zero signal

anode current) for AB1/AB2 is generally adjusted to give about 1/2

of the

rated dissipation of the tube(s).

### The PR version will handle sky high plate voltages...
like 10-30 KV.

### In GG... with around 7 v of zener bias.... and 4800V... I
was seeing around 70 Ma ZSAC. [single tube]

### A small SPST CENTER OFF toggle switch and a string of
diodes will provide 3 x bias positions..... and a rotary
switch is the ultimate set up. I also found that the vdrop
across the string of either 1N5408's or 6A1O's [ 1 kv - 6 A..
400 A surge] diodes increases from aprx .7 V to almost .8 V
when current thru em increases from 200 ma to 2 A.

### I installed 7 x 1000 uf lytics in parallel [7000 uf]
across the entire mess of diodes...... resulted in superb bias
regulation. Just beware... the wire leads from the diodes IS
the heatsink for the diodes. The 6 A diodes run luke warm
with 2 A CCS thru em.

Later... Jim VE7RF

David
KC2JD