The AM Forum

Is the 8166 the 4-1000A and the 8189 the 4PR1000A/B directly interchangeable in R.F. Service? Certainly the sockets are the same , the  5 pin special. The 8189 was slightly redesigned for Pulse Service. Message from Jim   ve3brl

Absolutely!  Any "PR" version of any tetrode will be  a much more rugged version of that tube.   Much more rugged  grids and screens, not to mention plates. It should last a lifetime.

What makes the "PR" version of a tube more rugged?

In spec sheets that I have studied, I don't see any difference (i.e. - plate dissipation is the same, for one thing) except for the fact that pulse service ratings are included.

What am I missing?

Hi,

The "PR" version of a tube is mechanically identical to the non "PR" version except that it has gone through additional electrical testing to ensure the high voltage stand off required for Pulse Radar service among a few other tests.  You will notice a different set of specifications on the PR tubes data sheets since they were tested for specifications required for radar service.  Tubes, like many solid state devices today, had their final specs determined after manufacture.  For our service, you will not see a difference in a PR tube from a non PR tube.

Chuck,

That is exactly what I thought was the case.

Thanks!

It has been said that the pulse rated versions of ceramic tubes have different spacings between electrodes...  3cx800 vs. 3cpx800.

Dunno, don't have the calipers anymore, and probably couldnt see them if I did.

--Shane

PR tubes are tested at higher voltages. A friend worked on a laser that used 3-400s.
They were tested at some real high voltage for 24 hours if I remember. He told me sometimes he would get new tubes with small holes blown in the plates. He told me they worked great. I suggest there could be X RAY issues that high voltage.

I believe I have seen 4PR1000s with mechanically different plate structure (more rugged) than the run of the mill version, I know I have seen 4PR400s with graphite plates. A number of decades ago I happened upon a few type 284 tubes which were surplused out by Raytheon from pulse modulators used by ABM missle radar guidance systems, remember the ABM treaty with the Russians, this instantly created a lot of surplus ABM radar gear. The 284 looks like a 4-1000 as far as the base and bottle go but the plate structure is enormous and made of graphite, the filament current is slightly higher than a standard 4-1000, I also snaged a 294 at an ancient hoss traders flea market which is very similar to the 284, perhaps even more rugged. Tim HLR once tested a 284 in his 4-1000 rig when it was still alive and ran some incredibly high plate voltage on it, IIRC he killed the tube when he had an arc over from the plate through the bottle to an external ground point which unfortunately caused the tube to lose its vacume.

Yes there are some very heavy duty versions of the 4-1000 out there that were originally intended for pulse modulator service.

284 needs 36 amps to light it up if I remember.