Hello Gang,
Went to the swap meet last weekend in Mesa AZ. and came home with a pair
of medical pull 4PR-1000 tubes in what appear to be like new condition. (One
is an EIMAC and the other a Triton and both have early 98 date codes.) I
was told they were pulled due to the time in service, not performance so I
am hopeful. The price was right even if only one is working. If both are
NG then I have a nice pair of bookends or lamp basses. ;>} I'll remain
optimistic for the moment.
First order of business is to find someone who can put them on the air
and check them out or a commercial tester who can test them to see what
condition their condition is in. (OPPS, flashback to '60 rock.) ;>} If
anyone has info either
option, let me know.
Second item is sockets and chimneys. Two would be nice but one of each
will do for a start. Let me know what you have and what you want/need for
them. A trade is ok by me as I do have a collection of stuff myself.
Third item is knowledge. Once again the collective wisdom of the group
is requested as I really don't like reinventing the wheel and for some of
you this is old hat. Here is what I am curious about...
1. I remember from comments on this reflector that the 4-1000 takes a bit
of drive to get full output and it likes lots of HV. Something like over
130 watts of drive is not unusual especially when you get to 10M. As I
recall 4KV is preferred to say 3KV and I see from the one spec sheet I have
that it can use up to 5.5KV under 30Mhz. I am thinking that 4KV is probably
a good place to start as it is doable with what I have on hand. I question
all this because I will most likely have only 100 watts or less drive
available.
2. IF in GG service they are tough to drive to max legal smoke with 100W,
then how about Grid Driving it and running AB2? Looks like it only needs
something like 14 watts to get full tilt boogie out of the bottle that way.
A switched attenuator on the input could help not cook things or overdrive
the tube. What about matching the input to a solid state output rig?
Switched Pi networks just like with cathode driven ok or does someone have a
slicker idea in mind? Yep, I know I will need a screen supply of something
like 750VDC but that looks a bit academic. I would likely use something
like the English tetrode boards just for the safety factor they offer in
case of an OOPS!
3. Stability. If I remember correctly there was some question to the
stability of the 4-1000/4PR-1000. Can any one comment on problems they have
encountered with this tube in that regard?
4. Matching. I do remember a few of you commenting that there were some
problems with trying to get a good match in the final Pi net because of the
high capacity in the tube. I thought that interesting at the time because
this tube was used as an FM broadcast amp and has a max usable frequency of
up to 110Mhz.
Any tricks or methods that would make my work easier here would be nice..
5. The missing program...Somewhere I had been given/found on the net, a
simple program. As I recall, you put in the type of tube,
(triode/tetrode/pentode), the class of operation, the Q of the tank, the
plate voltage and current and specified what frequency you wanted the values
for and it and if it was a Pi or PiL net and hit enter. It would give you
the values of all components in the tank circuit. You just went from freq.
to next freq. and it would add them to the list. When done, you just titled
the file for what ever you wanted to call it, (Example= 4-1k tank
specs.txt) and away you would go. VERY NICE PROGRAM. Somewhere it has been
lost to the software gremlins. DOES ANYONE RECALL THIS LOVELY BIT OF
SOFTWARE AND KNOW WHERE I CAN GET IT AGAIN! My searching the net has gotten
close a few times to something a bit like it but not what I recalled.
Final comments.
I am hoping to make this my first real long term amp. A solid beast
that will do max legal amateur output with no sweat. It will laugh at
contests, broken antennas, miss tuning and operator error all without
TVI/RFI. QSK at 35 wpm? No problem. Fast warm up? Sure. Silky smooth
tuning with repeatable settings from a chart? Of course. AND be driveable
with less than 100w (maybe down to less than 20watts) on any band.
OH, and did I mention that like most projects this one is also on a
limited fairly long term budget? Yep, after two years of working E-Bay and
the swap meets I have a fairly good start of parts but it is time to make
the final plan to put them all together and make my version of "Godzilla!"
So break out your thinking caps, get a cup of your favorite beverage to
rethink your past 4-1000 projects and give me your best shot. What did you
do and what would you have done differently and why?
Again, in advance I will respectfully thank you for your thoughts and
comments..
Best 73
Mike Baker K7DD
Peoria AZ.
k7dd@qwest.net
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