Re: Henry 1002 amplifier, a single 3cx400xx
Hello all,
I just picked up a surplus Henry UHF amplifier, a Henry 1002. This
amplifier is a single tube 3CX400xx, cathode driven on 270 MHz. Also
included was the power supply which is surprisingly small.
This amplifier was designed for pulse rated service in research work.
Anyone else run a similar tube cathode driven or seen the
paperwork/advertisement for this line of amplifier(s). There is another
soon to be mine that is very similar, just on a different frequency
range.
Other small details include:
Input tune circuit: two small variable caps and a 1/2" 1.25 Turn about
3" Long strap from the bnc to the cathode. The caps from a divider, the
high end at the input bnc, the center is one side of the inductor. The
other end of the inductor is at the cathode.
The heaters are brought out separate from the socket box directly
underneath the tube to the adjacent shielded part of the chassis. Ohmite
Z-235's are used after the bulkhead feed-throughs which are 2000M.
The cathode leaves via an ohmite Z-50 choke through a similar bulkhead
cap.
It's interesting that two Z-235 chokes are parallel at each point where
used.
The (tube socket side) heater chokes are 1/4" close wound enameled wire
coils on phenolic type cores and measure about 2.4uH on my Sencore
LC-102.
The heater and the cathode lines are separate runs until the other side
of the bulkhead where one side of the heater is tied to the cathode.
Where does the guideline for the tied cathode to heater explained?
Normally I would expect one to go to ground, but the heater/cathode lead
is the only one close through the negative lead of the HV supply to
chassis through a 200 ohm 20 watt resistor.
Is there a guideline for choosing the physical type of tank circuit, ie
tubular/coaxial vs the strip/strap method? This amplifier has the strip
tank circuit design.
No TR circuit and a novel method of measuring grid current during meter
calibration through a shorting RCA jack/connector assembly on the rear of
the ps.
A single transformer supplies to a doubler and the HV leaves the ps
through coax cable and MHV connectors. Bias is set by a 1N2808 TO-3
package zener when not cutoff during warmup.
It was pretty hacked up when I got it, so I'll finish cleaning it up and
checking the parts over... then it's show time after I move it down to
224MHz...
I'd appreciate any thoughts about the tube, the amplifier and what I can
expect from it after the repairs and mods are done. I would prefer to
leave it cathode driven.
thanks
skip may wv6f
nospam4me@juno.com
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