Central Electronics
10B
Exciter
My CE-10B model exciter, was interesting
for the refurb job. I got
it without any tubes or coils, just the
unit in its case and nothing else. One good thing about it was that it
wasn't too terribly beat up, so I have
left off the repaint job, until I get a bigger work place for painting
stuff and such.
Anyway, the unit needed tubes, and I got
a manual with it (Original)
along with some of the factory changes
that were recommended to improve operation. Things like moving the
parasitic suppressor to the Plate lead
as opposed to the grid lead. Changing some resistor values and also a
change to improve audio in the unit.
I went to the tube stash and came up
with a complete set for this
unit. Plugged them in and got no output, it
turned out that the 6U8 tube was not mixing the VFO-458 output, I determined this by plugging in a 7285
crystal and placing the unit in CW mode, and getting a 6 watt signal into my dummy load and Bird wattmeter.
If you are going to work on this type of unit may I suggest the following:
turned out that the 6U8 tube was not mixing the VFO-458 output, I determined this by plugging in a 7285
crystal and placing the unit in CW mode, and getting a 6 watt signal into my dummy load and Bird wattmeter.
If you are going to work on this type of unit may I suggest the following:
With a 50 watt slug you can get
"Accurate" low power readings, and since the power output is 5 - 7 watts
I popped mine in and was able to determine that the output section all after and including the 6BA7 was in
fact working. So I took out the 6U8 and replaced it with another, this is a dual package triode/tetrode tube
and the two sections are used in audio and mixing circuits. After replacing this tube I was able to use the VFO
with the unit and get the expected 5 watts on CW again. Well next I did the phasing balance act and went to
AM mode, bummer, no audio, carrier is OK, but no audio. My O'scope told me where the audio was dying
you guessed it, in the triode section of the 6U8. Hum, going to have to start testing these "NOS" tubes to be
sure they work! So drag the tube tester out, set it up, get some COFFEE, and test the next 6U8, oh goody
this one works in the tester and passes (whatever that means) the tester is a Hickok. I put that in the exciter
turned it back on and there you have it, audio, good audio with the pot set at about three notches off zero.
OK, so it works, but I don't think anyone is going to hear a 5 watt signal with all the QRN on the bands these
days. Hum 5 watts, well the HT-33 only needs 2.5 watts to drive it to full legal output, So-o-o! Drag the cable
over to the amplifier, make a bias switching cable and lets fire this thing up. Yep there you go 400 watts of AM
carrier out of the amp and lets get some signal reports!
Here is the bench setup of the 10B and the 458VFO unit. The cable and coil entering the top goes up to the
spectrum analyzer, I was checking the signal suppression as described in the manual, for minimum at 13 Mhz.
That's my E.F.Johnson key I use for CW bench testing, comes with a really long cable so I can walk to the
dummy load wattmeter and read it, my eyes are not good across the room, heh! I even powered the unit into
the E.F. Johnson Thunderbolt, man that is a real nice setup, 5 watts in, set output at 300 for CW and have a
"Ball".
I popped mine in and was able to determine that the output section all after and including the 6BA7 was in
fact working. So I took out the 6U8 and replaced it with another, this is a dual package triode/tetrode tube
and the two sections are used in audio and mixing circuits. After replacing this tube I was able to use the VFO
with the unit and get the expected 5 watts on CW again. Well next I did the phasing balance act and went to
AM mode, bummer, no audio, carrier is OK, but no audio. My O'scope told me where the audio was dying
you guessed it, in the triode section of the 6U8. Hum, going to have to start testing these "NOS" tubes to be
sure they work! So drag the tube tester out, set it up, get some COFFEE, and test the next 6U8, oh goody
this one works in the tester and passes (whatever that means) the tester is a Hickok. I put that in the exciter
turned it back on and there you have it, audio, good audio with the pot set at about three notches off zero.
OK, so it works, but I don't think anyone is going to hear a 5 watt signal with all the QRN on the bands these
days. Hum 5 watts, well the HT-33 only needs 2.5 watts to drive it to full legal output, So-o-o! Drag the cable
over to the amplifier, make a bias switching cable and lets fire this thing up. Yep there you go 400 watts of AM
carrier out of the amp and lets get some signal reports!
Here is the bench setup of the 10B and the 458VFO unit. The cable and coil entering the top goes up to the
spectrum analyzer, I was checking the signal suppression as described in the manual, for minimum at 13 Mhz.
That's my E.F.Johnson key I use for CW bench testing, comes with a really long cable so I can walk to the
dummy load wattmeter and read it, my eyes are not good across the room, heh! I even powered the unit into
the E.F. Johnson Thunderbolt, man that is a real nice setup, 5 watts in, set output at 300 for CW and have a
"Ball".
Here it is with the Thunderbolt in its A.V. Cart.
Did I mention this unit uses
Plug-in Coils?
The CE-10(*) also works great as a driver for the COLLINS KWT-6
RF Amplifier module. I assembled the power supplies for
the plate and screen from parts I had available.
The KWT-6 only requires about 2 watts of drive to get
full power output from the amplifier.
KWT-6 module.
Front.
Rear showing the "Blue Ribbon" connector.
Also the intake holes for air flow.
With the rack mount plate and hinge.
Tube compartment.
6CL6 drivers are under the black tube shields.
Swapped out 4X150 for 4CX250Bs.
Covers 2 - 30 Mhz.
Metering and input tuning
Hoo-Rah!