Many thanks for the relays to my first post. A couple of points I left out.
The t'bolt is tuned qrid input with one exception. It has a RES input
position which is used for any exciter that will load into a 350 ohm load.
RES means resistor. The is a 350 ohm resistor that terminates the exciter
in this position. It is used in the am and ssb modes. Since modern
equipment will not load into this I was hoping to change this resistor to
50 ohm. This RES position disconnects the tuned input and places this above
mentioned swamping resistor across the grid ckt of the 4-400's. For some
reason this position is NOT used for cw operation. The amp runs class C for
cw and runs class AB2 for am and ssb.
The HV power supply uses the following: 4800 VCT at 500 mills HV
transformer. Choke input filter with a swinging choke. 25 hy at 80 mills to
5 hy at 500 mills. Filter cap is 8 MFD oil at 2000VDC although the hv is
2200 volts! It has a bunch of 0C3's in a separate screen supply for
regulation (4). Ill give more info on the grid supply later (after I figure
it out!)
I would like to either improve the HV supply and increase the plate voltage
if u folks think it would be a good idea or leave the HV as is and maybe
increase or improve the HV filtering. I know if I increase the HV, ill have
to change the screen and bias voltages to maintain the tubes at proper
class of operation. A few months ago I emailed Mr. Measures about this amp
and he said I should change the HV filter to a resonant choke filter for SSB
operation. One more thing........the tubes are at grounded cathode but the
rig does NOT use center tapped filament transformers. It uses 1 transformer
with 2 separate secondary windings, 1 for each tube. At the tube , one side
of the filament is tied to ground and there are 2 .005 caps tied across the
filament terminals of each tube. I always thought this was a bad idea
because this only one side of the filament is at DC ground, not both sides
as it would be with the center tap of the filament transformer tied to
ground. I hope u all got that!!!!
Again folks, thanks in advance...........more to come!!!
One off topic question.................when ppl post anything to this
group, I get the posts twice.......hmmmm.
Bill Russell
KC2IFR
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