>
>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.
// Good idea.
>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.
// Class AB2 is not linear with a grid driven 4-400. Class AB1 is
linear.
>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.
To run optimally in Class AB1, it takes c. 800v on the screen and much
more anode potential than 2kV.
> 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.
// A swinging choke can not be resonated, so running C-input filtering
might be best. This would require nore C at more V, so electrolytic caps
would be a good solution. V-out on SSB should be c. 3k.
>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!!!!
// Henry and Kenwood do essentially the same thing. If it works, why
fix it?
cheers, Bill
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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