[Amps] Equalizing Restistors

[Gary Schafer]

Bill,

It may raise the voltage higher than that. With a choke input filter the DC output
voltage will be .9 times the rms voltage of the transformer. That is assuming that
the supply is loaded enough to have enough of a load for the choke to work
effectively. This may or may not be achieved with just the bleeder resistor in
standby with no plate current. Check to see if the voltage drops a lot from
standby, no plate current, to on but no drive. Just idle current.  If you are
getting 2200 volts at that point then that will be the .9 of the rms voltage of
the transformer. Assuming that it is then dividing the 2200 volts by .9 will give
you 2444 volts. That should be about the rms voltage of the transformer. (it would
probably a 2500 volt transformer?)

Without the choke, just the capacitor as a filter, the peak DC voltage that you
will get should be 1.4 times the rms voltage. In this case that would be 2444
times 1.4 = 3421 volts that you could see in standby. (or 2500 X 1.4 = 3500)  So
be sure that your new filter cap can stand that much voltage.

I usually figure that the voltage under load with a capacitor filter will be about
1.25 times the rms voltage as a rough estimate. That would leave you about 3055
under load.

Yes you will probably need to change the bias voltage and maybe the screen voltage
depending on where it was to start with.

73
Gary  K4FMX


Bill Russell wrote:

> Richard,
> If I understand you, I can remove the swinging choke leaving just the 25mfd
> cap as the hv filter. If the high voltage then rises to about 3kv instead
> of the normal 2.2 kv, I would have to change the screen voltage and the
> grid voltage proportionally to maintain the proper operation of the 2
> 4-400's. Is this a correct assumption?
> BTW....I understand that the 4-400's would run better with 3kv
>
> Thanks in advance,
> Bill KC2IFR
>
> At 09:07 AM 3/2/02 -0800, you wrote:
>
> > >Thanks for the replies folks. I should have figured the power rating of the
> > >resistors myself......i use ohms law, must have been a "senior moment"!!!
> > >As for the swinging choke input filter, Im stuck with it unless I
> > >completely re-do the whole Thunderbolt. If I go to a capacitor in put
> > >filter, the HV will rise and this will cause all sorts of headaches I
> > >think.
> >
> >€  Switching to C-input and removing the swinging-choke should raise the
> >anode-V to about 3kVDC, which is c. the same as a SB-220 and TL-922.  My
> >guess is that the extant tank components will withstand the increase.
> >
> > >My main reason for changing the hv cap is to increase the
> > >capacitance from the stock capacitance of 8mfd to about 25mfd to help the
> > >regulation on ssb.
> >
> >€  To compensate for the transient unregulation produced by rapidly
> >changing current on SSB/CW through the swinging choke, it might take
> >considerably more C.  I would start off with c. 0.1F and check it with a
> >DC 'scope.
> >
> >
> > >Any other suggestions will be greatly appreciated.
> > >
> > >
> > >
> > >Bill Russell
> > >KC2IFR
> > >
> > >_______________________________________________
> > >Amps mailing list
> > >Amps@contesting.com
> > >http://lists.contesting.com/mailman/listinfo/amps
> > >
> >
> >
> >-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
> >www.vcnet.com/measures.
> >end
>
> Bill Russell
>
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