>Just a note about the HV power transformer in the thunderbolt. It is 4800V
>center tapped at about 500 mills. I have the solid state replacement for
>the HV rectifiers.
>Bill KC2IFR
>
? Sounds good. The CT is an ideal, half-V (c. 1700v)source of current
for the zener string, 800v shunt screen regulator. A 25k-?, 40w R should
drop the needed V.
>At 11:47 AM 3/3/02 -0500, you wrote:
>>Hi again Bill,
>>
>>Just a reminder, you can not use mercury vapor rectifiers with a
>>capacitive input
>>filter. The peak current is too high for them. Solid state rectifiers
>>would work fine.
>>
>>73
>>Gary K4FMX
>>
>>
>>Gary Schafer wrote:
>>
>> > 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
>> > >
>> > > _______________________________________________
>> > > Amps mailing list
>> > > Amps@contesting.com
>> > > http://lists.contesting.com/mailman/listinfo/amps
>> >
>> > _______________________________________________
>> > Amps mailing list
>> > Amps@contesting.com
>> > http://lists.contesting.com/mailman/listinfo/amps
>
>Bill Russell
>
>_______________________________________________
>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
|