[Amps] Equalizing Restistors

[Richard]

>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
>> > > > >
>> > > > >_______________________________________________
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>> > > > >
>> > > >
>> > > >
>> > > >-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
>> > > >www.vcnet.com/measures.
>> > > >end
>> > >
>> > > Bill Russell
>> > >
>> > > _______________________________________________
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>
>Bill Russell
>
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-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
end