[Amps] Equalizing Restistors

[Bill Russell]

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


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
> > >
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Bill Russell