Thunderbolt Discussion

[Bill Fuqua]

Out of 2000 volts DC do you think you will notice about 5 to 7 volts drop 
difference between the solid state rectifiers and the mercury vapor ones? 
The forward voltage drop of a 866A is about 15 volts DC.  Going to Solid 
State would allow you to bypass the filter choke and get a 40% increase in 
B+ but filter capacitors and other components would have to handle it. Also 
you would have to have larger filter capacitance as well. I think we 
discussed this on the AMPS list and the conclusion that going to capacitive 
input filter is not worth the trouble.

73
Bill wa4lav


73
Bill wa4lav


At 01:37 PM 1/19/2005 -0500, Brian Carling wrote:
>Thanks Fred, but I don't own a Thunderbolt.
>The discussion was from the eHam Forum "Boatanchors"
>if you want to pick it uyp there yo can:
>http://www.eham.net
>
>On 19 Jan 2005 at 6:07, FRED HOLNAGEL wrote:
>
> > Replacing the 866's probably raised your HV considerably as well as the 
> rise
> > in line voltage over the years. Maybe you already knwo that. Fred W7PRV
>
> > ----- Original Message -----
> > From: "Brian Carling" <bcarling at CFL.RR.COM>
> > To: <BOATANCHORS at LISTSERV.TEMPE.GOV>
> > Sent: Wednesday, January 19, 2005 4:49 AM
> > Subject: [BOATANCHORS-TEMPE] Thunderbolt Discussion
> >
> >
> > >I thought this exchange might interest you guys...
> > >
> > > N5RVZ wrote:
> > > have restored this amp and the only problem is the HV pops a
> > > fuse every time the HV Plate switch is thrown.
> > >
> > > I have replace the following.
> > > (1) Original 866's with solid state
> > > (2) HV Cap's with new ones
> > > (3) New HV wiring underneath, from HV caps to 4-400's
> > > (4) Replaced existing 4-400's with other sets
> > > (5) Got HV Plate transformer rewound
> > >
> > > I am at a loss what is still the problem! When I disconnect the
> > > HV at the caps from the rest of circuit. I have AC HV at the
> > > end of HV section transformer Coil L101. Doesn't blow the
> > > fuses at this point. Something is shorted after this point!
> > >
> > > Can anybody help?
> > >
> > > Thanks in advance.
> > >
> > > Keith - N5RVZ
> > > = = =
> > > Keith - you should eliminate one thing at a time.
> > >
> > > STEP #1 -
> > > Try disconnecting the rectifier from the HV
> > > secondary of pyour plate transformer. Does it
> > > blow the fuse now?
> > >
> > > If so, then your transformer is bad or your wiring is wrong.
> > > Check all wiring for shorts.
> > > Use an ohm meter to mneasure the resistance of your
> > > transformer windings. Use the LOWEST ohms range.
> > > They should be something ABOVE zero ohms, even if they are
> > > only an ohm or two.
> > >
> > > STEP #2 -
> > > If it all looks OK up to that point, you should
> > > try connecting JUST the rectifiers (no caps or load.)
> > > Does it blow the fuse now? If so, then you might
> > > have some shorted out rectifiers. This could have occurred
> > > because a) They were bad to begin with. OR
> > > b) Because the inrush current to the capacitor(s)
> > > is too much for them. You nee dto limit the inrush current,
> > > because the original circuit had tube
> > > rectifiers that allow a bit of E/R current limitation
> > > through the 866As.
> > >
> > > Let us know how you are progressing after the above two
> > > steps. Consider adding some resistors in series
> > > with your rectifiers. I have never done this but
> > > I hear that some guys add like about 10 ohms at 20
> > > watts to ease things up for the circuit. Remember,
> > > with today's higher line voltage AND the higher plate voltage
> > > you get from the sand state rectifiers, you have probably
> > > increased the plate voltage by 10 to 20% over what it was in
> > > the original application!
> > >
> > > Brian, AF4K
> > > FROM AF4K:
> > >
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> >
>
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