Thunderbolt Discussion

[Brian Carling]

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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