> Has any of you tried some easy improvements to the old Johnson
> Thunderbolt?
> I just got a parts unit that I plan on restoring but I may not make it
> original. One thing that
> strikes me is the low plate voltage and the small diameter wire on the
> roller inductor.
> I suspect the output component ratings voltage and current may be a
> limiting factor.
> A full wave bridge rectifier would be an easy way to increase plate
> voltage,
> if bypass and plate tuning capacitors allow. However many of these old
> transformers do not like
> having their center tap floating at high potentials.
>
> //You'd better be prepared to make a variety of changes, I would think,
> Bill. As an ex-T-bolt owner (about 1969 to 1977 or so), I recall the HV
> filter cap was just a single oil-filled (original was PCB-laden, new ones
> shouldn't be) cap installed horizontally beneath the chassis, and there
> wasn't much room for anything bigger or an array of 450V electrolytics as
> is the common approach today. Since the HVPS had a choke, the cap didn't
> need to be very big. It was also only rated 2000WVDC, right on the edge
> of failing from the start, as I recall. When I replaced my cap, I went to
> a 2500WVDC unit for a tad more margin.
>
> //IMHO, the T-bolt is far more valuable as an antique collectible than it
> is as a daily-use amplifier, and I'd hesitate to change it much. I even
> left the gas tube rectifiers in place, ultimately, to maintain its
> collectible value. I'm very glad I did, since when I sold it I received
> far more than I originally paid for it, and other than "repairing" things
> that failed, I didn't change anything.
>
> //Agreed the T-bolt was pretty much a waste of a pair of 4-400's and never
> ran nearly the power those tubes are capable of!
>
> -Steve, WB2WIK/6
>
>
>
> 73
> Bill wa4lav
>
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