In a message dated 11/7/01 6:52:15 AM Eastern Standard Time, KG6DV@cs.com
writes:
>
> I found a very clean SB200 I couldnt resist. While checking this amp out
> I
> found an interesting situation, High filament voltage. The SB200 has no
> separate filament transformer. It uses one transformer with three
secondary
> windings. I have always put filament variacs in all my homebrew amps but
> they
> all had separate filament transformers. The filament voltage on this amp
> measures 7.25 volts vs the 6.3 volts required by the 572B'S. Considering
> the fact that this about 15% higher than specs, Im not comfortable leaving
> it
> that way. Is this a common problem with the SB200'S ?
> Any suggestions on how to correct the problem?
>
> Ron KH6DV
>
Ron,
I would suggest using nichrome wire in series with the filament leads from
the transformer to reduce the filament voltage to the proper value.
The bottles will last much longer....and with the cost of 572Bs, certainly
worthwhile.
73 de
Dave, WT8R
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