[Heathkit] SB-200 and 572B to GI7b conversion or new 572B's ??

[John L.]

John - if you decide to stick with the 572Bs, use Taylors - at least the filaments
wont collapse when they are mounted sideways. Cant advise you on the rest. BTW are
you sure the tubes are gone, and not a filter cap or diode in the power supply?

wb4mnf wrote:

> This would be a one for two swap or a 2 for 2 and dispense with the
> anode blower???
> -bob
>
> John Peters wrote:
>
> > Hi All,
> >
> > Just got a SB-200, in working order but tubes are lazy, only 300W out with
> > 100W drive. So I need new tubes, there are a few options, buy a pair of new
> > 572B's
> >
> > Which ones are preferable ??  Taylor or Svetlana ??
> >
> > Or should I convert the PA to a pair of GI7b's it seems others has done this
> > before.. I have a bunch of these tubes laying arround, they are much cheaper
> > than the 572B's and more solid too, but need more air so the PA will get
> > noisier. More gain, and a pair will last for ever in this configuration.
> >
> > Is this done before ??? And how should I make bias ?? Real GG design or like
> > with the 572B's with 200pf to Gnd and make a DC ground via some resistors (33
> > Ohms with the 572B's) to get the right Bias current..
> >
> > any info is very much appreciated,
> >
> > 73! de John PA5MS
> >
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