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

[Julio Garcia]

What is a GI7b ?? Sounds Russian.
And how is it compatible in a SB200?  Socket changes?

Julio




On Sun, 27 Jan 2002 14:24:10 +0100 John Peters <pa5ms@qsl.net> writes:
> 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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> 
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