From: Jim Brain <>
Date: Fri, 17 Feb 2012 00:54:10 -0600
Message-ID: <>
On 2/17/2012 12:38 AM, Jim Brain wrote:
> I can understand that if the 2n3904 was used to drive the TIP29, but 
> the TIP29 was biased on with a 1.5K resistor.  The 2n3904 merely drove 
> the base to ground (.6V or so), thus removing current from the base.  
> Obviously, it would need to sink the 7.5mA through the resistor 
> (11.4/1500), but where was the resit of the current required?
I got my schematics mixed up.  The VIC/64 were biased with a resistor, 
but the PET drive T was biased by the 4401, and the 4401 was biased by 
the 1.5K resistor.

Your original response makes more sense now.


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