From: Jim Brain <>
Date: Fri, 17 Feb 2012 12:32:21 -0600
Message-ID: <>
On 2/17/2012 11:01 AM, Gerrit Heitsch wrote:
> From what I remember, those motors were also meant to be run in 
> battery powered equipment and don't care too much as long as the 
> voltage doesn't get too high.
good point.
>> The +4 keeps the 2sd880 drive, but uses a 7406 for the first stage
> I have a C16 with a TIP29 instead of a 2SD880 and a +4 with a 2SD313. 
> So it looks they again used what was handy...
Hmmm....  In the TIP29 C16, what did they use as a bias resistor?
>> * The 2n3904/2n2222 circuits have a 10K to ground on the first stage
>> transistor base. I assume this weakly holds base at GND until a
>> signal appears. This does not show on the VIC,64. Why not?
> You sure? My schematics for a 250407-board show R3, a 10K resistor to 
> GND on the first stage. And a photograph of such a board also shows 
> that resistor being present.
I was using this schematic:

Interesting that other versions used the darlington arrangement:

While others used the TIP29 without a darlington arrangement:

It appears some have the 10K, some do not.

The use of TIP29Bs in some of the designs without a darlington T to help 
baffles me, based on Bil's response.  TIP29B has better breakdown 
voltages, but still the same small Hfe of 15.


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Received on 2012-02-17 19:00:04

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