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. > > >> http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/c116-251239-1.gif >> >> >> 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: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/250469-rev.A-left.gif Interesting that other versions used the darlington arrangement: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/251138-2of2.gif While others used the TIP29 without a darlington arrangement: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/251469-2of2.gif http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/252278-2.gif 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. Jim Message was sent through the cbm-hackers mailing listReceived on 2012-02-17 19:00:04
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