Posts: 909
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Joined: Jan 1970
I don't remember a discussion about voltage converters in the 48 or 49. What frequently comes up is that the PMOS machines (Classics, Woodstocks, ?Spice?) all have blocking oscillator-transformer DC-DC converters (not unlike the vibrator supplies in vacuum tube car radios!) that generate +6V and -12V for the logic and (I think) +4V for the LED display or drivers. I know there isn't anything on the Voyagers that looks like a charge pump, like an IC with several caps attached. Nowadays, "regular" CMOS runs at 3V and I think I've seen special purpose CMOS chips specified to run at 1V (maybe rather slowly?) I've been under the impression that NMOS and CMOS chips have internal charge pumps to generate "substrate bias".
I was amazed, while rebuilding my HP67 card reader, to find that the motor only draws 13 mA (no load) from the 3.75V battery.
Posts: 1,162
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AFAIK there is no charge pump (or other step-up PSU circuit) in any Voyager. Certainly the voyagers I've worked on don't have one, and it appears that the 2 chips
in early Voyagers (Nut CPU and R2D2) run driectly off the battery. In fact there are only 3 discrete components in such machines -- the LC 'tank' circuit for the CPU clock and a capacitor connected across the
battery terminals to preserve the memory while you're changing the batteries. Also, I seem to recall reading that the Nut CPU in the voyager differs from the one in the HP41 in that (amongst other things) the one in the Voyager is designed to run
off a lower supply voltage (which would seem to be the battery voltage).