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HP Forum Archive 08

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Voyager series power supply...
Message #1 Posted by WigglePig on 17 May 2002, 5:38 a.m.

Hi there...

Looking at my newly acquired HP15c, my mind recalls a discussion on this list (some while ago) where the power supply of the 48/49 was discussed; these calcs have a ?charge-pump? voltage step-up to run the Saturn/Yorke off three AAA batteries.

Is there a similar arrangement in the Voyager series calcs? If so, then it must be incredibly efficient as my 15c only just requires its first new set of batteries (calc made wk 33 1985)!

regards

WigglePig

      
Re: Voyager series power supply...
Message #2 Posted by Ellis Easley on 17 May 2002, 6:01 a.m.,
in response to message #1 by WigglePig

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.

            
Re: Voyager series power supply...
Message #3 Posted by Spice_Man on 17 May 2002, 1:34 p.m.,
in response to message #2 by Ellis Easley

Did HP manufacture the motors for the card readers?

                  
HP 67 card reader motor
Message #4 Posted by Ellis Easley on 17 May 2002, 2:53 p.m.,
in response to message #3 by Spice_Man

Mine says "escap (R) - Swiss Made"

                        
Re: HP 67 card reader motor
Message #5 Posted by Dave Hicks on 17 May 2002, 3:09 p.m.,
in response to message #4 by Ellis Easley

There's a bit more info here.

      
Re: Voyager series power supply...
Message #6 Posted by Tony Duell (UK) on 17 May 2002, 5:40 p.m.,
in response to message #1 by WigglePig

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).

            
Re: Voyager series power supply...
Message #7 Posted by WigglePig on 31 May 2002, 4:08 a.m.,
in response to message #6 by Tony Duell (UK)

Aha, that answers my question...thanks for that. I had wondered how the $%^" HP had managed to make some sort of volt-converter that was so darned efficient that the batteries last for such a long time.

Regards, and thanks for your time...

WigglePig


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