VAX 780 on eBay

Chuck Guzis cclist at
Mon Jan 3 14:36:27 CST 2022

On 1/3/22 10:58 AM, Paul Koning via cctalk wrote:
> The discussion about 3-phase made me check some documentation.

> I also looked at some CDC 6000 series docs.  Those used 400 Hz 3 phase for supplying the CPU and peripheral logic.  The CPU cabinets also take 3 phase mains power for the  compressors (for the Freon cooling system).  Curiously, the 1964-era 6603 disk drive uses only 400 Hz power.  I wonder if that feeds the spindle motor, or if that was a DC motor?  And the 626 tape drive wants 3-phase mains power.

Are you certain about that?  The '66 document for the Bryant series I

on page 1-3 mentions 280/440 3-phase just for the spindle motor (5 or 10
hp, depending on number of disks).   The hydraulic pump had its own
3-phase motor.  I think the 6603 electronics were 400Hz.   Serious
current draw on those motor lines too--the Series II shows power
consumption draw at 280VAC--somewhere around 50A.

I remember the leak jugs--and the hydraulic fluid that occasionally made
it onto the floor.  An operator at SVLOPS made a dash to take care of a
501 printer and slipped and fell in a puddle of the stuff.  It was funny
at the time...

The old 808/6638 drives, which displaced the 6603, similarly used 280V
3-phase for the 5 hp spindle motor and hydraulic pump and 440Hz for the

The 821 was sort of a double-capacity version of the 808.  Other than
for a few units, it never made it to general distribution, being
rendered obsolete by the 844 disk pack drives.  I recall that CDC
qualified for a lucrative contract by dint of Mike Miller noticing that
one of the 821s had gone offline and doing a 100 yard sprint to punch
the button.  CDC qualified by a matter of seconds.


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