Looking for VAX6000 items

Paul Koning paulkoning at comcast.net
Wed Jul 14 08:54:55 CDT 2021

> On Jul 14, 2021, at 7:43 AM, Brian Roth via cctalk <cctalk at classiccmp.org> wrote:
>> Interesting. Were the power supplies 3 phase input? Like you I have 
>> noticed that most pdp and vax gear just pull 120 volt legs off the 3 
>> phase to balance power loads. So you can run them on a couple of 120 
>> circuits. Outside of say the RP07 (which is a real 3 phase motor)
> The 6000 is not like that. After the inlet box the three phases go to the power conditioner which has a 3-phase thyristor controlled rectifier. From there its 300v up to the regulators. I remember my 11/780 was like you described.

That helps.  It may be that feeding it single phase power (220 presumably) would be good enough, it just means one leg of the three phase rectifier isn't active.  If you're sufficiently below the design max power that should work.  If you really need to drive all legs, and the power conditioner is an adequate low pass filter, a VFC may be safe to feed it; if not, a rotary converter will do the job.

Incidentally. for those who do have disk drives with three phase motors: as the manual points out, the phase order is critical for those.  If you get it wrong the drive will spin in the wrong direction.  You need to catch that before the drive spins up much; the pack might unscrew and/or the heads crash.


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