I put in enough 65's, 50's, 75's, 155's, etc. and related gear. Been a
long time but I used the fan rotation to tell if the phases were in
phase. Might have been single phase and if one of the phases were off
they spun the wrong way. But I got burned on this in Sao Paulo back in
the late 70's.
Then I did use it there later on to heat up the core array in a 2365
that had traveled to Brazil in an unheated, mildly pressurized cargo
hold. The epoxy had to be warmed up a bit top get rid of a bit error.
IBM back then wasn't happy forking over the part if they could avoid it,
given the cost that went against the branch office for the array.
Miswired the fan to let the array warm up. Also, I might have made a
slight engineering change while I was there to pick up an unused SLT
circuit on another gate. Tough to get parts....
Fans.
Doug Fuerst
Principal Consultant
BK Associates
718.921.2620 (O)
917.572.7364 (C)
d...@bkassociates.net
------ Original Message ------
From: "William Donzelli" <wdonze...@gmail.com>
To: IBM-MAIN@listserv.ua.edu
Sent: 22-Jun-20 15:09:50
Subject: Re: 3 phase power question for the gray hair group. :-)
Yes its true, but before you let a disk spin backwards, you checked the
fans in the logic gate, they were 3 ph too. Depending on how they spun
(clockwise or counterclockwise), you had the phases corrected. I never
spun up a drive that went backward using that technique.
And if it was say a 2365, or a 2860 or 70, it would power up just fine,
then get a thermal since the fans were spinning in the wrong direction.
Are you sure about the fans in the gate being three phase?
Standard practice for IBM (or pretty much every other computer
manufacturer) was to use single phase fans, just tied across the
phases in a nice balanced matter.
Don't make me break out the Big Blue Binders...
Also, if I could post an image to this list, I would show what a
standard IBM phase rotation sensor looks like. I have a box of them.
They are basically just relays with three windings on the core, and
unless the phases are hooked up properly, they will not throw - all
the magnetic fields have to line up.
--
Will
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