Motor generator

Chris Elmquist chrise at
Thu May 6 21:47:24 CDT 2021

> On May 5, 2021, at 10:37 AM, Chuck Guzis via cctalk <cctalk at> wrote:
> On 5/5/21 5:18 AM, Paul Koning wrote:
>> An earlier message commented on the whine from power converters.  I
>> don't know how common this practice was, but at the University of
>> Illinois PLATO system which had a pair of 6500 systems, the
>> motor-generator was located near the elevator machinery in a corner
>> of the building, far from the computer room.  Yes, it was noisy, but
>> no one spent any time in that location.  The computer room was -- by
>> mainframe standards certainly -- rather quiet.  Of course it helps to
>> have liquid cooling, so there weren't many noisy fans to deal with.
> It was the "white noise" from the vacuum pumps in the tape drive banks
> that drove me nuts after a few hours.  After 8 hours or so, I sometimes
> found my hands shaking.  Of course this facility had a very large
> machine floor with several full-sized installations.  Eventually,
> management provided ear protection.
> As far as any "whine"--I vaguely recall hearing a high-pitched whine if
> I put my ear close to the power adjustment panel in a CDC Cyber--but it
> was barely audible.
> As far as the MG sets themselves, I never went there--any noise at
> SVLOPE was drowned out by the fans in the cooling tower.  I don't recall
> where the power equipment at ARHOPS was located.
> --Chuck

We had a room on the ground floor at ETA that housed an MG set that ran the CY205 (and maybe the 835 and 875 too) in the basement.  They had isolated the MG from the mounting pretty well in addition to sound proofing the room because with door closed, you couldn’t really tell it was in there— which was nice because the room was right off the main entry hallway :-)


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