50Hz vs. 60Hz

[Ian King]

> -----Original Message-----
> From: cctalk-bounces at classiccmp.org [mailto:cctalk-
> bounces at classiccmp.org] On Behalf Of Mike Ross
> Sent: Wednesday, September 23, 2009 9:59 AM
> To: cctech cctech
> Subject: 50Hz vs. 60Hz
> 
> 
> Folks,
> 
> I'd appreciate some thoughts in general, and on some specific cases, on
> using 50Hz DEC equipment on 60Hz power, since I've started processsing
> and restoring a large quantity of DEC equipment I've brought over from
> my UK storage to the USA:
> 
> 1. Thinking about old DEC logic power supplies in general (pdp-8, -11,
> -12, -15 etc), is there liable to be any problem with using equipment
> sold in 50Hz countries on US 60Hz supplies? Obviously output voltages
> would be checked as a matter of course anyway!

If you're looking at linear power supplies, take a look at the badging on the transformers.  According to our EE here, many if not most were actually rated for 50/60 Hz operation.  They run a bit warmer at 50 Hz.  Switchers tend to be very accommodating, AFAIK.  Most of them seem to just rectify the AC and feed the switching circuitry with it.  

> 
> Equipment which uses motors is, I would have thought, liable to be more
> of a problem, for instance:
> 
> 2. Tapes. Would 9-track (e.g. TU45, TU16 etc.) tapes be likely to be a
> problem? It occurs to me the transport speed might be a little off...
> 
> 3. DECtapes (& LINCtapes) : I would imagine they would be less of a
> problem; they're self-clocking and practically indestructible - you can
> almost read a DECtape with a toothbrush, some tinfoil, and a set of
> bicycle pedals! Thoughts?

One thing that really helps with DECtape drives (at least TU56) is that the motors are not run off the AC line, but from DC and internally generated waveforms.  
> 
> 4. Disks. Biggest problem I would imagine. RK05s I know have different
> motor pulleys - they're stamped 50Hz or 60Hz. I would imagine running a
> 50Hz unit on 60Hz wouldn't work, the heads would never load because it
> would never be detected going at the correct speed. And even if they
> did load there might be air bearing issues due to incorrect speed. I
> have around 7 or 8 50Hz RK05s, but only 3 60Hz, so... does anyone have
> any spare 60Hz RK05 pulleys, or motors with 60Hz pulleys attached? What
> about RL and RX drives? Similar problems?
> 
> Many thanks for any advice
> 
> Mike
> http://www.corestore.org
> 
> 
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