RK05 spindle pulleys - trade 50Hz vs 60Hz?

Paul Anderson useddec at gmail.com
Wed Jul 25 23:21:53 CDT 2018

I can't find my IPB, but the maintenance manual shows there were both 50
and 60 hz  versions made.

I think I've shipped them overseas, but never modified them. I did ship a
lot of RX02 drives overseas, and to properly convert them the pulleys,
belts, and wiring harness had to be swapped. We were always on the lookout
for parts. I still have a few different wiring harnesses around here

BA11-K conversions were also common. I still have interesting stories and
parts about them.

What gets me with the RK05 is how you can swap pulleys without swapping
belts. A few products had pulleys with two grooves, one for 50, the other
for 60. But you still needed a different belt.


On Wed, Jul 25, 2018 at 10:32 PM, Tony Duell via cctalk <
cctalk at classiccmp.org> wrote:

> > There are, however, DEC products other than the RK05 which had different
> > transformers for 50 Hz and 60 Hz. For example, the H771 power supply used
> > in the RX01 and RX02. There were three H771 models, The H771A for 90-132
> > VAC 60 Hz, The H771C for 90-132 VAC 50 Hz, and the H771D for 180-264 VAC
> 50
> > Hz. The H771A uses a transformer rated for 60 Hz. The H771C and H771D
> both
> > use the same 50 Hz rated transformer, with different wiring. The H771C
> and
> > H771D also require one of two different wiring harnesses to cover the
> > entire mains voltage range, e.g., 90-120 VAC vs 100-132 VAC for the
> H771C,
> > or twice those voltages for the H771D.
> IIRC that's a ferroresonant transformer (with a capacitor to resonate one
> of the
> windings to a harmonic of the power line frequency), so it's not
> surprising it has
> to be changed for 50Hz or 60Hz input.
> -tony

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