50Hz vs. 60Hz

[Tony Duell]

> 1. Thinking about old DEC logic power supplies in general (pdp-8=2C -11=2C =
> -12=2C -15 etc)=2C is there liable to be any problem with using equipment s=
> old in 50Hz countries on US 60Hz supplies? Obviously output voltages would =
> be checked as a matter of course anyway!

In general, a mains transformer can be used on a higher frequency 
(sensibly higher, I am not talking about MHz :-)) without problems. A PSU 
that works on 50Hz will work on 60Hz. AFAIK the only change on DEC PSUs 
was for the mains voltage (2 primary windings on the trasnformer, 
connected in series for 230V and parallel for 115V).

The exception is ferroresonant supplies. These have a winding on the 
transformer which is resonated to a harmonic (normaly 3rd IIRC) of the 
mains frequency by an exeternal capacitor. Normally convertiny one of 
these involves a replacement transformer. And DEC did use them/ The 
RX01/RX02 floppy drives, for example.


> 
> Equipment which uses motors is=2C I would have thought=2C liable to be more=
>  of a problem=2C for instance:
> 
> 2. Tapes. Would 9-track (e.g. TU45=2C TU16 etc.) tapes be likely to be a pr=
> oblem? It occurs to me the transport speed might be a little off...

I thought all the magtapes used DC motors with electronic control (in 
which case there's no isssue at all). 

> 
> 4. Disks. Biggest problem I would imagine. RK05s I know have different moto=
> r pulleys - they're stamped 50Hz or 60Hz. I would imagine running a 50Hz un=

YEs. Same with one otuer drives too.

> it on 60Hz wouldn't work=2C the heads would never load because it would nev=
> er 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 50=
> Hz RK05s=2C but only 3 60Hz=2C so... does anyone have any spare 60Hz RK05 p=

Find a freind with an engineer's lathe and get a few turned up? You have 
a 60Hz pulley which could be used to take measurements from

> ulleys=2C or motors with 60Hz pulleys attached? What about RL and RX drives=
> ? Similar problems?

I am prety sure RL's don't care at all. RX's (at least RX01 and RX02) are 
the igest prole,. Not only do you need new pulleys on the spindle motors, 
but the PSU uses a ferroresonat transformer (see above). My be easier to 
find a US (60Hz) unit

-tony