IBM 5120 power question

From: Don Maslin <donm_at_cts.com>
Date: Sat Nov 20 16:13:23 1999

On Sat, 20 Nov 1999, Tony Duell wrote:

> >
> > Re:
> > > > I just received an IBM 5120, from Germany. The back says 200/210/220 volts
> > > > at 50 Hz. However, opening it up and looking at the power supply reveals
> > ...
> >
> > > Well, I don't know this machine, but I can make some general comments.
> > >
> > > Firstly, it's normally safe to ignore the frequency differnce, at least
> > > to start with. Most PSUs are equally happy with 50Hz or 60Hz. A _few_
> > ...
> >
> > That sounded good, until I read further:
> >
> > > The mains frequency may be important if AC motors (like disk drive
> > > spindle motors) are run off it, since the speed of induction motors is
> >
> > because there are two 8" floppy drives in the same case.
>
> Ah... Most 8" drives do have mains-powered induction motors, so the
> frequency does matter. I've seen reference to the odd drive with a 24V DC
> spindle motor, but I've never seen an actual drive like that (although I
> am sure they exist). If the motor 'looks' like a mains motor, has a large
> capactor can hung off it, and seems to have mains wiring going to it,
> then it's likely to be a mains motor.

The only 24V DC spindle motor that comes to mind at the moment was on
the Tandon 848-02 DSDD half-height 8" drive, Tony.

                                                 - don

> Also, most of the time, the drive spindle motors exist in 115V and 230V
> forms. A few machines always use 115V drives and run them of an
> autotransformer (or the primary of the PSU transformer serving as an
> autotransformer), but many of them expect you to have to have the right
> drive for your local mains voltage. You might well have had to use an
> external step-up transformer anyway....
>
> As to the speed problem. I assume the drives are turning, albeit too
> fast. Normally there were 2 motor spindle pulleys, one for 50Hz and one
> for 60Hz, all other parts being the same. The 60Hz one was about 5/6 the
> diameter of the 50Hz one (the speed of these motors is proportional to
> frequency).
>
> In which case you need to make a new spindle pulley. This is a pretty
> easy job on a lathe -- if you don't have machine tools, try to find a
> friend who does model engineering and who can make you such a part.
>
>
> > I bought a step up transformer and tried powering up the system
> > yesterday. It wasn't a total failure. The monitor displays every other
> > character as a solid white box, and other every character as varying
> > junk (the junk varies while you watch). If you flip the display control
>
> This is almost certainly another fault, not related to the mains
> frequency problem.
>
> -tony
>
>
Received on Sat Nov 20 1999 - 16:13:23 GMT