IBM 5120 power question

From: Stan Sieler <ss_at_allegro.com>
Date: Sat Nov 20 14:05:42 1999

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.
...
> Getting back to the 5120. You mention a lot of wiring options on the PSU.
> Are these described anywhere (possibly silk-screened onto the PSU
> chassis)? Or how do you know there are various ways to wire it?

No descriptions, no documentation. Based on experience with HP
equipment of the mid/late 70s and early 80s, I was hoping that the
power supply might be somewhat universal.

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
switch to display internal registers (instead of the normal "user" screen),
you get the register display apparently uncorrupt, about 95% of the time.

So, I'm going to examine the memory connections first (the video display
circuity seems to work for the register display, and the user screen
varies over time). I can compare some things to a working 5110 here,
luckily.

thanks,

Stan Sieler

Stan Sieler sieler_at_allegro.com
www.allegro.com/sieler/wanted/index.html www.allegro.com/sieler
Received on Sat Nov 20 1999 - 14:05:42 GMT