18 Nov
1999
18 Nov
'99
12:04 p.m.
Hi,
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
enough choices in wiring that I suspect the power supply might already be
capable of being easily adapted to 110/60 Hz ... does anyone have
any familiarity with this system? Otherwise, I'll be visiting
Fry's for something (transformer?).
thanks,
Stan Sieler
sieler(a)allegro.com
Stan Sieler sieler(a)allegro.com
www.allegro.com/sieler/wanted/index.html www.allegro.com/sieler
19 Nov
19 Nov
5:08 a.m.
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20 Nov
20 Nov
6:05 a.m.
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(a)allegro.com
www.allegro.com/sieler/wanted/index.html www.allegro.com/sieler
6:59 a.m.
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8:13 a.m.
On Sat, 20 Nov 1999, Tony Duell wrote:
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
Re:
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. > 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. 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
9:12 a.m.
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2:18 p.m.
On Sat, 20 Nov 1999, Tony Duell wrote:
> > 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.
I never much cared for those drives, Tony. IIRC, there was no way to
remotely unload the heads from the media. The best that you could do
was to power down the spindle motor. Of course, the problem there was
the finite time for the disk to come up to speed when power was
reapplied.
I seem to remember it was an option on a drive made by
a company called
'Elcomatic'. I have a couple of the drives (with 240V mains motors) on my
PC/XT, and I have the service manual _somewhere (but don't ask me to find
it :-)).
These are full-height drives, same form factor as a SA800 or whatever.
One other neat feature is that as well as the track0 sensor, there's
another slotted optoswitch that operates on track 43 and greater. So
these drives don't need the TG43 signal from the controller, which is
handy if you're linking them to a PC.
However, IBM (and a few other companies) made their own drives, so it's
quite possible they did something strange [1]. I could well believe that
they used drives with 24V motors, for example.
I think that a definitive response to Tim's quiz will be quite
interesting. I do not know of any, personally, but...
- don
[1] Although not as strange as a Radiogram I have the
service sheet for.
This thing would run off AC or DC mains, and there were 3 valves that
were only used on DC mains. The radio chassis was a conventional
'universal' set (series-string heaters, rectify the mains to get the
anode supply). You guessed it, the other 3 valves (a couple of 50L6's and
something that would oscillate) formed a 50Hz PSU for the turntable motor.
-tony
10:49 p.m.
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