PS/2 Interface (was: Wang 300 Calc]
ard at p850ug1.demon.co.uk
Sat Sep 15 17:40:14 CDT 2007
> I dunno, Mike. I'm generally capable of operating most any computer,
> but my eyesight is terrible (and not getting any better with age).
> I'd sure as heck would like the assurance that whatever plug I'm
> sticking into a receptacle at least isn't going to result in "magic
Magic smoke is generally released by :
1) Overvoltage on one or more pins (e.g. connecting an RS232 signal to a
2) Reversing power lines
3) Shorting TTL outputs together (although this may not do any damage if
Since the PS/2 keyboard and mouse interfaces are electrically very
similar, I can see no reason why you'd let the smoke out if you pluged
them into each otehrs' conenctors, unless oyu plug a PS/2 keyboard into
one of thsoe seiral pouse adapaters and then into an RS232 port. But
that's a PS/2 interface, it's an adapter for a mouse that can either be
PS/2 or RS232. Plugging a true PS/2(only) mouse into such and adapter
would do damage too.
I am suprised nobody has complained yet that IBM used a DB25 socket for a
TTL-level parallel port. After all, plugging an RS232 cable in there will
do a lot of damage. Or that HP used a 50 pin Microribbon connector for an
RS232 port on some of their machines -- and evenbrought the sysem power
lines (+5V, +12V, -12V) out on it. Connecting a SCSI device to that will
not be pretty!
I guess it may come down to the unix philosophy in the end. 'We don't
stop you doing stuping things becuase that would stop you doing clever
thigns too'. There may very goof reasons for wanting to connect a device
to an interface connecotr the manufacturers didn;t think of...
Of course no sane person uses mains connectors for anything but mains.
Note I said 'sane'. There was at least one UK audio amplifier (I think it
was a Pye) that used the same type connector -- a 2 pin Bulgin thing --
for both mains input and loudspeaker output. Swap them round, and you
needed a new output transfdormer. I also once had to repair an infrared
spectrometer where the manufacturers had used such a Bulgin mains
connector for the analogue output signal. There was no other mains
connector on the electronics box, so the operator had, not suprisingly,
connected mains to that. In factm the electronics got its mains supply
down a multi-core cable (also carrying motor control signals, etc) from
the optical unit (which did have a mains cable). Needless to say applying
mains ot the output let some smoke out (but suprisingly lttle -- I think
one resistor was burnt out).
> smoke" (see my earlier comment on wall wart perversion) even if I
Hmmm... I can see both sides to this.
On the one hand, it's a very bad idea to use the wrong PSU ('wrong' in
voltage, or polarity, or...). So having unique connectors that only fit
the right device would seem to be beneficial.
But ther other side is that wall-wrts get sepearated from the devices
the power. They may fail. And they're often mains-voltage-specific (a
problem for Europeans wanting to use US stuff...). Some years ago, I
bought one of those packs from Maplin of the 16 most common power
connector 'tips' and a cable with a moudled socket on the end to take
them. The other end of the cable I wired to a couple of 4mm plugs to fit
my bench supply. THis has proved invaluable over the years for powering
up units where the original wall-wart is missing or can't be used.
So I can see the beenfit of a stanard connector too, one that I can match
up with one from this kit.
Also, wall warts fail. Often the output cable fractures internally, close
to the moulded connector. If you can't get the connector, you may be
stuck trying to get a new wall-wart. Try that for a 20 year old unit
On the whole, I guess I'm in favour of standard connectors (2.1mm
coaxial, 2.5mm coasial, maybe 2.5mm and 3.5mm jack plugs), but giving the
power requerements and polarity on the unit iteslf somewhere (either on
the nameplate label, or on the silkscreen of the PCB inside, or...). Not
in the manual only, as that can get lost too.
> didn't quite read the label on the box correctly.
> Making this vintage--does anyone remember the competitions the Eagle
> used to run, taking a bunch of people off the street, presenting each
> with a boxed Eagle (III, I think) and timing them to see how quickly
> they could set the thing up. IIRC, the record was in the sub-one
> minute range.
How pointless, consdiering how rarely most people need to set up a new
computer, compared to doing other things with it.
It's similar to the 'easy to learn' claims of a lot of products. I don't
much care about that. What I want to know is whether, once I've leart to
use it, will it save me time/effort/whatever. I am quite prepared to take
time to learn something that will, and equally, won't waste any time at
all on somethign that won't.
Incidetally, I was once timed to see how long it would take me to
dismantle an ASR33 into the main sections (cover, base pan, typing unit,
keyboard, punch, reader, call control unit) and put them back together
again. I think I got it down to under 5 minutes in each case.
More information about the cctech