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From: Carlton on 20 Apr 2008 14:02
I have acquired an IBM Intellistation motherboard, however, I am unable
to install it as I don't know where to connect the power and reset
switches. The IBM PCs have a single connector from the front panel to
the motherboard, where as my case has individual wires for the
PWR/RST/HDD etc.. I have checked the IBM manuals on-line, but they don't
detail the pin out of the connector.
Anybody able to help ?
thanks in advance,
Carlton.
From: Paul on 20 Apr 2008 14:46
Carlton wrote:
> I have acquired an IBM Intellistation motherboard, however, I am unable
> to install it as I don't know where to connect the power and reset
> switches. The IBM PCs have a single connector from the front panel to
> the motherboard, where as my case has individual wires for the
> PWR/RST/HDD etc.. I have checked the IBM manuals on-line, but they don't
> detail the pin out of the connector.
> Anybody able to help ?
> thanks in advance,
> Carlton.

Do you have a multimeter ? When you press a POWER or a RESET button,
the switch contacts should be momentarily closed. Using a multimeter
set on the ohms scale, and probing combinations of two pins, you should
be able to figure it out. The multimeter would be set to the ohms
ranges, and 2K ohms or so might be good. You're looking for a
zero ohms reading, when either the POWER or RESET button is pressed.

Say the IBM computer case wiring harness looks like this.

/ RESET
----------+ +-----+
| <--- ohmmeter reads zero, when you find
-------------------+ the right two pins, and you press the button

/ POWER
----------+ +-----+
| <--- ohmmeter reads zero, when you find
-------------------+ the right two pins, and you press the button

+ |\ | -
----------| \|-----+ <--- for this one, you'll need three 1.5V
| /| | alkaline cells in series, plus a current
|/ | | limiting resistor. When the LED lights up,
POWER LED | then you know you're on a LED set of pins.
-------------------+

A LED test circuit would look like this - three alkaline 1.5V cells plus a current
limiting resistor. The LED should light, when you find the correct terminals.
4.5V was chosen as a power source, as most cheap LEDs for computer cases will have
a minimum 5V reverse (PIV) limit, so no damage should result if the polarity
is reversed. Usage of a higher voltage does not carry the same guarantee.

+-------/\ /\ /\ --------------+
| \/ \/ \/ | 10mA test current
| 270 ohm 1/4W or 1/8W |
+ | |
----- | +
--- -----
| \ /
----- \ /
--- ---v---
| | -
----- |
--- |
- | |
+---------------------------------+

Some multimeters have a "high power ohms" test option, which uses
more voltage than normal. Some multimeters can light up a LED,
but very dimly, by using their ohms scale. Not all multimeters
can do it, so the circuit with the batteries and current limit resistor
is more likely to guarantee a test result. The resistor is not too
critical. You could use a 220 ohm or a 470 ohm, and still see something.
Four 1K ohm resistors in parallel, will give you 250 ohms. So
even the crappy selection at Radio Shack can be used.

http://www.radioshack.com/product/index.jsp?productId=2062343

+-------/\ /\ /\ --------------+ Using four 1000 ohm
| \/ \/ \/ | resistors to make a
| | 250 ohm resistor.
+-------/\ /\ /\ --------------+
| \/ \/ \/ |
| |
+-------/\ /\ /\ --------------+
| \/ \/ \/ |
| |
+-------/\ /\ /\ --------------+
| \/ \/ \/ |
+ +
<------- 250 ohms -------->

HTH,
Paul
From: kony on 20 Apr 2008 15:21
On Sun, 20 Apr 2008 19:02:40 +0100, Carlton
<USENET(a)adent.demon.co.uk> wrote:

>I have acquired an IBM Intellistation motherboard, however, I am unable
>to install it as I don't know where to connect the power and reset
>switches. The IBM PCs have a single connector from the front panel to
>the motherboard, where as my case has individual wires for the
>PWR/RST/HDD etc.. I have checked the IBM manuals on-line, but they don't
>detail the pin out of the connector.
>Anybody able to help ?
>thanks in advance,
>Carlton.

We shall assume you don't have the original case for it, nor
the wiring harness from that case, correct?

Do you have a multimeter?

Can we assume you otherwise have a known compatible power
supply (I don't know, could assume it's ATX but since I've
never seen that board...), processor and memory installed so
you can do a simple test? Do you have any spare resistors
by chance? If you did, you could take each pin in turn
while the system was hooked up and ready to turn on,
touching the resistor lead to a pin (only for a fraction of
a second would be needed, don't do it for long) and to the
grounded chassis.

It would turn on when you get the right pin. As for the
reset, once you have it turned on, it'll sit there until you
find the reset pin by doing the same thing. I don't know
what the minimum required current to pull that down
(activate it) would be, so I would probably try a resistor
value around 120 Ohm. Since it limits current quite a bit,
even if IBM had routed a 5V pin to this header (which is
quite possible) it would be better than dead-shorting out 5V
rail to use the resistor.

The trickier part without a multimeter is determining if the
adjacent pins are ground as you have with your two-position
sockets for a standard case, or if IBM had used a common
ground arrangement instead of separate ground for every
function (on/off, reset, each LED, USB if so equipped,
etc.).

Anyway there's probably not much more we can advise on till
we know if you have a multimeter, the original case, etc.
From: Carlton on 20 Apr 2008 17:08
kony wrote:
> On Sun, 20 Apr 2008 19:02:40 +0100, Carlton
> <USENET(a)adent.demon.co.uk> wrote:
>
-SNIP -
> Anyway there's probably not much more we can advise on till
> we know if you have a multimeter, the original case, etc.

No I don't have the original case, but I do have a multi meter and some
resistors. I should be able to have a go, probably tomorrow night.
Thanks for the tips.
Carlton.


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