Carlton said:
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
