Information is provided for purposes of entertainment only. I am not and cannot be held responsible for any harm you may or may not do to your computer, based on information obtained from these pages.
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After
working on a cathode throbber shown on bittech(www.bit-tech.net),
the pinout and voltages of the G4 front panel board connector seemed to
make sense. The principles of one particular electronic component that
all of us have come to love fit perfectly as a simple solution...
Apparently, the pin to the left of the common ground (pin 6 on Diagram
1), is a perfect voltage to use in conjunction with a transistor, and
the 5V power pin (pin 9 on Diagram 1), to produce current to drive an
LED while the machine is on.
Diagram
1
To
better explain, transistors( such
as the Power switching transistor TIP 3055)have three pins. The first
is the base which when supplied with a small voltage will cause current
from the second pin (the collector) to be carried over to the third pin(known
as the emitter). Transistors have other applications such as amplification,
that you don't care about;D
By connecting pin 6 to the base of a TIP 3055 Transistor, pin 9 to the
collector, and wiring an LED in parallel with a small resistor connected
to the emitter, you now have a working LED for your ATX case...you could
also create your own front panel board, should you be building a complete
Mac and not want to pay $250 for the totally unncessary original.
I
actually started to go overboard building a throbber for the front panel
LED, when I decided to test whether or not the throbbing behavior of the
Gigabit and higher series logic boards was based on the logic board or
the front panel board...and guess what...
It's a feature of the logic board! The voltage
on pin 6 is normally +0.463V, and the emitter, +0.412V, however, when
the computer is asleep, the base voltage cycles from ~+0.36V to ~3.6V
which in turns cycles the emitter from ~+0.31V to ~3.1V. This causes the
LED to throb continuously. Another feature, the error flashes, are also
present.
Now I bet you really think that board is useless;D
You
don't need to wire a NMI (Program) switch if you don't want, as I've found
holding down the power button while booting will initiate the same result
(useful for firmware upgrades). I have pin 2 grounded as is the standard.
Here are some pictures of the small adapter I created to interface with
the Lian Li power and reset switches as well as the LED, and a simple
diagram to go from....I don't want to leave it like this for one since
it's pretty sloppy, and two since it was the prototype and I'd rather
have a board set in the front of the machine.
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Interface Board - Sloppy Non-Technical Diagram
I am going to be placing a resistor connecting pin 6 to the base to limit current, so I would recommend you do so as well...I have not had a chance to test, so I have not determined a good value for it. Just to ease anyone's minds though, I have been running the current setup for over a month with no problems. You also don't need to use a TIP3055 as it is much more sturdy then necessary
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Interface Board - Bottom View
Standard RadioShack project box, strip board, TIP3055 Transistor, two
10 pin front panel connectors from gigabit boards (don't ask;D), some
100ohm resistors, and an IDE cable hacked to 10 pins. There's a linear
IC socket in there that doesn't need to be so don't be worried about it
getting "complex"...lol
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Interface Board - Top View
Notice the resistors and the power led...the hd led is hooked up to the
same pins as the power led...why have one, when you can have two.
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Videos
Normal Power
Sleeping
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Information is provided for purposes of entertainment only. I am not and cannot be held responsible for any harm you may or may not do to your computer, based on information obtained from these pages.
