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- standard cdrom activity lights
December 28, 2005, 2:51 am
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Re: standard cdrom activity lights
eject the drive tray and pull the tray plate off (if it has
Press in the plastic tabs on the sides or bottom to remove
the remainder of the drive faceplate
Take the cover off the drive... usually 4 or 6 screws.
Pull out the circuit board- might be another 2 or 4 screws
and two or three ribbon connectors, a couple of 2 pin drive
plugs to unplug too. Whole thing disconnects and pulls out.
you'll see on the front of the board, the led is just a
(typically 3mm but rarely 5mm) bi-pin LED bent at a right
angle. Just desolder it and take a pair of wires, solder
thse to the spot on the PCB.
Decide where to take the wire out of the casing... that
dictates how to proceed from here. Supposing you want the
LED power to control a 50 Megawatt laser cannon pointed at
your neighbor's house, you'd probably want to take the two
wires out the bottom left-hand corner (looking at rear of
drive), so it was nearer the right side of the case (looking
at front of case), so it was the shorter distance to the
I suggest positioning the laser on the right side of the
case, since ATX usually has left side panel removable. Thus
you retain access to the system without having to move the
laser canon. If you have BTX or another form factor, your
needs may differ.
Next decide if you want an optical coupling between the
laser canon control circuit and the optical drive (reusing
same or similar enough LED) or to forego the LED for a more
direct electrical coupling. If you can accept LED, it stays
more modular, it is easier to swap out the laser canon
should the need arise, even put it on a drop-down elevator
for safe storage in the basement should you fail to
eliminate any witnesses.
So you have the pair of wires coming out, and supposing the
optical connection, just solder on the LED, and you're
done... after reassembing the drive of course. You might
find it necessary to drill a hole in the rear of the optical
drive casing, and preferribly put in a rubber grommet to
help keep the wire from wearing against the sharp corners of
the casing. If you felt like filing down the corners and
putting a piece of heat-shrink tubing over that portion of
the wire, you could probably do without the rubber grommet.
Another option would be the typical grommet with a lock-tab,
similar to that seen on AC exit, switch wires on the older
AT style power supplies or many appliances with an
If you find you need more (or less, which is doubtful)
current than the original LED driving circuit supplied,
you'll have to trace back that subcircuit on the optical
drive PCB till you hit the current limiting resistor, and
either put another one in parallel or take out the original
and replace with another of suitable value.
Online LED resistor calculators will help you find the right
value resistor, or pair of them if you want to leave the
original in place. Naturally you'd also have to take the
voltage reading pre-resistor to determine how much current
you're trying to drop, and unless you're comfortable fudging
the led forward drop voltage, you'll need the spec sheet for
that as well... or you could just aim low and meaure the
current, figuring it should be somewhere in the 10-30mA
range most often.
Reassemble whole thing, call your neighbors on the phone and
tell them to look out their window, then turn the system on.
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