On Wed, 26 Jun 2019 13:41:49 -0400, Paul wrote:

Can you add a resistor or something to change the brightness?

Yes, you can add a resistor.

The case wiring has a harness with twisted pairs. There
is always some series resistance in the path to limit
the current. (Because making a precise regulated voltage
to drive the LED with a voltage source would cost too much
to do.) The resistor helps limit the current flow. 20mA
is a typical design value for operating current for T1 3/4
LEDs (or so). YMMV. Check datasheet.

What datasheet. I bought a pack of them on Ebay for $1.50, postage
included.


The following diagram
is simplified so only the concept is present.

Mobo +5V ---- Rseries ------------------------- LED-FP
GND---------------------------------------

You can either pull the panel assembly from the case
(could be a small PCB that is removable) and add
an additional resistor there.

There's no PCB in the front panel. The wires run from the motherboard
directly to the LED, using small connectors at the LED housing. I will
have to cut the positive side and patch in a resistor.



In any case, you want this.

Mobo +5V ---- Rseries ------------- Rseries --- LED-FP
GND---------------------------------------


First you had one Rseries, now two. I don't get it.



If you're brave, you could certainly change the
resistor on the motherboard, but it would be SMT
and you'll need skillz to remove.

I have some skills, but I won't risk a motherboard to fix the computer
case LED.


Putting the resistor in the wiring harness
would work. You need shrink wrap (Polyolefin tubing)
to do a neat job and insulate the work. Electrical
tape is a no-no (a gooey mess).

I'd try and do it at the front panel PCB, so the
job is neat and tidy.

That's what I'm thinking. But I don't know what resistor value to try.
Any ideas?