MXR 10 Band Equalizer: Dim LED Mod M108S

READ ALL THE NOTES BELOW BEFORE ATTEMPTING THIS MOD!
R37, R13 are the 0805 resistors (***R46 is a 1206 size) you need to change from 2.2 kohms to 33 kohms. I did try 47 kohms which works as well but there was not much of a difference in brightness between the two.

******UPDATE October 23rd, 2024: A gentleman asked me to mod his MXR with the dim LED mod. I did exactly as I did for my MXR, but was getting a nasty "fizzyness" distortion to the output. R46 operates the two outer volume/gain fader LEDS. They are also the "clipping indicator LEDs." They are tied to the opamp with the negative bias supply and opamp detecting the peak amplitude. Changing R46 POTENTIALLY can cause a fizzy/distortion sound since it changes the current through those LEDs. Thus changing the bias to the opamps. I believe the fizzyness is crossover distortion. I did not run into this problem with my MXR, but it may happen to yours. To compensate, leave R46 at 2.2kohm, purchase alternate 2x3x4mm LEDS, sand them down, and color with a black sharpie to darken them. This solved the issue for the gentleman I modded his MXR. I then put 33k ohm in for R13, and R37, those are switch operated and have no connection to the audio circuitry.

The part# used is below.

R13, R37: https://www.mouser.com/ProductDetail/...

R46: https://www.mouser.com/ProductDetail/...

Transparent (OEM) Lens LEDs: https://www.amazon.com/dp/B0CWKZZ7BP

Frosted/Diffused Lens LEDS: https://www.amazon.com/dp/B0CWKQ4WM7

***This modification requires SMD rework skills and special tools to efficiently change the resistors out. You can do this with a pencil iron, some Chip Quick, solder wick, flux, steady hand, and some patience. Soldering tools used at an FX888D Soldering station with the FX8804 Hot Tweezer kit. Mod for me took about 15 minutes total.

I don't think many would tackle this project at this level because of the difficulty. Many will chose to do the many low tech solutions like tape or black sharpie. Those solutions certainly work well. I could not leave well enough alone needing another electronics project to do, so I tackled the high tech solution.

I worked on revision G0, but the schematic I was able to find is REV E, the LED circuit seems to be the same.

https://www.flickr.com/photos/9289188...

Thank you for watching! Questions please let me know!