Every guitarist playing electric guitar will at some point encounter the legendary Tube Screamer by Ibanez. Probably the most copied pedal on the planet. Everybody who tried or regularly uses an original TS will also know, that the LED of the pedal is really weak. So weak that you often can’t really tell, whether or not the pedal is turned on or not.
There is an easy fix. The LED can be replaced by a brighter one. But you have to pay attention on the efficiency of the LED you choose.
If we take a look at the schematic of a TS808 (source: electrosmash), we can see that the LED is actually part of the JFET-based bypass.
Resistor R31 (36k) acts as protective resistor for LED D9 and also biases Q7. However, 36k is a really high value for an LED pre-resistor. Hence the LED is very dark. Replacing R31 by a smaller value (e.g. something less or equal than 1k) would make the LED brighter, but it would also change the bias point of Q7 and hence influence the characteristics of the JFET bypass.
The Right LED
What you’ll need for this to work is a high power, high efficiency LED with a certain “brightness”. The specs of an LED will tell you how bright an LED actually is. The brightness is mostly given in milli Candela (mcd). I can’t give you an exact number, but for your convenience, I’ve tried a couple of LEDs. The following list should help you narrow it down.
|red||5 mm||11000 mcd||too weak|
|yellow||5 mm||14000 mcd||too weak|
|white||5 mm||36000 mcd||good|
|green||5 mm||39000 mcd||perfect|
I was really happy with the green one, so I kept that one.
Replacing the old LED
Replacing the old LED is fairly simple. However, you do need some soldering skills. But the good news is: The LED is not soldered to the actual circuit board, but onto a small modular board screwed onto the chassis of the pedal.