TS-9 led question

[Randall]

I recently did the true bypass mod with the blue 3PdT switch to a friend's TS that already had the LED replaced with a super bright blue one. Seems the combination of the two draws down the battery faster, and as an added bonus the super bright doesn't get dimmer, even down to 4 volts when the pedal sounds like poo. Friend wants the LED dimming feature back. Original one is gone. I want to put in a red one that will dim when the battery gets low, but I understand that the true bypass mod changes things a bit by removing the switching transistor and zener. What would be a good replacement LED for this that will not draw down too much, and will preserve the dimming feature?

Friend is a high end guitar player, and the most sensitive player I know with regards to his gear.

[The Dude]

You could just put a resistor in line with the LED to knock down the current. Then he can still have his fancy blue led. If you run some wires out to a potentiometer first for experimentation, you ought to be able to get a resistor value that does what you are looking for. Otherwise, to my recollection, there's nothing special about the original LED except I believe they had a clear lens. Any standard LED should work.

[Mark Hammer]

Typically, LEDs do not draw more than a couple milliamps; even the older less-efficient ones run at max brightness. Certainly the stock red one that came with the TS-9 wouldn't have drawn very much. Maybe enough to shorten the battery lifespan by 5%, but not enough to produce discernible battery drain.

Contemporary superbright LEDs, like the blue one being discussed, can easily deliver more than enough visibility with 1/4 or less of the current draw that the original required. I can stick a 10-12k current-limiting resistor in series with one and find it more than bright enough.

Recently, I made myself a little LED resistor estimator unit, using a 12-position rotary switch, a bunch of standard-value resistors, and a socket for the LED. The resistors go from 1k up to 18k. I turn the switch up to max resistance, insert the LED to the socket, connect the 9v battery, and turn the switch down until I reach the brightness that I find suitable. Then I select the common value, either a little higher or lower than where the switch is set to, that I think will "deliver the goods".

[hotguit]

Stock TS9 switch has an on board resistor to drop down current to led.
If you replace it with a 3pdt wired for true bypass (with new wires to led) that res. in bypassed and so you must add a res on V+ (usuallyfrom 1K to 4,7K) to compensate things.
Do that and your blue led will work properly w/o sucking so much current
hot

[Randall]

There is a resistor in series already. I think it's the fact that the more efficient bright blue LED doesn't dim when the battery is getting low that is the issue. So I guess any 'normal' red one will do.

[The Dude]

There is a resistor in series already. I think it's the fact that the more efficient bright blue LED doesn't dim when the battery is getting low that is the issue. So I guess any 'normal' red one will do.

There's nothing that says you can't raise the value of the existing resistor if you like.

[Jazz P Bass]

Agreed.
In the working circuit you want to be slightly above the knee voltage of the LED.
Then a drop in the overall battery voltage will dim it.