Installing an led on a vintage mxr chorus pedal

First thing to ty is to try it using two 9 volt batteries as a test to see if lights work.

I ASSUME that you are NOT trying to use the pedal in the external effects loop (send and return) as the levels are not compatible. The pedal must be between the guitar and the inout of the amp.

Beyond this I would open the unit and look for something loose or broken where the blue LED is located.

It sounds like the bypass contacts on the pedal are not working... this may be right in the pedal switch itself. With unit in off position, use an ohmmeter to check continuity between in and out cable tips.

The battery is being shorted by something. It is impossible for me to guess what without looking at it. If the pedal is brand new, take it back for warranty repair/replacement. If you bought it from somebody, you bought THEIR problem... they likely knew about it. If this is the case, look for a pinched wire from the battery lead... make sure it is not backward. If you can't see anything and cannot get a refund, open the pedal. Look for a problem where the 9 volt adapter plugss in. Broken jack, etc. Look for evidence that somebody has taampered with the insides. Of course look for foreign debris.

Chances are the switch itself is defective... Either the toggling mechanism in it is bad or it has excessive contact bounce. Replace the switch.

I don't know what you mean by "DC Brick"...

The MXR Stereo Chorus unit requires a special 18 Volt power adapter. The common 9 volt pedal power adapters will NOT work with this device. If you have batteries in the unit, when you plug in an incorrect adapter, the unit disconnects from the batteries and the caps discharge so the light will fade.

You will need to use: ECB-004 18-volt AC Adapter Best to use the manufacture's exact device for this one.

My first guess would be that the zener diode is probably shorted. Also check the 2N4125 transistor for a short. Start there and update this with your results.

Dan

Make sure power voltage is adequate. If using a battery, the LED will light LONG after the batteery is beyond usability.

sounds like a switch contact problem, try some surgical alcohol. (for the MXR not for you!!!)

If you are using battery power, just because the LED lights doesn't mean the battery is adequate. Check the battery voltage.

If you are on adapter power, make sure any bypass switch is in right state. Also occassionally someone gets the in's and out's cables backward... that can do it!