EQD Disaster Transport Junior - popping when stomp switch engaged

Posted by Philtre on Mar 27, 2018; 5:15pm
URL: http://guitar-fx-layouts.238.s1.nabble.com/EQD-Disaster-Transport-Junior-popping-when-stomp-switch-engaged-tp42386.html

Hi, I've built and boxed up the EQD Disaster Transport Junior:

http://tagboardeffects.blogspot.co.uk/2017/12/earthquaker-disaster-transport-jr.html

The offboard wiring is as here - http://tagboardeffects.blogspot.co.uk/2012/02/offboard-wiring.html

Problem:

Works fine except for a loud pop when the stomp switch is pressed on and off. Also, when on, it causes any other pedals between it and the amp to have a pop when pressing their stop switches.

Analysis:

There is a 1M resistor between input and ground in the circuit. I tried adding another 1M resistor between output and ground but made no difference. Also tried disconnecting the LED in case that might affect it, again no difference.

Update - I measured DC voltage at the output. There is about 1.3v DC between output and ground.

Anything else I can try?