3PDT Switch - confirm my suspicions please...

paulphoenix

So I'm wiring up my footswitch to a DIY pedal kit.

The circuit was working fine when tested with a battery clip and wired straight to the jack in and out sockets. I commenced wiring the footswitch and 9v and LED. the led works fine. the pedal works in bypass when "off" i.e. north plus common. but not when "on" - I get no signal. no ground buzz. no hissing.

So I poked around the switch lugs with my multimeter and find the following weird result when the switch is "on" i.e. south plus common

 

                                              NORTH:                     1                  2                   3

DMM reading north & common:               OL              OL            0.300 @2M settings on DMM

                                           COMMON:                  4                 5                   6

DMM reading south & common:               0.0              0.0              0.0

                                               SOUTH:                      7                  8                   9

surely I should be getting an OL reading between 3&6 if the switch is connecting south to common?

Is my switch buggered?

Sporky

Did you take those readings with anything connected to the switch?

If so then - while they can fail - I would also check elsewhere. Very easy to get a whisker of solder to bridge two tracks or pads.

paulphoenix

yes - the switch is wired in full - but no 9v power running through it.

I checked/traced continuity from input jack to switch in to switch out to board. the same on output. checked my grounds. everything.

the circuit was working before the switch was wired....be jiggered if I know! and it works on bypass.

paulphoenix

it's a fuzz dog kit with his suggested true bypass switch wiring if that helps anyone?

I'd been right through the pcb and reflowed/removed and resoldered every joint prior to testing AOK with battery before moving on to the switch.

Sporky

I'd desolder lug 3 and check again - you may well be right that the switch is gone, but it pays to be methodical about these things, and you're going to have to desolder the switch if it is broken after all.

Was everything fixed into the enclosure when you tested without the switch?

paulphoenix

just thought that - i'll de solder lug 3 and 6 and measure with the DMM before resoldering and rechecking. if I get the same result would that indicate a pooped switch?

on my battery test the PCB and battery were not in the enclosure.

Sporky

I've had pedals go intermittent from tiny - in the visible-only-with-a-jeweller's-loupe sense - bits of swarf that I'd not cleaned out of the enclosure, so worth checking.

Might be the switch though.

Adam_MD

Also is it in the enclosure now? Very easy for the pedal to ground out if anythings touching the enclosure. This would stop it working while engaged but it would work on bypass.

ICBM

Could you have swapped the circuit input and output?

How is the switch wired? (ie what goes to each of the 9 pins.) The .3M reading could be the input or output impedance of the circuit depending on how it is.

paulphoenix

was hoping to put a picture up of my switch wiring but failed miserably.

it is a fuzzdog pedal parts kit and his switch wiring diagrams are on everyone of his kit build instruction PDF's.

Danny1969

Sounds like there's no bat neg connected to ground when you have the switch in circuit. Jump a wire from bat neg to ground of jack while switch is in position and see if it jumps to life

paulphoenix

just checked ground continuity all the way from DC socket (no battery in this 1590a enclosure) through the switch back to board ground and all ok. 

i'm going to desolder the suspected switch lugs (3&6) and check continuity later today. with nowt connected to the switch on these lugs i should get an OL reading. if i dont get OL then switch is bad i guess. 

thanks to all for your input and help.