DIY A/B Switch Dasy-Chain problem

[Carry.White]

Hi everybody,

as my first project I made myself a simple A/B-Switch. For this build I used this circuit:


The switch works as expected, but when I put it into a dasy chain like this one,

together with other guitar pedals, the whole chain loses power. When I connect the A/B-Switch, every pedal in the chain turns off, including the A/B-Switch. When I disconnect the A/B-Switch, the chain powers up and the other guitar pedals turn on again. When I disconnect all the other guitar pedals and when I leave only the AB-Switch in the chain, the switch works fine.

So now I ask myself ...


Do you have an idea, why this is happening and ... (maybe) how to fix it.
Any suggestion would be greatly appreciated.

Matthias

[duck_arse]

hello and welcome, Carry.White.

more information, please. did you use a metal DC socket? this will usually short the supply to ground via the metal box, due to the way the jack is constructed. do you have anything plugged into A or B? or In, even? did you make any wiring errors, and can you prove/disprove by showing us photos of what you have built?

do you own a multi-meter?

[Carry.White]

Hi duck_arse  ,

thank you for your answer. Yes, I did use a metal DC socket. With this post I provide some pictures of the box I built.





I just double checked all the wiring and it seems okay to me. I just discovered, that all the pedals in the chain stay powered, when nothing is connected to my A/B-Switch. When I connect either one of the output ports, everything stays powered, too. But as soon as I connect the input port, the power goes away. When I disconnect the input port from the metal chasis, the chain stays powered, too.

What is your advice? Should I just, isolate the input jack from the chasis? I do own a multimeter ...

Matthias

[duck_arse]

well, the outer connection of the DC jax is usually the positive, because it is easier to switch-out an internal battery thus configured. and - the outer connection of all your metal-flanged audio jax is usually - no, ALWAYS - ground. so when you connect a DC jack with a metal body to a metal box with grounded jacks, you short the V+ and the ground together. you can test this with your meter, on continuity or ohms setting (no circuit power for resistance measures .....) and it should show 0R, or beep.

if you can isolate the DC jack from the metal box, it should be ok [otherwise, use a plastic bodied dc jack], but you should test all the connections with the meter before you power on, to ensure you haven't grounded a signal or cross wired supply. it only takes a few minutes, and can save a lot of trouble.