Power Issues with two pedals in one enclosure

[dobo2001]

I'm currently working on a dual pedal project, with a PedalPCB Abyss (EQD The Depths) and a Aion Vector (Mad Professor Deep Blue Delay), and I can't get the power wiring correct. I've tested the source with a multimeter and it's working fine at 9V, but if I test the leads on the jack itself, I only get ~1.4V.

I think this has something to do with the ground wiring, as if I leave off any ground wires I get 9V from the jack leads, but obviously the pedal doesn't work without those grounds. I currently have it wired with

* 2 wires from the +9V of the jack to the two pedals' respective +9V spots

* 1 wire from the Ground of the jack to the ground of the input jack

* 1 wire from the Ground of the jack to the ground of the Abyss board

For the circuit grounds I followed the diagrams provided for both of the PCB's (pretty much everything to the sleeve of the input jack), the only thing I changed was wiring the output of the Abyss to the input of the Vector. Any help is appreciated!

[antonis]

Wellcome dobo...!!! 

It seems to me like you've mixed up 2 reverse polarity protection power diodes (each one for individual circuit) in the wrong direction, but without a schematic of your circuit it's hard to say..

[dobo2001]

After some more testing, everything works perfectly until I connect a ground from the Abyss PCB to any ground spot within the enclosure. The Aion Vector works fine, but as soon as I solder on a ground for the Abyss the voltage drops from 9V to ~1.5V. Here's a link to the schematic and wiring diagram: http://www.pedalpcb.com/docs/Abyss.pdf. Obviously the Abyss doesn't work without a ground, any tips on how to get it from dropping the voltage?

I also have not installed any protection diodes unless they are already included on the PCB's. I am wondering if not socketing the MPSA18 transistors could be causing problems, could they have possibly been heat damaged?

[bluebunny]

Does the Abyss work on its own?

[amptramp]

I tend to suspect electrolytic bypass capacitors when this happens.  When they short, they may have enough resistance to allow some voltage to ground.

[dobo2001]

Does the Abyss work on its own?

No, as when there is a ground connection, there isn't enough voltage, and when there isn't a ground connection, it doesn't work.

[dobo2001]

I tend to suspect electrolytic bypass capacitors when this happens.  When they short, they may have enough resistance to allow some voltage to ground.

There are two 47uF caps right before and after the intensity pot, could these be shorting?

[Slowpoke101]

You seem to have a short circuit or near short circuit with your Abyss board.
Hopefully you used IC sockets for the ICs. Remove the ICs and reconnect power.
If you now have full 9 Volts one of the ICs may be toast or was installed with the incorrect orientation.

If you can upload some pictures of your board (component side and solder side) it would be very helpful.

[amptramp]

I tend to suspect electrolytic bypass capacitors when this happens.  When they short, they may have enough resistance to allow some voltage to ground.

There are two 47uF caps right before and after the intensity pot, could these be shorting?

I don't think that would cause the problem you are seeing.  The 100 µF cap on the power supply input could be the culprit.

[dobo2001]

You seem to have a short circuit or near short circuit with your Abyss board.
Hopefully you used IC sockets for the ICs. Remove the ICs and reconnect power.
If you now have full 9 Volts one of the ICs may be toast or was installed with the incorrect orientation.

If you can upload some pictures of your board (component side and solder side) it would be very helpful.

Just did that, looks like the TL074 was installed backwards  . Flipped it around and voltages are working correctly and the pedal is working. Thanks!

[bluebunny]

Just did that, looks like the TL074 was installed backwards 

Your secret is safe.  I don't think anyone read that.   

It's a worthwhile habit - until you've got a few of these under your belt - to power-up initially without ICs in place and to measure their respective power pins on the sockets.

[antonis]

It's a worthwhile habit - until you've got a few of these under your belt - to power-up initially without ICs in place and to measure their respective power pins on the sockets.

And don't forget to place them in sockets shortly afterwards..