diy pedal board power supply question

[jnTracks]

Let me say, I really, really appreciate all the help and all the questions, noisy or not, in the service of trying to help me!

OK amp and board supply are both grounded, 3 prong.
In the supply I put ground wire to chassis, AC hot and neutral to the 120v transformer winding of all three transformers. The schemo here https://www.generalguitargadgets.com/pdf/ggg_ps_rps_sc.pdf
Is what I did, three of these in one box. (With different transformers and voltage regulators for each desired voltage). The grounds for each rail are common but separate from each other, and floating (not grounded to chassis) just as shown in the schemo.
I did wire all the output jacks for negative tip since it is more common, and to prevent confusion while building it, knowing I had a polarity reverse power cable that is a different color. So when my pedal board is populated it will be clear which power cable is reversed (different color) so I won't mix it up. I did test with DMM and confirmed that they all output negative tip, and the polarity reverse cable makes it positive tip. So polarity is reversed only once.
The noise only appears when the 12v is connected to the pedal. The 9v pedals and 18v pedals connect, power up, and operate fine from this supply.

 

[abbey road d enfer]

The grounds for each rail are common but separate from each other, and floating (not grounded to chassis) just as shown in the schemo.

  Do you mean the three 0V are tied together and go to all the sockets? This is not what I call floating... This may well be the cause of your problem, because all your 0V are tied together, and then you connect the 12V to ground (via the pedal), so that's actually a short circuit for the 12V supply.

 

[jnTracks]

The grounds for each rail are common but separate from each other, and floating (not grounded to chassis) just as shown in the schemo.

  Do you mean the three 0V are tied together and go to all the sockets? This is not what I call floating... This may well be the cause of your problem, because all your 0V are tied together, and then you connect the 12V to ground (via the pedal), so that's actually a short circuit for the 12V supply.

No no, I put three copper wires, one for each rail of the supply, they don't connect to chassis ground or to each other. They are the connection for each of the ground symbols in the schemo. Does that make sense?

 

[jnTracks]

Wait, that gave me an idea:

I don't have the supply in front of me right now but... The power jacks I used for the outputs have 3 pins (so the can be used to switch battery on/off when the plug is connected) but I didn't use the switch pin in this design.
I'm feeling a little scramble-brained with out looking at a diagram of the power jack but could the polarity reverse cable I'm using mean that the switch pin feature is causing the short or ground loop or something?

EDIT: actually that doesn't makes sense because the power cable tests at +12v on the tip when connected... I'm going crazy.

 

[abbey road d enfer]

EDIT: actually that doesn't makes sense because the power cable tests at +12v on the tip when connected... I'm going crazy.

How do you measure that? on the plug?











,

 

[jnTracks]

Yup.
Plug the reverse polarity cable into the supply. Red probe in the center of the barrel connector, black probe on the shell.

 

[abbey road d enfer]

Yup.
Plug the reverse polarity cable into the supply. Red probe in the center of the barrel connector, black probe on the shell.

Ok, that doesn't prove anything really, but now I can aasure you that the 12V PSU should be completely disconnected from the others.
Look at the attached schemo. See how the -12V pole is connected to the ground? Now if you already have a connection between all the PSU's it's going to conflict.

 

[jnTracks]

The transformers black wires (120v winding) are fed from one AC input (IEC connector to the wall outlet)
Besides that, there are absolutely no connections between the supplys.
I think I see what you're saying about -12v poll to ground but if the pedal takes 12v center positive then the center in the pedal isn't connected to ground, isn't it connected to hot in the pedal?
Also you have ground in the audio path connected to ground in the power path. Aren't those separate? I don't have DC in my guitar cables, do I?

 

[abbey road d enfer]

The transformers black wires (120v winding) are fed from one AC input (IEC connector to the wall outlet)
Besides that, there are absolutely no connections between the supplys.

In a precedent post, you wrote: "The grounds for each rail are common but separate from each other" . What does it mean?

I think I see what you're saying about -12v poll to ground but if the pedal takes 12v center positive then the center in the pedal isn't connected to ground, isn't it connected to hot in the pedal?

You must assume anything in this respect. There is no standard. I've seen both types. I had a wireless receiver that couldn't share a PSU with any other pedal.

Also you have ground in the audio path connected to ground in the power path. Aren't those separate?

How could they be separate? One of the PSU poles must be connected to the audio reference (usually ground).

I don't have DC in my guitar cables, do I?

It happens...

 

[jnTracks]

As you can tell I've not been doing DIY for more than, maybe a year, so I'm sure my terminology will be off sometimes.
By "grounds are common but isolated" I meant common with in each section of the PSU. So each transformer connects to a bridge rectifier and then the negative on the rectifier, cap1, regulator, cap2, output jack are connected. As in the schemo I linked to.
But that ground connects to nothing else.

Soooo, this might be something I can't just flip the polarity of the power cable.
Maybe it wants to see 12v "below" ground? Would that happen if I reversed the components in the PSU circuit? If I swap the + - on the rectifier and regulator would I have inverted voltage? The caps are electrolytic, and ummmm... Those should, or should not, be reversed as well? (Assuming this is even the right thing to do)

I'm sending an email to effectrode about running his pedal from a tip negative PSU with polarity reversed cable. Hopefully he will be able to tell me something helpful.

What an adventure this has become.

 

[abbey road d enfer]

As you can tell I've not been doing DIY for more than, maybe a year, so I'm sure my terminology will be off sometimes.
By "grounds are common but isolated" I meant common with in each section of the PSU. So each transformer connects to a bridge rectifier and then the negative on the rectifier, cap1, regulator, cap2, output jack are connected. As in the schemo I linked to.
But that ground connects to nothing else.

OK, so they are floating.

Soooo, this might be something I can't just flip the polarity of the power cable.

You can actually. You can do it at the socket or using a reverse cable.

Maybe it wants to see 12v "below" ground? Would that happen if I reversed the components in the PSU circuit? If I swap the + - on the rectifier and regulator would I have inverted voltage? The caps are electrolytic, and ummmm... Those should, or should not, be reversed as well? (Assuming this is even the right thing to do)

Don't do that, the regulators cannot be reversed.

I'm sending an email to effectrode about running his pedal from a tip negative PSU with polarity reversed cable. Hopefully he will be able to tell me something helpful.

The only question is which pin of the socket goes to the unit's ground.

 

[jnTracks]

That all makes sense

I await what the effectrode guy has to say

Thanks for sticking with me on this!