Tayda Tone Bender PNP with 3PDT PCB

[makisushi]

Ah!
Another week, another (failed) pedal! I was on a good streak with my last builds, and I thought this one would be easy, but oh! Was I wrong?


So I built the Tayda Tone Bender PNP version (with 2N3906 for now), BUT I also used this 3PDT breakout PCB from pcbway, which works great on my other pedals. Now, I don't think I fully understand this whole 9v+ and 9v- thing because the first time I plugged the pedal in with a wall adapter: POW! Blew a cap… Replaced the cap, used a 9v battery, and this is where it gets complicated:

1. The 9v battery is wired the right way on the 5.5mm x 2.1mm DC male adapter, which means the center is POSITIVE and the outer is NEGATIVE.
2. On the pedal, the center pin is "NEGATIVE" (black wire), and the outer is "POSITIVE" (red wire). So right there, the polarity is reversed, but
3. The pedal does work like that.
4. However, the LED doesn’t work on 3PDT breakout, and I get a reversed voltage reading with V- on the positive lead and GND on the COM lead.
5. So where exactly is the ground going? Why is just not named the other way around? Do I just flip the LED on the breakout PCB, or does that mean that all my “ground” (black wire) from the 3PDT PCB is actually feeding the hot signal? Since I don’t want to blow more caps, how do I fix this the right way, the first time?

 

[makisushi]

So I did reverse the polarity of the battery AND the polarity from the breakout to the fuzz.

AND NOW:
I will name it the "Skrillex Fuzzstep"

 

[BrainDrain]

For positive ground circuits the LED will be reversed. Long leg to “positive ground” (red) and short leg to “negative 9v” (black)

With “positive ground” circuits you’re just reversing the positive and negative going into the pedal. I can’t tell from the pics if this pcb is specifically laid out for positive ground but usually it requires reversing any polarized components too. So for example, electrolytic capacitors will be reversed.

The easiest way for me to think about is just reversing the red and black wires that connect to the pcb and making sure any polarized components are reversed. Black wire to 9v and red wire to ground. And now using the red wire’s path for anything that needs to be grounded. Like the LED which will be grounded on the positive side now (long leg).

 

[makisushi]

thank you, that's basically what I did after, but now there's something else wrong, as you can hear from the video. It did not sound like that with the breakout PCB "Wire the wrong way". On the circuit PCB, it says -9V and ground, but now it’s wired in a way where the ground gets 9V, and the -9V is actually ground. I don’t really understand why they don’t just label things the right way, which makes me think there’s a reason for it that I don’t yet understand.

The problem is I’m using a 3DPT breakout which wasn’t designed for reverse polarity. So, the ground on the breakout is actually ground, but the ground is -9V on the circuit PCB. I don’t know if that makes sense, but anyway, I’ve put the project on hold. I ordered a charge pump to put between the breakout PCB and the circuit PCB. That way, all the grounds should be correct, and hopefully, everything should work fine.

 

[BrainDrain]

The way you have it wired now sounds correct. Red wire to ground and black to -9v. Just make sure if you wire it to a power jack that the black -9v is wired to the center pin of the jack so its center negative.

Also, you don’t need a charge pump unless you plan on daisy chaining it with other pedals. The 3PDT pcb has no effect on the circuit being negative or positive ground. It’ll work with either one. It’s just routing whatever you put into it. You just use anything labeled “ground” for the red wire and anything labeled “-9v” (or 9v) for the black wire now. And also reverse the LED.

The pcb is just labeled it that way to let you know it’s positive ground but you can also wire it as negative ground if you wanted to by just reversing the red and black wires again (black to ground, red to -9v) and reversing everything that’s polarized while also using NPN transistors.

I know it’s somewhat hard to grasp (it still confuses me a bit even with a basic understanding) but it’s called “positive ground” because the red ground wire being at 0 volts is now “more positive” than the black being at -9v. Zero is more than negative nine. If I have zero dollars I’m dead even but if I have -9 dollars I owe someone money.

 

[makisushi]

thank you for your explanation. I made a quick drawing but I'm pretty sure at the point that we both say the same thing. I found out that I was using a bad flux (i thought i got rid of them) which might be the cause of the new problem. I had problems with others build that were solved by soaking the board in 99% alcool, "tooth brush it" and reflow the parts. It's a flux used to solder 18650 batteries and I think it cause a lot of issues with PCB. It's vey sticky and greasy at the same time... I'll let you know

 

[BrainDrain]

Also if you have the power jack wired for “center negative” (-9v to center and positive ground to outer) you want to keep the battery wires as normal on the adapter or else you’ll be feeding positive voltage into the center of the jack. (Most likely what happened the first time)

 

[BrainDrain]

thank you for your explanation. I made a quick drawing but I'm pretty sure at the point that we both say the same thing. I found out that I was using a bad flux (i thought i got rid of them) which might be the cause of the new problem. I had problems with others build that were solved by soaking the board in 99% alcool, "tooth brush it" and reflow the parts. It's a flux used to solder 18650 batteries and I think it cause a lot of issues with PCB. It's vey sticky and greasy at the same time... I'll let you know

Yeah that wiring won’t work because the 3PDT was labeled for negative ground. Let me see if I can adjust it for you.

 

[BrainDrain]

Swap each of these sets of wires only on the 3PDT board.

 

[makisushi]

yes but what I did is wire the 3PDT breakout the "normal negative center pin" but reverse the polarity at the PCB . I don't use battery. If I do what you ask, won't the jack's grounds be instead the hot signal? I think I'll just use a regular 3PDT with the charge pump in the pedal. The breakout seems to cause a lot of issues with positive ground.

 

[BrainDrain]

What you’re doing won’t work. All the breakout board is doing is routing the power into the pedal, but if you put the wrong order in you’ll get the wrong order out. The pcb isn’t getting -9v and ground the way it needs. The grounds are now “positive ground”, so yes, the input and output jacks ground lugs will be connected to the “positive ground.” It’s still ground, it’s just positive. The charge pump is doing exactly the same thing as reversing the wires but keeping the power the same up front so you can daisy chain it with other negative ground pedals. If you plan on daisy chaining it then definitely do the charge pump. If you’re gonna use a battery or it’s own dedicated power supply it’s kind of a waste. Wire it up as shown in the picture I posted and it will work. Connect everything else the same. I’ve built quite a few positive ground pedals so I’ve been through all of this before. Don’t worry.

 

[makisushi]

thank's I'll give it a shot and let you know