Boost pedal shorts... everything.

JankJetsun · May 04, 2021, 05:32:23 PM

Howdy everyone,

So I built a JHS Mini Bomb boost with instructions from the effectslayouts blog and when daisy chained with my OneSpot it shorts out pretty much any pedal it's connected to.
It works fine on its own, I don't think I deviated from effectslayouts' layout and general layout. I can plug two pedals into the power and they're fine. But if I connect the patch cables it shuts off anything it's connected to.

Any thoughts?

stallik · May 05, 2021, 02:05:21 AM

Is it negative or positive ground?

bluebunny · May 05, 2021, 03:27:15 AM

Looks like it's a simple J201 JFET boost, so negative ground. Here's the layout, fyi:

http://effectslayouts.blogspot.com/2015/10/jhs-minibomb.html

ElectricDruid · May 05, 2021, 05:39:02 AM

It sounds like the off board wiring must be wrong. Perhaps the wrong supply wire taken to the jack ground?

Can we see a picture of your build please?

JankJetsun · May 05, 2021, 10:36:33 AM

Wellp. I rebuild the whole board as I didn't have some tools when I did the first. I thought I did a much cleaner job but now she gets no sound at all. Though I figure I should redo that sloppy wiring next. Everything's still a bit long while I'm testing.

Here's pictures.

duck_arse · May 05, 2021, 10:55:09 AM

what - no welcome, fellas?

welcome to the forum, JankJetsun. it seems you have a metal bodied DC jack, which will cause problems when wired correctly. using a standard power supply, the cable connector will be negative centre, positive barrel. from your wire colours on the DC in jack, I'd guess you have wired it backwards. but when you have the barrel wired positve with a metal jack, it will short the supply to ground via all your patch cables, so we either isolate the jack from the case, or use a plastic.

JankJetsun · May 05, 2021, 11:15:18 AM

Thanks for the welcome!
I read about that one earlier and stuck a rubber grommet on the DC jack so it would be isolated. Is that not enough?

My wire color is all over the place. The red is the 9v, black is the ground.

On the input jack blue is ground from the switch, black is the ground from the board, white is the switch.

Kevin Mitchell · May 05, 2021, 11:39:55 AM

I suggest you wire it from scratch.

You wired the power to only ground the pedal when off/bypassed. So when the pedal is on you're losing ground connection for the entire pedal which probably wasn't an issue before the grommet. I also see that your input jack is relying on chassis ground as there's nothing on the sleeve lug. Also the tip of the input may be shorting with one of the potentiometer lugs when you plug in the instrument cable but I think that connection is suppose to be made anyways on the board - so it wouldn't be an issue.

Edit again:
Look up a diagram for true bypass wiring. Keep in mind that if you're not using a status LED you wouldn't have to wire one of the switch poles so a whole column would be disconnected in that situation. The ground to the stomp switch is only for a status LED.

These issues are simple enough to resolve. I find it best to gut it and learn from the mistakes.
And welcome to the forum.

Marcos - Munky · May 05, 2021, 11:52:36 AM

First of all, welcome!

Even you insulated your metallic dc jack from the enclosure, you still have the red wire connected to the center. A pedal power supply have negative center, so your dc jack wires are reversed.

Kevin Mitchell · May 05, 2021, 11:55:52 AM

Quote from: Marcos - Munky on May 05, 2021, 11:52:36 AM
First of all, welcome!

Even you insulated your metallic dc jack from the enclosure, you still have the red wire connected to the center. A pedal power supply have negative center, so your dc jack wires are reversed.

Good catch!

Without the onespot, they must be using a reversed battery or a center positive power supply if it were truly functioning.
That also means the pedal was fed reverse voltage which is a recipe for disaster. Especially with no power protection. Luckly the parts in this pedal are a bit more forgiving than a pedal built with ICs.

JankJetsun · May 05, 2021, 12:08:23 PM

Quote from: Kevin Mitchell on May 05, 2021, 11:55:52 AM
Quote from: Marcos - Munky on May 05, 2021, 11:52:36 AM
First of all, welcome!

Even you insulated your metallic dc jack from the enclosure, you still have the red wire connected to the center. A pedal power supply have negative center, so your dc jack wires are reversed.
Good catch!

Without the onespot, they must be using a reversed battery or a center positive power supply if it were truly functioning.
That also means the pedal was fed reverse voltage which is a recipe for disaster. Especially with no power protection. Luckly the parts in this pedal are a bit more forgiving than a pedal built with ICs.

I'm only using the OneSpot. It was working as far as the pot was adjusting volume and footswitch was working when not plugged in to other pedals. I'll find a different diagram and take a shot at rewiring it. The initial instructions I used were are this: https://effectslayouts.blogspot.com/p/general-layout-notes.html

Kevin Mitchell · May 05, 2021, 01:06:18 PM

Quote from: JankJetsun on May 05, 2021, 12:08:23 PM
I'm only using the OneSpot. It was working as far as the pot was adjusting volume and footswitch was working when not plugged in to other pedals. I'll find a different diagram and take a shot at rewiring it. The initial instructions I used were are this: https://effectslayouts.blogspot.com/p/general-layout-notes.html

Better off wiring ground to the input. Not sure why they left it out. I mean it'll work but we like a clean ground connection. If you were using a nonconductive enclosure like a plastic box you'd have a floating ground connection on the input jack. That's no bueno.
The diagram is also grounding the input of the board when in bypass mode. That isn't necessary since the board is not connected to the jacks in bypass mode anyways. Maybe someone can explain why it's drawn like that. I don't understand the reason myself. If I were to guess I'd say to decrease crosstalk within the bypass switch? But I've never worried about that. With high gain or boost circuits perhaps it's something to consider.

Notice that the DC jack ground goes to the circuit board first. It's routed through the board acting as a wire. So ground is always connected to the board, jack and switch. But again, the switch should only have ground for a status LED (minus my previous observation on grounding the board's input in bypass mode). So you'd want to wire it as if it were a DPDT switch leaving one pole/column totally unsoldered - being the center pole of the switch in the drawing unless you decide to add an LED and/or ground the board's input when bypassed.

JankJetsun · May 05, 2021, 02:05:56 PM

So I think I got to the same things you're talking about here. But no dice. Now the ground goes to the input where it's linked to the output ground, and DC center pin. Still getting no dice though. I've built three boards as well and not getting anything out of them. Been testing from the switch and pot into the board with the multimeter and everything seems fine. Also tested that the pot was good. Kind of feels like I'm hitting the wall for what could be wrong.

One thing I've noticed is only that first board makes line noise when I handle it.

Kevin Mitchell · May 05, 2021, 02:19:07 PM

Are the tips of the mono jacks hitting the enclosure when you plug in the instrument cables? That would ground the signals.

Wiring is looking better by the way!

JankJetsun · May 05, 2021, 02:22:55 PM

Nope. But I think I might have a culprit. The board in the 1m pot is shaky. It was giving sound when I pulled on the wires. I tried resoldering them but it just cut out. But when I shake it it pops pretty good. Problem is I don't have any more 1m's. Plenty of various others though. Would a pot of a different value do alright in there?

Kevin Mitchell · May 05, 2021, 02:48:43 PM

Quote from: JankJetsun on May 05, 2021, 02:22:55 PM
Nope. But I think I might have a culprit. The board in the 1m pot is shaky. It was giving sound when I pulled on the wires. I tried resoldering them but it just cut out. But when I shake it it pops pretty good. Problem is I don't have any more 1m's. Plenty of various others though. Would a pot of a different value do alright in there?

1M would give more resistance away from ground for a louder boosted signal. So you may get less volume with a lower value pot. So less resistance = less adjustable range.

A lot of pot shafts move. You could just be pulling the wipers from the carbon track of the wafer. Doesn't mean it's broken, just that isn't as sturdy of a pot and may be further compromised one day from typical (or not typical) use.
Pulling on the pot shaft is like plugging the output cable in and out.

I think the main issue is confusion with the power supply & jack still. Verify what's what and make sure the board connections are correct. I know you're trying. Keep at it

garcho · May 05, 2021, 02:54:44 PM

Use the highest value pot you have and order some more 1M. This will only be one in a long line of pedals you don't even know you're going to make yet...

Any chance you have the diode the wrong way around? Is it still shorting out other pedals?

QuoteI've built three boards as well and not getting anything out of them.

Take pictures of them, both sides, including the component side. This is a very simple circuit, you're gonna figure it out, don't give up.

JankJetsun · May 05, 2021, 03:09:30 PM

Quote from: garcho on May 05, 2021, 02:54:44 PM
This is a very simple circuit, you're gonna figure it out, don't give up.

Oh, I'm not gonna. A bit frustrated. But I'm gonna beat my head against the wall till I figure it out

Then I'm gonna sit down and read a whole lot more about how this works. I'm sure I've made a really simple mistake somewhere.

Here's the first semi-working monstrosity I made and the third cleaner board. I've misplaced the second one somehow.
The first actually gets sound when I put my finger across the pins of the 500k pot I did to test. Gonna swap back in the other.

Edit: And it does power fine with other pedals now.

And I really appreciate all the help!

garcho · May 05, 2021, 03:45:21 PM

QuoteThe first actually gets sound when I put my finger across the pins of the 500k pot I did to test

Here's the schematic of the circuit JHS used to make their pedal, from Tim Escobedo:

That pot is where all of the sound going to the circuit comes from. Your guitar's input has to get through that thing before any of the fun stuff can happen, so that's a pretty big clue. I can't really tell from the pics you put up, looks fairly clean to me. Could it be the lug on the pot that should be at 0V isn't connected to ground?

JankJetsun · May 06, 2021, 11:40:09 AM

Alright. Found out my 1m pot died. I swapped in a 500k pot and got the first one "working" but the volume is about the same as the unboosted volume. As I understand it I need to change a resistor or add a trimmer pot to adjust that. I don't have a trimmer nor socketed the resistor so I'm gonna file this under "failed but learned something". Order the stuff to do this over following the Duende and do this again after I tackle another project or two.

Thanks for all your help, guys.

News:

Boost pedal shorts... everything.