Imagine a pedal gooped this way:

How do you trace a circuit from a stompbox you have? How to remove that ugly goop in your boutique stomper? All secrets are releaved here...
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R.G.
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Post by R.G. »

1. Use a 4 layer PCB, placing traces on the inner layers to connect points which should connect, and have about 20% of the outside layer traces look like they connect but really don't connect, to places that should not connect. Otherwise, make the outside traces easy to follow.
2. Leave some traces off entirely, putting only solder pads.
3. Solder loose loops of magnet wire to make the left-off traces connect properly.
4. Paint the circuit with a thin layer of epoxy. Let cure.
5. Paint the circuit with a thin layer of catalyzed urethane. Let cure.
6. Make a paste of epoxy and fine silicon carbide grit. Cover the circuit and embed the magnet wire connections in it. Let cure.
7. Make a paste of casting resin (polyester) and use pigment to color it some opaque color. Paint the circuit, lay small bits of metal or shavings on the curing polyester, then paint over them.
8. Using colored catalyzed epoxy, paint a smiley face on the top.

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okgb
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Post by okgb »

As imagined , either you would have something so great and original that you need to protect it, or
something so obvious and copiable that you need to hide it, didn't jack do a 4 layer board for his delay ?

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theblackman
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Post by theblackman »

and with these commandments 100 new boutique tubescreamers were born. so say we all.

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R.G.
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Post by R.G. »

I've been at this for far too long to worry about gooping.

But it is fun to imagine the looks on the faces of the folks trying to de-goop. And on those of the pedal builders trying to prevent de-gooping.

As we say here in God's Country, never a horse that couldn't be rode, never a rider that couldn't be throwed.

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Bill_Mountain
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Post by Bill_Mountain »

How much would it cost to fill the whole cavity with goop?

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R.G.
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Post by R.G. »

Bill_Mountain wrote:How much would it cost to fill the whole cavity with goop?
That's actually not a straightforward process. Most of the catalyzed goops are exothermic while curing, so they get HOT inside if you pour more than about 1/4". It's a recognized problem in potted military units. You can cook the components in extreme cases. In less severe cases, the heat causes thermal expansion, the goop cures good and hard, then cools. Those heat-expanded things cool and if they expanded too much and are not compliant enough, they can crack as they cool - not to mention that fragile solder joints could crack from the original expansion, then contraction.

There is a subsidiary problem in that the potting goo must conduct out 100% of the heat from the circuit. This is not all that big a problem for effects circuits, but could be in some situations. Could also be big enough to cause really bad thermal drift. Germanium doesn't need much temp change to go all drifty on you.

There's a highly specialized potting compound industry that serves these needs. The good stuff is expensive, and tends to be low-exothermic catalyzed urethanes that are not rigid when cured. They're more like tire rubber when cured.

The only circuit I personally ever potted was not an effect. Back in the .. er, 1970s I guess, I helped a friend with a sailboat install a battery monitor to keep up with the state of charge on his boat batteries. These were lead-acid marine batteries, and the state of charge is very nearly told by the voltage during discharge, with near 12V being full, and 10.9 or so being discharged enough to endanger the battery. We did an LM3914 in an expanded- and offset-scale setup to reflect the voltage in ten steps, with red-yellow-green LEDs showing charge. This circuit was all on one PCB, with the rectangle-faced LEDs protruding higher than the rest of the circuit. It was potted upside down with the LEDs' emitting faces at the bottom, stuck in a 0.1" thick layer of clear polyester. When this was semi-cured, the rest of the cavity up to the PCB was filled with opaque-white colored polyester; after a bit of solidification (and exotherm...) the rest of the back was poured, and the top covered with polyvinyl alcohol as an oxygen blocker to let the surface cure hard, not tacky. The mold was a machined cavity in HDPE, about 1.8 by 3 inches and maybe 5/8" deep, with rounded corners and about a 5 degree draft to de-mold. Mounting was by brass nuts set into the back of the unity by sticking them into the last layer. It was fun and I learned a lot about designing things that could actually be manufactured as opposed to hand-tinkered.

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digi2t
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Post by digi2t »

I still need to see my dentist, and ask him if he can x-ray this....

Image

Image

The stuff is hard as rock, and there's no way I'm going to start chipping away at this. It's the only Breg Sweep wah I've ever seen.

Then, there's the triple pot issue to deal with.

:hmmm:
No matter how many times I cut it, it`s STILL too short!

https://www.deadendfx.com/

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Jack Deville
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Post by Jack Deville »

okgb wrote:As imagined , either you would have something so great and original that you need to protect it, or
something so obvious and copiable that you need to hide it, didn't jack do a 4 layer board for his delay ?
I think the Mod zero was designed during a difficult period of my life in 2010?
I'm a "professional."
Buy my products and make me rich.

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mictester
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Post by mictester »

I've frequently gooped pedals - not to hide anything, but to provide protection. With some work, it's possible to completely waterproof a pedal. You'd be surprised how often a pedal on stage gets liquid over it - water, beer or worse.... I use waterproof push switches and where I have external controls, they're waterproof cermet pots. The waterproofing has enhanced the reliability of the pedals immensely!
"Why is it humming?" "Because it doesn't know the words!"

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Post by zoetrop »

I recently traced a Fulltone Secret Freq, and it has a multilayer pcb. Don't know if three or four layer, but top and bottom are both ground planes. Also, there was an additional gyrator which is covered in gray goo..: viewtopic.php?f=7&t=17993&start=20#p259343

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Post by fuzzbunny »

Seriously, it would be fun for both the designers and the degoopers.

I'd like to see some 'Pharoh's Tomb' board designs.

***********

Degooper: It was all going very well until the third layer....

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