I'm pretty new at pedal building having only built two pedals thus far. I'm in the middle of another build but this is the first one where I do not have board mounted pots. When I'm finishing it up and putting everything in to the enclosure should the board just be in there loosely or should it be connected somewhere? Also, do I need something in there to prevent a 'short' against the side of the enclosure?
Many thx!
As you've deduced, you need to prevent it from dancing all over the place because if something were to short out, that would be bad.
A popular solution are self-adhesive plastic standoffs such as these http://www.smallbearelec.com/servlet/Detail?no=76
Another option is just double sided tape (it's usually non conductive so you can just stick on the back without any problems)
Yet another solution is to make use of the little ridges inside the aluminium enclosures and make it so the PCB fits in there.
Or if all else fails, hot glue, but it doesn't really stick to the enclosure that well.
I find that the wiring usually keeps it from moving side to side to much. My boards are usually wide enough that there is not much movement anyway. As far as shorting on the backside of the board to the pots and so forth, I use a piece of corrugated cardboard wrapped in electrical tape, sized about the same or more than the board, and stick it underneath it. It's similar to like what commercial manufactures do like Boss. They stick a thick plastic sheet on the back of theirs between the board and the backplate.
Most well built electronics deal with anchoring the PCB to the box by using metal standoffs like here (http://www.smallbearelec.com/servlet/Detail?no=604). They allow the PCB to be removed for servicing easily, and are a very secure connection to the box that doesn't rely on solder connections for mechanical restraint. Actually, your effect will be more reliable having the pots on wires and the board secured otherwise.
For little PCBs, like effects, that are light weight, you may not need all 4 corners. Sometimes I'll use 2, catty corner, or even one for little daughter boards.
I have not used any adhesive standoffs yet, nor epoxied the metal ones. Occasionally I float it with all that wiring. I've been soldering a piece of stiff bus wire to anything- ground of a jack, unused contact on a switch. Then poke it thru pcb holes or perf holes, and bend it around. Very lazy, but they're holding up well. A little electrical tape here and there.
Not anchoring a PCB is very poor build paractice. Standoffs, screw/nut combos, etc are all better than leaving a PCB floating in the box. Leaving it unsecured is simply asking for issues.
A good source of insulation for under your PCBs is plastic jugs like a common gallon milk jug. Good insulation properties, easy to cut to shape, and thin. You can punch holes through the plastic that will fit over the pins of the self-adhesive stand offs, holding the insulation in place.
Quote from: Arcane Analog on October 08, 2014, 08:45:16 PM
Standoffs, screw/nut combos, etc are all better than leaving a PCB floating in the box.
I prefer to think of mine as "shock-mounted". :icon_wink: Like this beast: http://johnkvintageguitars.homestead.com/1970V4.html (http://johnkvintageguitars.homestead.com/1970V4.html)
Quote from: blackieNYC on October 09, 2014, 08:57:47 PM
Quote from: Arcane Analog on October 08, 2014, 08:45:16 PM
Standoffs, screw/nut combos, etc are all better than leaving a PCB floating in the box.
I prefer to think of mine as "shock-mounted". :icon_wink: Like this beast: http://johnkvintageguitars.homestead.com/1970V4.html (http://johnkvintageguitars.homestead.com/1970V4.html)
I am not sure how that amp in any way relates to floating a PCB. Floating a PCB is a pedal is simply an extremely poor build practice and it is only a matter of time before it causes problems. Nothing looks worse in a pedal than electrical tape.
Just making a devil's advocate-type of point. That ridiculously heavy amp is in a metal frame mounted with springs in a wooden box. Pretty nice idea for a tube amp. Or look under the hood if a live console- no card edge connectors, everything is ribbon cable, so the console can withstand a little twist here and there, in the back of the truck. Of course a pcb clattering around loose in a hammond box isn't a good idea- but there could be some downside to rigid mounting, at least theoretically. Epoxying standoffs looks a little dicey to me - haven't tried it yet. If they aren't perpendicular, or lined up perfectly with the pcb, or vary a little in height from the epoxy, I would think the board could end up with a little twist or torque on it, stressing traces or solder points, buss wire, etc. Easily half of audio repairs are broken solder joints at DC power jacks or audio jacks, where the chassis mounting and the solder mounting are at odds with each other. And if we do have pcb-mounted pots, we'd be wise to resolder the legs after tightening the pots to the enclosure. You'll feel the legs jump a little as the strain is removed. Commercial pedals now migh have 1/4" jacks soldered to it and also tightly screwed into the enclosure, even the stomp switch might be mounted this way. Looks like trouble.
When you use the self-stick stand offs or use some that you epoxy to the enclosure, you attach then to the board and them put the assembly in place. If you just leave it in place until the epoxy hardens the standoffs will be perfectly aligned. This is easiest to do after the board is populated, but before the off board wiring has been attached, but you can easily do it later as well. There should be no misalignment or torquing of the board.
The parts regarding the amp makes zero sense. The Ampeg PCB is bolted to the chassis through standoffs and the chassis is bolted to the cab. Only the leads are floating - as they should be. It has zero relevance to floating a PCB by wires. Any builder worth their salt does not float a PCB. Ever.
Edit: If you understand how to mount a PCB to the chasis there is nothing dicy about it.
Quote from: blackieNYC on October 10, 2014, 08:54:54 AM
Just making a devil's advocate-type of point. That ridiculously heavy amp is in a metal frame mounted with springs in a wooden box. Pretty nice idea for a tube amp. Or look under the hood if a live console- no card edge connectors, everything is ribbon cable, so the console can withstand a little twist here and there, in the back of the truck. Of course a pcb clattering around loose in a hammond box isn't a good idea- but there could be some downside to rigid mounting, at least theoretically. Epoxying standoffs looks a little dicey to me - haven't tried it yet. If they aren't perpendicular, or lined up perfectly with the pcb, or vary a little in height from the epoxy, I would think the board could end up with a little twist or torque on it, stressing traces or solder points, buss wire, etc. Easily half of audio repairs are broken solder joints at DC power jacks or audio jacks, where the chassis mounting and the solder mounting are at odds with each other. And if we do have pcb-mounted pots, we'd be wise to resolder the legs after tightening the pots to the enclosure. You'll feel the legs jump a little as the strain is removed. Commercial pedals now migh have 1/4" jacks soldered to it and also tightly screwed into the enclosure, even the stomp switch might be mounted this way. Looks like trouble.
Quote from: blackieNYC on October 10, 2014, 08:54:54 AM
Easily half of audio repairs are broken solder joints at DC power jacks or audio jacks, where the chassis mounting and the solder mounting are at odds with each other. And if we do have pcb-mounted pots, we'd be wise to resolder the legs after tightening the pots to the enclosure. You'll feel the legs jump a little as the strain is removed. Commercial pedals now migh have 1/4" jacks soldered to it and also tightly screwed into the enclosure, even the stomp switch might be mounted this way. Looks like trouble.
Anything that is mounted with hardware fixings and PCB solder joints should not be soldered until all of the hardware has been tightened to final torque, e.g. jacks, pots, TO-3/TO-220/TO-126 case outlines.
It's surprising how much damage a drop from table height will cause, but consistent vibration is a lot worse. Quite often I used to see broken power transistors in the bottom of pinball machines, usually when the last repairer couldn't be bothered screwing them down after replacement.
david