PCB Mounting?

[Steve Mavronis]

What is common practice for mounting PCB inside the pedal case? Some commercial pedals have pots that come with angled lug standoffs that are soldered to the PCB suspending it. They seem to be hard to find and I'm not sure of the distance (0.6"?) from the center of the knob to the solder pads anyway. I've seen others use the 3PDT pins soldered to the PCB. Or do you use some other type of standoffs to secure the PCB or wrap it in a cardboard sleeve? Also, do you prefer the component side showing (facing the bottom) when you open the case? What do you DIY'ers do?

[audioguy]

Devi Ever wraps her commercially sold circuits in f'n electrical tape.

I use http://www.smallbearelec.com/Detail.bok?no=76

[StereoKills]

^ +1 for the standoffs. Very solid and make it easy to remove the board to do repairs, mods, etc without destroying anything.

[alparent]

I really like moosapotamus way of doing it.

http://moosapotamus.net/IDEAS/ADAflanger/ADA_MN3007/ADAflanger_MN3007.html

Do know what he uses to glue the bolts to the enclosure ? epoxy? J-B weld?


I also like to use 3M heavy duty double sided tape on small boards.

[Steve Mavronis]

^ +1 for the standoffs. Very solid and make it easy to remove the board to do repairs, mods, etc without destroying anything.

I guess you could have "loose" standoffs, fitting the internal box height that goes through board corners where you can adjust how high it's suspended?

[G. Hoffman]

From a reliability point of view, there are no adhesives that really work all that well on metal.  Because of this, my preference is to use countersunk #4 stainless steel screws with aluminum standoffs.  It's not the best looking thing, but it is strong as can be, and the chance of having problems, even in the roughest touring situation, is pretty small.  I also use lock nuts to bolt everything down, so I don't have to go in and tighten anything. 

Mind you, I'm a sometimes stage hand, so my opinion of reliable is something that can survive an 18 month world tour, being tossed around by a bunch of I.A.T.S.E goons without ever once needing any repair work.  It is probably an impossible standard, but it is my goal. 


Gabriel

[Taylor]

I use board-mounted pots. Solves the problem of mounting the PCB, makes building much easier and quicker and also quieter because there aren't wires connecting everything.

[Processaurus]

From a reliability point of view, there are no adhesives that really work all that well on metal.  Because of this, my preference is to use countersunk #4 stainless steel screws with aluminum standoffs.  It's not the best looking thing, but it is strong as can be, and the chance of having problems, even in the roughest touring situation, is pretty small.  I also use lock nuts to bolt everything down, so I don't have to go in and tighten anything. 

Mind you, I'm a sometimes stage hand, so my opinion of reliable is something that can survive an 18 month world tour, being tossed around by a bunch of I.A.T.S.E goons without ever once needing any repair work.  It is probably an impossible standard, but it is my goal. 


Gabriel

That way is really the most professional (not necessarily commercial!), and reliable.  That's a pedal that can get thrown at a wall.  The couple times I've been convinced to do a commission for someone, I'm glad I took the time to do it like that, so that the odds of it flaking out at a bad moment (like on the old world tour) are slimmer.

PCB mount pots are crucial for production, but suspending a board with a measure of weight solely by soldered electrical connections is an inferior mounting technique.  Mil spec specifies any external user controls be wired, not PC mount.  I love PC mount pots since small bear started carrying them too,  but it isn't as bulletproof as mechanically secured standoffs.   I could see pseudo PC mounting pots on bare wires that could have a bend in them, to act as a shock absorber, while still making assembly straightforward.  Then the board could be standoff'ed.

[soggybag]

For a small board you can always use some foam double sided tape and stick it to the inside of the box or the back of the pots.

[Steve Mavronis]

I love PC mount pots since small bear started carrying them too,   but it isn't as bulletproof as mechanically secured standoffs.

Are the Alpha 16mm PC angled mount pots at Small Bear called Reverse Audio the same as Reverse Log as used in some pedal gain controls? Can you give me the distance from the center of the pot to the PCB mounting right angle point so I can know where to place the pads relative to the knob positions, and are the 3 mount points 1/10" apart? I can't find a data sheet for the physical specs. Maybe I can use them in conjuction with standoff spacer screws for added support.

[Taylor]

Here's the data sheet for those pots.

http://www.taiwanalpha.com/english/p_e_27-6.htm

[Steve Mavronis]

Thanks! So it looks like they are 0.63" from the pot center to PCB holes which are 0.2" apart.

[G. Hoffman]

...snip

Mind you, I'm a sometimes stage hand, so my opinion of reliable is something that can survive an 18 month world tour, being tossed around by a bunch of I.A.T.S.E goons without ever once needing any repair work.  It is probably an impossible standard, but it is my goal. 

That way is really the most professional (not necessarily commercial!), and reliable.  That's a pedal that can get thrown at a wall.  The couple times I've been convinced to do a commission for someone, I'm glad I took the time to do it like that, so that the odds of it flaking out at a bad moment (like on the old world tour) are slimmer.

...snip

I have a friend who was the keyboard tech for NIN durring the Downward Spiral tour.  Basically, he had to completely rebuild all of their on-stage keyboards every day (they were WAY striped down - nothing more than keyboards, really, with no program change or sound in the actual keyboard - all of that was off-stage), because Trent liked the way those old DX-7s spray when hit with a Les Paul.  So, what I really want is to make a box that could survive an entire NIN tour, but I KNOW that is impossible.  I'm sure that at some point, Trent would decide it was his mission to @#$% it up!

But yeah, putting weight of any sort on a solder joint is just asking for trouble.  And while I've kind of been enjoying making surface mount circuit boards recently (no drilling!  YEAH!), they are also a bad idea for durability.  My shop probably bills Taylor Guitars into 5 figures a year to replace the silly surface mount parts on their earlier ES system electronics (the new ones have DIP ICs and electrolytics, but they are still using a lot of surface mount resistors and caps - still, a LOT better).  Solder joints simply are not a structural connection.


Gabriel

[mth5044]

Devi Ever wraps her commercially sold circuits in f'n electrical tape.

I use http://www.smallbearelec.com/Detail.bok?no=76

I used to wrap them in electrical tape too 

Do you know the size of the hole needed for those mounting standoffs?

[StereoKills]

I use .159" holes. A nice snug fit.

[devi ever]

Yeah, I've been wrapping my circuits in electrical tape for nearly a decade (having hand built thousands using that lo-fi technique) and NEVER, I repeat NEVER had a pedal returned with any issues because of that.  (it's not like they're free floating.  They are gently hugged between the pots and the lid when closed.  It may not look pretty to some, but it definitely works!  The key is to make sure the board is somehow secured.  I definitely wouldn't trust this method if you had a big empty case and the board was just going to be jostling around willy nilly.

More recently I've had a dozen of my pedals redesigned to have the boards mounted directly to the pots which I've heard people freak out about this more than my electrical tape usage (there fear being that over time the solder connections will vibrate loose or something silly like that), but once again never had a problem and have been doing it for a year now.

Ideally though I'm headed the way of a lot of other boutique builders (and a large percentage of bigger manufacturers) and plan on having practically everything board mounted so that they're easier to assemble, and once again, I have no doubt in my mind they will hold up to long term stress just as well as any other method.

Once again people freak out about the idea of solder connections or switches breaking / shaking loose over time, but this is totally a non issue with hand soldered gear; machine soldered (wave solder) perhaps if the quality control isn't there (heard this happen to a lot of marshall amps 10 years ago).

... and yeah, as someone mentioned earlier in this thread, adhesive is a no go with metal and standoffs.  I mean, there are some kind of industrial strength bonding agents, and if you goop enough, you can get a pretty decent fix going, but _that_ is something I definitely wouldn't gamble with.

[StereoKills]

I've used some "machinable aluminum epoxy" at work before that would definitely hold a standard aluminum standoff in place.

[Processaurus]

What would be the bee's knees is if there were a standoff built into the bottom of the pot, and the legs on the pot were pc mount, but thin wires with a bend in them.  Free idea, if anyone here happens to own Alpha!

[devi ever]

What would be the bee's knees is if there were a standoff built into the bottom of the pot, and the legs on the pot were pc mount, but thin wires with a bend in them.  Free idea, if anyone here happens to own Alpha!

You know what.  I bet you could TOTALLY jerry rig a standoff that you could put around the shaft of the pot so when you secure the pot down, it'd secure down with it.  Get what I mean?

There's gotta be some kinda little "L" bracket that would work well for that! 

[devi ever]

Something like this kinda : http://media.digikey.com/photos/Keystone%20Elect%20Photos/4332.jpg