Alpha board mounted pots woes.

[~arph]

I designed myself a nice PBC, first time with board mounted pots.
I got the long legged ones from smallbear, built up the PCB



Damn that looks nice...

Then, two issues struck me when fitting it in the enclosure.

1. The legs are too long for a Hammond B!
2. The pot centers are closer then I thought they would, the little tab extends outwards a bit more then I thought before the 90 degree bend.

I do realise these are my own errors, I should have measured them a bit better and I should not have gone by the GM eagle library for a drill template.
I just wanted to get this out here so someone might read this and not make the same mistakes as I did.

I did catch one sneaky bug, and that is if you want to use board mount pots and use the gm-eagle library. Be sure to flip pins 1 and 3 otherwise all your pots will work backwards!

As impatient as I was I did some metal bending and tape isolating and now everything fits.
Any smart tips on how to shorten the legs a bit? Just cut them of and use a large wire clipper to shape up the end so it fits the board holes again?

[spargo]

I've found a few of the components in the GM library to not be totally accurate, either in size or hole size.  I measure and make my own components with a micrometer I got on eBay for $10.

When I've used board mounted pots in the past, what I've done is use the short legged ones but actually flip the board around from where you have it and mount them on the other side.  That way when you open up the back of the pedal you can easily swap your socketed chips as well.  Of course, this would require you flip the holes around on your current board design or require different drilling.

[Galego]

The regular pcb mount alphas with the shorter legs have the perfect length, once you straighten them out:



The backs will rest on top of the IC's with sockets and they leave plenty of room in a 1590B.

[~arph]

Yeah so either I stop socketing my IC's and flip the PCB or modify the pots...(bending, resizing..)
Just for the record, the BB is a little higher. Do the long shaft pots fit there?

[smallbearelec]

As you now realize, this is where you get into serious design issues and having to think in three dimensions...hardest part of rolling your own, but very satisfying when everything fits together! Possibilities:

--If you like the 42 Series (long-pin), I know that some commercial builders put a slight bend in the middle of the pin to effectively shorten it. They typically have an assembler do it in a jig so that it's consistent in angle and position.

--In some cases, a taller enclosure like the 125-B or 125-BB is the ticket.

[~arph]

I like the long series. Putting a small bend in would be fine, but in this case it had to be huge bends because I also had to straighten them out as I had width issues too. They look like limbo dancers now  

The next version of this pedal has five pots and will be in a BB enclosure, so I think I'll be fine there. Building a bending rig sounds like a good plan if I have to do series of them. (I have access to a welding machine now, so perhaps some modified pliers can do the job quick.. insert pot, squeeze, done).  I still dont want to give up the option of cutting the ends and reshaping them to fit the PCB again. The pins are made of a quite soft metal.

[Govmnt_Lacky]

@Galego..

I always wondered about your builds. Although I do like the "all-in-one" boards that you design, I still do not know how you get the Input/Output jacks to screw down FLUSH to the enclosure 

After all, all of the enclosures that I have used a tapered on the sides (Hammonds, 4Sites, etc.) and there is always a slight angle to the jacks when secured. Do you use enclosures that are NOT tapered?

[~arph]

My guess:
First you mount the jacks, flush. Then you solder the board. This way the jacks are flush to the enclosure, but slightly angled at the board.

[defaced]

I did catch one sneaky bug, and that is if you want to use board mount pots and use the gm-eagle library. Be sure to flip pins 1 and 3 otherwise all your pots will work backwards!

They're probably intended to be mounted on the bottom of the board, not the top.  I've never used that footprint in his library, but that's my guess anyway.  Though now that you bring this up, I'm going to check the layout of an amp I'm doing with the gm front facing board mounted jacks. 

[~arph]

Yeah I just wanted to give a nod to everyone to double check their board mounted pot pinouts.

[Fender3D]

@Galego..

I always wondered about your builds. Although I do like the "all-in-one" boards that you design, I still do not know how you get the Input/Output jacks to screw down FLUSH to the enclosure 

After all, all of the enclosures that I have used a tapered on the sides (Hammonds, 4Sites, etc.) and there is always a slight angle to the jacks when secured. Do you use enclosures that are NOT tapered?

2 Cliff jack sockets won't fit in a 1590B side by side without a little filing, and not just for the tapered sides...

[EATyourGuitar]

use the short legged ones but actually flip the board around

the king is just to keep it from touching metal. there is an alpha 16mm solid shaft pot under there

[Scruffie]

Yeah, back board mounting is probably the better way to go about things, you can still see the component side when the effect is mounted/get to trimmers etc and there's no worrying about any components being too high for the pots.

[Beo]

I've been working through these issues with my design projects as well. I'm also using short pin pots mounted on the trace side, so that the components are visible/accessible when you open the box. Not only do you need to be careful with the pot pinout in your layout, but you also have to be careful with the layout itself. You won't be printing the layout mirrored if the traces face the top of the box... need to get left and right figured out carefully.

[cloudscapes]

I think I'm gonna start using tiny pots, now.

they roughly have the footprint of these encoders:

[Galego]

@Galego..

I always wondered about your builds. Although I do like the "all-in-one" boards that you design, I still do not know how you get the Input/Output jacks to screw down FLUSH to the enclosure 

After all, all of the enclosures that I have used a tapered on the sides (Hammonds, 4Sites, etc.) and there is always a slight angle to the jacks when secured. Do you use enclosures that are NOT tapered?

First you have to slightly trim the ends of the jacks where they touch each other. Like Govmnt Lacky said, together they wont fit inside a 1590B enclosure. I use an X-Acto knife.
There's no secret other than that, even if the sides of 1590B enclosures are slightly tapered (Hammond 1590B are pretty straight, BB not so much), they're not enough to represent any issues.