DIY Pedal Longevity Tips?

[bifbangpow]

Hey guys. I was wondering if you have any tips specifically related to insuring the longevity of your DIY pedals.  I know I personally have found that there are little things I can do that seem to effect the sturdiness of the build (like always making sure the insulation is 1/16th of an inch from the lug, no closer no further. so simple yet so important)  What are your tips for a great build?

[GibsonGM]

Great build = solid mechanical connections like jacks, any screws, GROUND TERMINALS....use stranded wire on pots & jacks when you can.

Proper wire routing, keeping low-level audio away from power.  Possibly use shielded cable for input jack up to 1st stage, to dodge noise.

Make sure the PCB is mounted in the enclosure in some way that won't EVER become degraded and cause shorts to chassis...standoffs, rubber pad, etc. 

IMO things like wire extending past insulation (why so simple and so important?)...as long as you are within the realm of common sense....aren't very important provided you are not flexing anything.  And you should not be flexing anything inside a pedal.

Someday the pedal WILL become 'compromised'...electros will fail eventually, and wire insulation will become brittle.  Some of that someone could fix  How long are we talking about here?   You should get 30 yrs. out of most pedals if you assemble them well.  Or half-assed, as long as a few considerations are met...

I build my stuff for me, and my lifetime.  If someone wants to come along later and renovate it, good for them   Same as we do for 70s stuff and all that.

[PRR]

> What are your tips for a great build?

Fix a LOT of stuff (not just pedals).

I mean a LOT of stuff. Clear out the back-log at the local repair depot. Find every problem. Fix it so that won't happen again.

It may not be the fast path to enlightenment. More a hard-knocks degree in hard knocks.

But you do gain insight into what types of things go wrong.

You also want perspective. Hardly anything I built decades ago is still useful. Some of it might still work if I dug it out of the landfill, but the reason for it is gone. 100 Year Service is probably not required. (Museum restorations maybe; though I know most don't come close.) I am learning how to make houses "last"; OTOH I am planning a "dog house" for my generator and realize there is no point in 30-year roof detailing for a machine that will probably crap-out in under 10 years.

[amptramp]

I must disagree with my colleague here - you may not want to use a pedal from 40 years ago and you may not be here 40 years hence, you should be able to use it with confidence that it will not fail then if you lose interest, sell it with some assurance that it won't come back as unsatisfactory with the buyer demanding their money back.

The first rule of longevity is derating.  By that I mean making sure components are used at a lower than rated voltage, current or power, depending on what is critical.  I like to use 25 volt electrolytics even in 9 volt pedals because the extra thickness of the dielectric adds some life.  You can download MIL-HDBK-217F to get the actual equations showing life versus component stress (where stress is the percentage of rated value is actually used in the circuit).  Establish derating rules and enforce them.  The NASA derating rules are surprisingly lenient, even more than the NAVSEA rules used by the US Navy, and they do not represent much of a hardship for designers.

The second rule is mechanical stability.  If anything is left floating, wires will move and snap eventually.  Components will short out or break.  If you are mounting a pot, use the anti-rotation lug.  If you have large knobs, they can cover the hole.  Don't want to do it because you are using chickenhead knobs?  Then expect chickenshit reliability.

Use jacks that can be reefed down for anti-rotation.  There are some very old telephone jacks that mount with screws.  These are ideal - they have their own anti-rotation.

Use strain reliefs where a lead has to come through a chassis.

You can use sockets to rotate through transistors and op amps - then when you find what you like, solder it in.  Sockets are never used in military or spacecraft equipment.  One Intel rep once said at a military meeting I was at that silicon never fails, just connectors.  He was almost correct - there are rare silicon failures but connector faults are par for the course.

Idiot proofing.  You have to protect the device from reverse voltage, overvoltage and excess output load (which may not kill the device but may cause unpleasant things like oscillation or changes to tone settings) and input/output overvoltages.  When I designed the Data Entry Display for the F-16, I used Transzorb protection diodes at both power inputs.  It saved our bacon in the early stages of the program.  We decided one Friday night at the 4:30 PM quitting time, that we would do the MIL-STD-704 tests for input supply power before we left for the weekend.  The unit had run perfectly well from the power supply in the test set but we had to try it with power from an external supply that could be varied through extremes of voltage and frequency.  We switched on and heard a bang and found the fuse blown.  Someone had wired the external 115 VAC 400 Hz input directly to the 5 VDC logic supply.  When we did the autopsy, we found the display had survived and the transzorb had protected the internal supply in the test set to the extent that only six of the 82 logic IC's had blown.  We were back in test within a week.  A schedule failure here would have left $35 million aircraft sitting on the ground, unable to be sold.  The only reason the test set blew was the unit was connected via a 3-foot long cable and this isolated the Transzorb elements from the test set, allowing the voltages to rise above the clipping voltage.

[Joe]

If you use decent jacks (like Switchcraft) and bend the washer quite a bit, then crank it down with the nut, you get a lock-washer effect and it is less likely to rotate. Also locktite will work anytime there are threads. Of course I never remember to do any of this.

[aion]

You can use sockets to rotate through transistors and op amps - then when you find what you like, solder it in.

You can also compromise a bit here and just solder one leg of the transistor or IC to the socket - that way it'll never come loose, but you can easily desolder it in the future. You are still relying on the mechanical connection, so not quite as optimal (militarily-speaking) as soldering the whole thing, but it's certainly much better than just leaving it in the socket where it could come out with enough shock.

[aron]

The biggest change was using a decent solid pedalboard. I rarely have problems now. When the pedals were loose - jacks got loose, when I used batteries - clips broke etc... But yeah, if it moves a lot it will probably break at some point. Pots will get scratchy, jacks will go bad. 9V clips will break. Oh and the stomp switches can go too. For those, I try it make it so I can change the parts out easily.

[PRR]

> The first rule of longevity is derating.

General electronics, that is important.

In *pedals*, most parts run far under the lowest ratings available.

Therefore I think your #2, mechanicals, could be #1 for pedals.

But it's all links in a chain. The detail that you didn't even think about is the one that will bite you in the end.

[Kevin Mitchell]

DIY Solder Mask

Something I find very useful. Really for the longevity of the circuit board.

[karbomusic]

DIY Solder Mask

Something I find very useful. Really for the longevity of the circuit board.

And to stop shorts from something landing on it which I've seen a few times. I use clear spray enamel which can be handled in 5 minutes or less.

[bifbangpow]

DIY Solder Mask

Something I find very useful. Really for the longevity of the circuit board.

Woe. This is the first I've heard of this!  I'm curious, does teh solder stick as well to the copper pads? I have issues sometimes on my home etched boards with keeping the solder from funning off the pad to begin with. So in my mind, painting over the board would make it ten times worse. But I'm anxious to try this.

[bifbangpow]

Use strain reliefs where a lead has to come through a chassis.

Strain reliefs?

[R.G.]

Anything that moves will eventually wear out or break. Pots, switches, jacks, and connectors come to mind.

Anything that flexes will eventually break unless the movement causing the flex is very small compared to the elastic limit of the material. Flex a circuit board and it or the solder joints will eventually fail. Solder creeps under pressure, and can crystallize from this and crack. Wires can flex successfully for a large number of cycles if and only if the flex is spread out over a long length of wire compared to the diameter. Even then, flexure can cause stress concentrations at the ends of wires where they're rigidly fixed and cause stress fractures. In small enclosures, wires may or may not be stiff enough to prevent flexing, or flexible enough to not be stressed. Goldilocks had a point.

Never fix a PCB rigidly in more than one plane unless you can fix it in one master plane, then soft-fix the other directions without causing **any** stress on the PCB.

Solder is not glue.

If it gets warm to your fingertip, you really need to consider whether it will die from thermal cycling. If it doesn't, ignore thermal cycling.

If the parts have exposed reactive metals (copper qualifies, as does iron and steel) they will oxidize.

It your foot can crush it or break off protrusions, it eventually will.

And then there's the Engineer's First Rule: if you can't make it last forever, make it easy to fix.

[thermionix]

Yep, it's the electromechanical components that tend to fail first.  Where possible, use Switchcraft jacks, CTS pots, and the "industrial" footswitches that Mammoth and SmallBear carry.  Avoid mounting these to PCBs.  No reason to go crazy with it, after all pedals are just toys, unlike guitars, tube amps, and F-16s.

[PRR]

> keeping the solder from funning off the pad

If your solder is "funning (running?) off the pad", that's a real problem.

Copper not CLEAN.

Lack of proper flux.

Excess solder.

Bad (for our purpose) solder.

[Jdansti]

Use strain reliefs where a lead has to come through a chassis.

Strain reliefs?

I think strain relief is what my mother needed when my brothers and I were kids.

Strain relief is the act of making sure that a wires and cables that pass through the wall of an enclosure can't be accidentally yanked out. Sometimes strain relief incorporates bend relief. There are devices to lock a cable or bundle of wire in place so it can't be pulled out. Take a look at any device that has a cable permanently attached and you'll see the strain relief device. Here's a good article on the topic.

http://heyco.com/blog/strain-relief-indispensable-item-complete-cable-protection/

We don't have the need for strain relief too much on stompboxes except internally to keep wires from moving around. We normally see it on the power cords on amps and on guitar and mic cables.

[armdnrdy]

Thanks for clarifying that John.
I thought he meant Stain Relief!

[Jdansti]

Thanks for clarifying that John.
I thought he meant Stain Relief!

Right-You need that when you spill a beer on your amp! 

[bluebunny]

Thanks for clarifying that John.
I thought he meant Stain Relief!

Stain Relief is what John's mother needed when he and his brothers were kids.   

[Kevin Mitchell]

Woe. This is the first I've heard of this!  I'm curious, does teh solder stick as well to the copper pads? I have issues sometimes on my home etched boards with keeping the solder from funning off the pad to begin with. So in my mind, painting over the board would make it ten times worse. But I'm anxious to try this.

You may be using too much solder. The coat melts away when heated so I'd assume your problem will still happen. I posted that thread not too long before you started this one I'm surprised you missed it!