Cleaning and revamping an old pedal

SpikeVelvet · Post by **SpikeVelvet** » 19 Sep 2019, 21:20

I am fixing an old MXR Distortion+ for a friend. To the best of my knowledge it is a 1980. It needs a new battery snap and possibly a new pot. Apparently, these pedals were packed inside with some kind of foam, possibly for shock absorption. After almost 40 years it has eroded and turned into some really nasty stuff. The foam has broken down and is now a greasy film that is also quite sticky. Does anybody have any advice on how to clean this up?

Also some of the switch and pot terminals are showing some green corrosion. Is there a recommended way to clean this off? I have plastic safe contact cleaner but I don't want any surprises since the pedal is so old.

Are there some standard practices to refurbing an ancient pedal?

Any advice would be a big help. He doesn't want any mods just a restored pedal that works normally.

Thanks

plush · Post by **plush** » 20 Sep 2019, 08:47

SpikeVelvet wrote:I am fixing an old MXR Distortion+ for a friend. To the best of my knowledge it is a 1980. It needs a new battery snap and possibly a new pot. Apparently, these pedals were packed inside with some kind of foam, possibly for shock absorption. After almost 40 years it has eroded and turned into some really nasty stuff. The foam has broken down and is now a greasy film that is also quite sticky. Does anybody have any advice on how to clean this up?

I'd start with something less aggressive, like isopropanol, tooth brush, some q-tips and nonvowen napkins.

I've cleaned a lot of boards from that sticky ex-foam substance, sometimes it required some soaking and a bit of hard brushing, but eventually it'll all came off clean.

If no luck - some sort of a solvent or even acetone or DHM might help. They can corrode plastic parts and pcb coating when exposed to, so be careful.

SpikeVelvet wrote: Also some of the switch and pot terminals are showing some green corrosion. Is there a recommended way to clean this off? I have plastic safe contact cleaner but I don't want any surprises since the pedal is so old.

Clean them with isopropanol or acetone and a tooth brush. Remove all corrosion mechanically. Remove old solder with a solder wick or solder pump, then reflow them using fresh flux and solder.
Sometimes old corrosion around solder pads comes off when during the reflow. Don't mix old solder with a new one. Remove corrosion together with old solder, then apply new one.

Other non-solderable corroded parts may require some mechanical cleaning (hard metal brush, scraper or a file). Sometimes contact cleaner helps removing the oxidation. Sometimes not.

I always have a bottle of non-conductive PCB grade clear coat to finish and preserve the insides once I'm done cleaning them.

SpikeVelvet wrote: Are there some standard practices to refurbing an ancient pedal?

Any advice would be a big help. He doesn't want any mods just a restored pedal that works normally.

Thanks

Youtube, tons of videos about PCB reworking and corrosion removal. They all are aplicable to pedals.

Good luck.

SpikeVelvet · Post by **SpikeVelvet** » 20 Sep 2019, 13:25

Thanks, Plush.....That's a big help

Mcgarrah · Post by **Mcgarrah** » 25 Sep 2019, 13:09

What's the worst thing that can happen if the new solder is mixed with the old solder, Plush? How did the cleaning process go for you, SpikeVelvet?

plush · Post by **plush** » 26 Sep 2019, 12:58

Mcgarrah wrote:What's the worst thing that can happen if the new solder is mixed with the old solder, Plush?

It'd get angry and splatter all over your face and stuff...

In reality, mixing new and old solder sometimes makes new, crappy alloy, that might have quite different properties than the originals before the mixing. It might have poor adhesion - won't wet the pads even with tons of flux on top and can become brittle over the time, causing almost invisible cold solder joints which'd lead to malfunction.

Also, mixing leaded with lead free solder will shift or alter alloy's eutetic properties, making it very hard to work with.

Ice-9 · Post by **Ice-9** » 27 Sep 2019, 17:58

plush wrote:
Mcgarrah wrote:What's the worst thing that can happen if the new solder is mixed with the old solder, Plush?
It'd get angry and splatter all over your face and stuff...

In reality, mixing new and old solder sometimes makes new, crappy alloy, that might have quite different properties than the originals before the mixing. It might have poor adhesion - won't wet the pads even with tons of flux on top and can become brittle over the time, causing almost invisible cold solder joints which'd lead to malfunction.

Also, mixing leaded with lead free solder will shift or alter alloy's eutetic properties, making it very hard to work with.

Just use a leaded solder with the old solder and you have no problems at all (most diy's will use leaded solder). Using a new lead free solder is also fine but technique and temps is a little different. Either way there is no issues when done correctly.