Help with fixing an old Distortion+

[Tone Slinger]

Ok,its a '79 model that belongs to a buddy of mine. He had it in storage since the mid '80's. He let me borrow it. When I got it home and opened it up, well, I immediatly knew that the battery had been in there the whole time and had leaked ALL over everything. The foamy looking wrap that protects the board was all but disolved. A lead on the battery connector was corroded through. I fixed that and took a long time cleaning it with q-tips and sticking toilet tissue all in it and leaving it to soak up all that acid, etc.

So, it works, but is very scratchy, staticy and you have to manipulate the in/out jacks a bit to get it to 'sound'. It doesnt work at all sometimes. So, without overhauling everything, where should I check first ? The jacks, the switch, the wires themselves, etc ?

[Haze13]

Pots and If you can upgrade Jack, this will be nice... Electrolytic caps may be. They don't last for ever. Every thing will be cost to you 5 buck on Ebay + free shipping.

[Tone Slinger]

Thanks man,I'll swap out the pots first and go from there.

[TWANGGG]

Just a thought before you go to the trouble of sourcing/replacing pots, have you tried to trouble shoot it by just jumpering the pot terminals?

[Tone Slinger]

How do I do that exactly ?

[TWANGGG]

mxr_dist+_schem (Custom).jpg (43.28 KiB) Viewed 1701 times

Well from this schematic it looks like you could bypass the output pot by putting a jumper (wire with a couple of alligator clips) between the center terminal of that pot and the terminal with the noted purple wire. That would be the same as the output being cranked wide open and might help you eliminate that pot as a source of your trouble.

For the distortion pot if you disconnect the black wire from the center terminal it should be maxed, and again may tell you something about the condition of that pot.

Sounds like that battery acid sitting in there messed it up pretty well. You mentioned about the battery wire being corroded through so wonder about elsewhere like the contact points on the in/out jacks. Like Haze13 said considering the corrosion issues you may just wind up needing to replace pots and jacks...

[Tone Slinger]

Thanks man, I'll give it a try

[vanhalen5150]

Pull back some of the insulation on the board wires. Are they green colored under the insulation? Some of the old MXR's has a copper based wire that corrodes over time. Turns to dust. I have an old Phase 90 that did that. Once I replaced every wire it worked great.
Id probably just go ahead and replace them anyways.

[stef]

I'd replace everything that was mentioned in this thread: electrolytic caps (maybe ceramic caps, OP amp and diodes too especially if the acid leaked on them), wires, pots and jacks. You should be done in an hour so having almost brand new pedal.

I did something similar on a DOD250 pedal several years ago with my mediocre soldering skills at the time and that pedal still works flawlessly.

[Omn]

The foam in these pedals will disintegrate over time. So I would guess you have two causes (one, if we just use time ); acid from the battery and foam decay. The acid leakage may be minor or limited...
Action or solution would be the same so my post is rather redundant. Sorry for that.

That foam thing is a real mess. Sticky and all over the place.

[guitar007]

I found that CLR works pretty well when removing battery acid and corrosion. Good luck.