MXR Distortion+ PCB Trace

Steve Mavronis · February 27, 2011, 11:26:26 AM

I'm just restoring this one to original condition to refurbish it. With the new PCB replica I made, trying to use close to what was in this 1980 unit. The op amp IC is a '80 Texas Instruments UA741CP with Malaysia stamped on top. In my stock of parts I do have is a Texas Instruments UA741CP with M701 (not sure if that's a date code) and Malaysia underneath so at least that is close. I have two small 1uF tantalum caps except they're yellow instead of blue. For the four ceramic caps I may try to re-use the originals since they don't appear to be damaged. I have two 1N270 germanium diodes that look identical to the originals.

After I get this together (hopefully today) and hear how it sounds, not sure if I should go beyond repair and mod the pedal to feature a red LED and DC jack. Maybe I'll keep 1980 spec integrity in this unit and if I want those added features, a complete separate clone pedal could be possible as a better option.

Steve Mavronis · February 27, 2011, 11:52:46 PM

I soldered parts onto my replica PCB. It was a pain but I de-soldered the four ceramic caps and put them on the new PCB. The pain part was one of them flipped out of my hand and it took me an hour crawling around on the floor until I found it! Anyway, the replacement PCB is ready to be attached after I clean the solder flux off the other side:

P.S. I made a spare PCB just in case I blow this one up!

Steve Mavronis · February 28, 2011, 07:52:51 PM

Well that's it for this thread I suppose. The verdict is in - It works!!!

\_m/

New DIY replacement board and refurbishment successful. Long live MXR Distortion+

Steve

newfish · March 01, 2011, 11:01:19 AM

wow!

*Very* neat re-build.

I think looking into photo-etch / ExpressPCB layouts is the way forwards.

Makes my hand-drawn PCBs look a little 'organic'...

Congrats on getting this little beast working again.

Steve Mavronis · March 01, 2011, 01:00:52 PM

Quote from: newfish on March 01, 2011, 11:01:19 AM
wow! *Very* neat re-build. I think looking into photo-etch / ExpressPCB layouts is the way forwards. Makes my hand-drawn PCBs look a little 'organic'... Congrats on getting this little beast working again.

Thanks for the compliment! I should have posted a completed gut shot too. That one was before the final 5 wires were soldered to the new PCB.

Any way that works for you is good; hand wired, vero, perfboard, etched PCB, etc. Back in the day when I was a kid before computers, my dad used to make printed circuit boards using clear plastic sheets and manually laying strips of thin black tape with tweezers to make complicated and sometimes double layer layouts by hand. It was kind of cool in a way. It would be very tedious, but I'd like to try it the old school way like he did in the 70's.

Ice-9 · March 01, 2011, 01:58:09 PM

Nice neat PCB there Steve.

Yeah back in my day at college we use to use clear acetate sheet and sheets of pads, lines, corners and Ic's you just rub them on the acetate. They were called letraset.

jplebre · July 01, 2011, 03:51:28 AM

Hi Steve!

Etched your layout, and worked like a charm...

In fact, worked too well as it was easy to put pieces in place and box it and nothing to debug!

This is brilliant thanks! now I have an almost replica in my pedalboard

jplebre · July 01, 2011, 04:17:05 AM

quick snap:

Steve Mavronis · July 01, 2011, 10:18:33 AM

Thanks! Nice job on your PCB etch. It's a 1:1 replica so MXR already did the debugging for us.

I'm happy making a replacement PCB for myself allowed me to restore my 1980 Distortion+ bringing it back to life from the dead!

ammalato · April 18, 2012, 09:57:28 AM

Just wanted to thank Steve and post an update. I got a hold of a vintage Script Logo MXR Distortion Plus enclosure in need of a little love. The paint is in excellent condition but the pedal was missing the bottom plate, Volume Pot and the entire circuit. Steve was kind enough to send me a replica circuit that he had etched for his project and I used it to re-build my pedal. Here are the finished shots... Works great.

Shot at 2012-04-18

Steve Mavronis · April 18, 2012, 11:25:35 AM

Glad you brought back to life your pedal and my board! Beautiful job.

Chrisfromiowa · October 09, 2017, 08:29:34 AM

I love reading the classics, like this thread. Does anyone involved still have the images? Thanks CfI

Fuzz-O-Rama · October 09, 2017, 05:22:15 PM

If you have a vintage pedal with everything in tact but the PCB has lost traces or IC pads I suggest you try to keep it stock. People want to pay big money for, let's say, a script Dist+. If you purchase some self-adhesive copper grounding tape and cut it with fly tying or cuticle scissors, you can replace the missing trace invisibly. For the IC pads, cut a pad shaped piece out of the tape, stick it in the right place and use a small awl to create the hole. Place the IC in and solder. Put a little vinegar on the new solder to add an oxidized patina and you have a perfectly preserved pedal. Try to find the closest foam to wrap the board in as the original foam. It almost always disintegrates.

space_ryerson · October 16, 2017, 04:20:15 PM

Quote from: Fuzz-O-Rama on October 09, 2017, 05:22:15 PM
If you have a vintage pedal with everything in tact but the PCB has lost traces or IC pads I suggest you try to keep it stock. People want to pay big money for, let's say, a script Dist+. If you purchase some self-adhesive copper grounding tape and cut it with fly tying or cuticle scissors, you can replace the missing trace invisibly. For the IC pads, cut a pad shaped piece out of the tape, stick it in the right place and use a small awl to create the hole. Place the IC in and solder. Put a little vinegar on the new solder to add an oxidized patina and you have a perfectly preserved pedal. Try to find the closest foam to wrap the board in as the original foam. It almost always disintegrates.

Weird side note: I have two pre-LED block logo MXR pedals (Dist+ and a dynacomp). The foam totally disintegrated. I also have a LED block logo MXR Dist+ pedal, and the foam is strangely intact. They must have switched foam sometime around then.

zombiwoof · October 17, 2017, 09:38:54 AM

I have a couple of old MXR pedals with disintegrated foam. When Dunlop started making the CS reissues with the foam in them, I emailed them to see if I cold buy a couple of foam pads from them for those pedals. They ended up sending me six foam pads for free!. I can't say that they would do that for everyone, but I may have been the only one to ask about that at the time.
Al

Fuzz-O-Rama · October 17, 2017, 03:49:42 PM

zombiwoof,
Your comment about dealing with Dunlop was heart warming. It is a lesson that a considerate person should never hesitate to "ask". So to express my gratitude to Dunlop, I would like to say that in my opinion, the Dist+ is the best overdrive ever made when used at a very low distortion setting. Don't take my word when it is easy enough to try. Full disclosure; I spent a great deal of time searching for the magical version of the 4558. That is what I love about pedals. So many pleasant discoveries. I just wish they didn't take a lifetime. So, when I have the time, and it is appropriate, I will post these things. As to the analog chip suffixes, they can denote plastic or ceramic, mil spec, temperature rating, etc.. Newer ones also specify Pb free. I hope I haven't bored people too much!

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MXR Distortion+ PCB Trace