Question on vintage MXR pedals

[glebert]

Picked up an old MXR Blue Box, circa 1974 for cheap, untested. Haven't done anything with it yet, but the circuit board is just sitting loose in the enclosure, It seems like it should at least be cushioned and electrically insulated. Anyone know how to treat it? TIA.

[The Dude]

I found this gutshot of one.



It looks like they mounted all the parts flat to the board so that no leads would be able to touch the back cover. The jacks were plastic, so that took care of isolating the underside of the board. If you are worried about it, it wouldn't hurt to cut a sheet of plastic to put between board and cover like Roland does in their pedals.

[Leo_Gnardo]

Picked up an old MXR Blue Box, circa 1974 for cheap, untested. Haven't done anything with it yet, but the circuit board is just sitting loose in the enclosure, It seems like it should at least be cushioned and electrically insulated. Anyone know how to treat it? TIA.

Old MXR's circuit boards were wrapped with a thin foam which apparently rotted away into sticky gobs of dust. Count yourself lucky to not have to deal with that. It was a friction fit into the box. What to replace it with? A sheet of plastic from a sandwich bag, maybe a couple of bits of foam weatherstrip to wedge the board into the box. Super gnarly tone on that Blue Box once you get it working. IIRC the Blue Box was featured on Led Zep's "Fool In The Rain" solo. Cheap is a good price. I heard those things sold for gold dust money mid 1990's, last time I ran across one.

Jump in at 3:50 to catch the Blue Box in action:

[Enzo]

I always saved my old credit cards, and those fake credit cards they send out with offers to sign up fir one. They are handy sized hunks of plastic or at least thick card stock. Good for this sort of thing.

[J M Fahey]

That.
Probably the no clue earlier owner junked the "packing material" or "piece of foam" he found inside as some "useless junk"

[DrGonz78]

First time I came across a piece of nasty deteriorating black foam was an old vintage Color Sound wah pedal. Had to remove all that stuff out of the pedal. I used a piece of styrofoam and I wrapped it up in medical cloth tape. Main thing in these situations is to get creative with out spending any money

[glebert]

That.
Probably the no clue earlier owner junked the "packing material" or "piece of foam" he found inside as some "useless junk"

Sounds like this is one time it is good that they didn't keep the original material in it, if it really breaks down so badly. This pedal was in a very interesting lot of gear I got, apparently they would take any gear that had a problem and put it up in the attic of this little house. Forty years later they decide to move and pretty much give it away to the first guy who shows up (which luckily was me). I didn't even know this pedal was in the box until I dug through all the old guitar cords, straps, etc.

[Mick Bailey]

The material I use for pedals is cut from ring binder covers. It's semi-rigid plastic and can be cut/scored/folded. Works really well.

[Helmholtz]

Here's my old Dyna Comp:

[Mark Hammer]

I have a pet theory that MXR had a tendency to use tantalum caps because they could be easily laid on their side and were often smaller than electrolytics of the era of same capacitance value. Part of what made this necessary was MXR's use of larger pots than are presently used, and the somewhat larger footswitches. All of that left precious little room for the loaded board in the enclosure, so it had to be as low profile as possible. You will note that all the caps and transistors on that Blue Box board are laying flat.

There's a lot of different materials one can use for insulating the copper side of a board from shorting out against the enclosure cover. I like to buy this stuff at Michaels or similar hobby shops that goes by the name "fun foam". It kind of looks like felt and is the same size as a square of felt, but is non-conductive foam. Cardboard inserts work fine as well.

[Leo_Gnardo]

There's a lot of different materials one can use for insulating the copper side of a board from shorting out against the enclosure cover.

Playing cards, if you have a "broken" deck. Or if you live where there are casinos, you can probably buy boxes full of used cards for peanuts.

I get ads in the mail made of a sheet of card stock laminated between plastic layers. None go to waste. Great surfaces to mix dabs of epoxy, or custom size insulators like what's needed here.