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How to Disassemble a Vintage Big Muff
Here are instructions to disassemble a vintage Big Muff Pi pedal for maintenance. Though the designs and shapes of the various vintage 1970's era Big Muffs differ, you will find the components are similar for each. These instructions apply to models V1 through V6.
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1. Loosen the control knob set screws with a small screw driver and slide each knob off the three potentiometer (pot) posts.
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Note that some vintage or replacement control knobs may not have set screws and may simply be pulled off. WARNING - be very careful pulling knobs from the pot shafts as many vintage pots have plastic shafts that may break. If the knobs are very tight you may want to attempt to pull them off using the method shown above. Simply loop two shoe laces, or two strands of cord under the knob. One to the right and one to the left, then pull straight up. This method also works for guitar and amplifier knobs.
2. Remove the four enclosure screws for the top of the Big Muff. TIP - If screws are stripped, or you have missing screws, they can be replaced with 4x3/8" pan head phillips screws.
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3. Remove the top part of the enclosure from the bottom.
4. remove the three control knob nuts and 1/4" jack nuts and washers with a wrench, being careful not to scratch the surface of the pedal with the wrench. You can prevent scratching by placing a piece of paper, or post-it paper on the pedal around the nut.
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If the nuts are rusted to the pot or jack shafts, apply a few drops of light machine oil around the nuts and screws and let it soak into the rust for a few minutes, then attempt to uscrew the nuts again. You can also use spray contact cleaner around the nuts to accomplish the same thing. WARNING - if the nuts are rusted or locked to the pot shafts and turning the nut actually twists the whole pot, stop. You may break the pot contacts from the circuit board, damage the pot, or damage the circuit board. In this case you may have to insert pliers to grip the pot case while unscrewing the nut to prevent pot twisting. The same situation may occur when trying to unscrew the jack nuts. In that case, grip part of the metal jack inside the pedal with needle nose pliers to prevent it from spinning when unscrewing the nut.
5. Remove the two screws on either side of power or tone bypass switch. If screws are rusted or stripped they can be replaced with 4x3/8" pan head phillips screws.
6. Unscrew the ring bezel from the foot switch shaft with pliers, being very careful not to scratch the enclosure.
7. Gently push the two jack posts through the enclosure hole. The wires soldered between the the jacks and circuit board may be tough to bend, so push slowly so as not to break any wire solder welds.
8. Gently press each of the pot shafts and the foot switch shaft through the enclosure holes to remove the entire citcuit board assembley. Push each post equally a small amount at a time so they slide evenly and do not jam threads in the enclosure holes.
9. Remove the lock washers from the top of the pots. These are placed on top of the pots (under the enclosure) to prevent the pot from twisting when tightening the pot nuts. Note, some Big Muffs do not have these washers, but it is a good idea to add them.
9. Pull the whole curcuit board out holding it from the sides, being careful not to bend any of the circuit components. Reassemble the entire pedal in the reverse order.