How-To

How To: Replace Music Man Knob with MESA/Boogie MK1 Knob

The numbers on one of the knobs on a Music Man 112-RP-65 I was working on had faded, or had worn off, so I needed a replacement knob. After searching the Internet and only finding posts that were roughly 10 years, or more, old I followed a suggestion of using a MESA/Boogie knob that look similar but didn’t use a set screw to secure the knob to the shaft of the potentiometer. I took a chance and ordered two of the MESA/Boogie “Knob Large S Clip Insert – MK I”, part number 408109, knobs in the hope that potentiometers that it looked the knobs were designed for on the MEAS/Boogie web site used D shaped spring clips to hold the knob to the shaft of the potentiometer.

Figure 1 shows the top and underside of the MESA/Boogie knob.

Figure 2 is of the original Music Man knob and one of the new MESA/Boogie knobs:

The first step was to remove the D shaped spring clip from the MESA/Boogie knob using a screwdriver to deform the D shaped spring clip and then use needle nose pliers to remove the clip. Figures 3 and 4 show are of those activities.

The positioning tabs inside the knob for the D shaped spring clip were reduced in size using a ¼” drill bit and hand turning the bit until the hole was large enough to fit over the shaft of the potentiometer. A small “hobby” size drill chuck helped hold the drill bit. See Figure 5.

The knob was clamped to a piece of scrap from a TV stand to facilitate drilling the hole for the set screw in the knob. Also in the picture is the Music Man knob and the 8-32 machine screw used to verify the thread size of the set screw and the size of the drill bit needed to drill the hole for the 8-32 tap and the #29 drill bit that was used to drill the hole for the tap. The maximum depth to drill the hole was checked using a smaller drill bit and then that depth was transferred, less a small amount, to the #29 drill bit and the drill bit was taped at that point as a depth gauge. See Figure 6.

Once the knob was set up on the drill press, the Music Man knob was used to align the MESA/Boogie knob to drill the hole for the set screw at the same place on the MESA/Boogie knob both between the 0 and 10 and the distance from the top of the knob skirt. See Figure 7.

After the drill bit was lined up on the knob a pilot hole was drilled using a 1/16” drill bit, see Figure 7, then the #29 drill bit was used to drill the hole for the 8-32 tap. The picture is from after the hole was drilled, the knob was vacuumed off, and the knob and clamp was turned slightly for clarity. See Figure 8.

The knob remained clamped to start the 8-32 tap, see Figure 9.

Once the tap was most of the way through the hole the tap was extracted, the knob removed from the clamp, the tap started back through the hole, and then the tapping continued until the tap just touched the opposite side of the hole in the knob for the potentiometer shaft.

Figure 11 is of the tapped MESA/Boogie knob with the set screw from the Music Man knob.

Figure 11 is of the tapped MESA/Boogie knob with the set screw from the Music Man knob.