I like many have had the misfortune of a broken MC2105 speaker on off switch, Mcintosh part number 146-103. The original, Clarostat 20 had long given up.
Use the following info at your own risk.
Knowing this was just a simple DPST throw, I began looking around for a suitable replacement. In looking at the spec sheet for this particular rotary switch, I found that mouser had one that worked, but it was too long. But, researching the order codes, I found that the unicorn exists, albeit, it requires a light filing down of the shaft in order to fit the knob; otherwise perfect.
The Brand is C&K, part number is A21405RNZQ
You'll notice the original clarostat is rated 3A @ 125VAC, while this outwardly is 2.5A @ 125VAC. Looking at the spec sheet you'll notice it can carry 5A. Assuming that an MC2105 puts out 29v @ 8 ohms, thats roughly 3.6a @ 29v or 5.125a @ 20.5 (4 ohm). Considering that unless you pegging your amp out, you'd likely not hit those levels anywhere near continuously. After installing, I fired up the amp and ran it hard for about an hour, and according to the laser temp tool, it was 1F above ambient. Not enough for me to be worried.
At any rate, I hope this helps others. Mouser is sold out of this right now, but does have a similar part, with a longer shaft that you'd have to cut down. It also has PCB type terminals on the back side, but is workable. That one is part number A21415RNCQ.
https://www.mouser.com/datasheet/2/60/ckci_s_a0001220822_1-2263264.pdf
Jumpered original vs new:
Soldered in place: gray wires from transformer go to pin 4 and pin 10. Purple/brown to A, and Purple+White Stripe/Brown go to Pin C. I had to heat shrink my cables due to the previous original wires being too short after being jumpered previously.
Installed. Note that the locating pin doesn't line up quite right to make it work with the layout of the silk screen so you'll need to orientate it accordingly for the best alignment. Notice where I filed the flat portion of the switch pole down to fit the knob. Took about 10 minutes with a file to get it right.
Side by side - the white line gives you an idea of why you need to file it down:
Use the following info at your own risk.
Knowing this was just a simple DPST throw, I began looking around for a suitable replacement. In looking at the spec sheet for this particular rotary switch, I found that mouser had one that worked, but it was too long. But, researching the order codes, I found that the unicorn exists, albeit, it requires a light filing down of the shaft in order to fit the knob; otherwise perfect.
The Brand is C&K, part number is A21405RNZQ
You'll notice the original clarostat is rated 3A @ 125VAC, while this outwardly is 2.5A @ 125VAC. Looking at the spec sheet you'll notice it can carry 5A. Assuming that an MC2105 puts out 29v @ 8 ohms, thats roughly 3.6a @ 29v or 5.125a @ 20.5 (4 ohm). Considering that unless you pegging your amp out, you'd likely not hit those levels anywhere near continuously. After installing, I fired up the amp and ran it hard for about an hour, and according to the laser temp tool, it was 1F above ambient. Not enough for me to be worried.
At any rate, I hope this helps others. Mouser is sold out of this right now, but does have a similar part, with a longer shaft that you'd have to cut down. It also has PCB type terminals on the back side, but is workable. That one is part number A21415RNCQ.
https://www.mouser.com/datasheet/2/60/ckci_s_a0001220822_1-2263264.pdf
Jumpered original vs new:
Soldered in place: gray wires from transformer go to pin 4 and pin 10. Purple/brown to A, and Purple+White Stripe/Brown go to Pin C. I had to heat shrink my cables due to the previous original wires being too short after being jumpered previously.
Installed. Note that the locating pin doesn't line up quite right to make it work with the layout of the silk screen so you'll need to orientate it accordingly for the best alignment. Notice where I filed the flat portion of the switch pole down to fit the knob. Took about 10 minutes with a file to get it right.
Side by side - the white line gives you an idea of why you need to file it down:
