PROBLEM
Pot shaft broken off
C50K dual, 3mm D-shape, green housing (RK series, I think)
Otherwise unit is fully functional.
Anti-log pots are not that common and dual-ganged C-law pots even more so. Also not so common are 3mm shafts, and if that wasn't enough already, a D-shape with the flat side facing upward is yet another challenge. Anyway, that pot was very likely bulk custom-made by BSS.
I couldn't find a replacement easily, not in old-parts stores here in Japan, not online.
(I probably didn't look hard , closely or long enough, , but time is a factor after all -- and so is cost.)
SOLUTION(s)
- The idea of using a simple extender wouldn't have worked cos simply too long.
- Using another dual C50K might have worked, but leads would have needed to be wired to the PCB. Space behind the faceplate in those BSS units is very tight. And just a different knob...
- Use a dual log pot wired in reverse, eh, not really.
- So, inspired by another thread I drilled a 3mm hole vertically into a 6mm shaft for inserting the broken-off 3mm shaft. Unexpectedly, drilling the hole worked out smoothly but it still didn't solve the problem (for the 'how' and 'why' see below).
- So I finally set out to replace the entire shaft itself of that broken pot to make the otherwise functional dual C50K work again.
TOLD IN IMAGES
...cos it's easier to show than to describe in words
_____________________________
Drill guide (RC axle extension)
Drilled shaft
Shaft inserted
Fit not
Pot shaft broken off
C50K dual, 3mm D-shape, green housing (RK series, I think)
Otherwise unit is fully functional.
Anti-log pots are not that common and dual-ganged C-law pots even more so. Also not so common are 3mm shafts, and if that wasn't enough already, a D-shape with the flat side facing upward is yet another challenge. Anyway, that pot was very likely bulk custom-made by BSS.
I couldn't find a replacement easily, not in old-parts stores here in Japan, not online.
(I probably didn't look hard , closely or long enough, , but time is a factor after all -- and so is cost.)
SOLUTION(s)
- The idea of using a simple extender wouldn't have worked cos simply too long.
- Using another dual C50K might have worked, but leads would have needed to be wired to the PCB. Space behind the faceplate in those BSS units is very tight. And just a different knob...
- Use a dual log pot wired in reverse, eh, not really.
- So, inspired by another thread I drilled a 3mm hole vertically into a 6mm shaft for inserting the broken-off 3mm shaft. Unexpectedly, drilling the hole worked out smoothly but it still didn't solve the problem (for the 'how' and 'why' see below).
- So I finally set out to replace the entire shaft itself of that broken pot to make the otherwise functional dual C50K work again.
TOLD IN IMAGES
...cos it's easier to show than to describe in words
_____________________________
Drill guide (RC axle extension)
Drilled shaft
Shaft inserted
Fit not
