I've got a little micro hi-fi system on my desk here which I use to play the audio from my PC through, but it's over 10 years old now, and the volume knob stopped working properly..
Rather than being a nice smooth scale up and down with values of 0 to 50, it turned into the equivalent of a random number generator, which is *really* handy at night when you want to turn the volume down, and it goes right up to full, wakes half the street up, and leaves my ears bleeding..
Not ideal, as you can imagine..
Now, given the state of consumer electronics these days, I had little to no hope of ever getting the thing fixed, but I thought I'd give it a go anyway, on the assumption that it was probably a dodgy potentiometer, which with any luck I could get a replacement for, getting to it would probably be another matter though.
To my surprise the JVC UX-1000 is a surprisingly well built bit of kit, with it coming apart in a PC style way - take the screws out of the back, release the side panels, undo a couple of cables and take the front off..
This all comes apart okay, and I get to the front control board, and sure enough, there's the "pot", in the middle of the board, and luckily it's not a surface mount component, so out comes the soldering iron, and various apparatus.
After I freed it from the board I hooked it up to my Dad's old analogue multimeter to check out how knackered this ALPS 740N "pot" was. As I turned the shaft of the "pot" around, the multimeter needle did the equivalent of a squirrel on speed at a rave, bouncing around all over the place.. Not good I thought..
Dad had a look too, but he had the sneaky suspicion that this wasn't actually a potentiometer, but a rotary pulsing switch.. Oh bugger I think, where the heck am I going to get a new one of those to fit?
So while I'm googling for a replacement to no avail, I undo a couple of little clips on the switch, and the whole mechanism comes apart..
Into three nice big bits, and not firing a myriad of tiny components everywhere! Result!
So I clean up the switch contacts and surfaces up with a bit of cloth, put it all back together (which was also a surprise), and tested it on the multimeter again..
Yup, it now pulses at a regular interval with a constant turn of the shaft.. Cool Beans!
I then solder it back onto the board, and reassemble the hi-fi..
No bits left over!
Plugged it in, and turned it on.. It didn't explode!
Connected it up to the PC, and behold, sound came out, and the volume worked!
Feeling quite smug, I then looked at the display.. which now resembles digital vomit, displaying random things with each button press..
Nuts!
Oh well, I'm not chancing it again, at least the volume works now![]()


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