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Registered Member #4081
Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139
Hello all, I bought a sony MHC RX80 stereo at a car boot (Bargain, £8 for a 90's beast) but it has a problem. The volume knob doesn't work. It is the kind that can be turned one way infinitely, so it's not a pot. I've looked for a service manual but can't find anything, does anyone know anything about these kind of volume controls and how the problem can be rectified? Cheers, Harry.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
yeah i would agree, but what does he mean "infinately in one direction" ? a normal encoder for front panels will rotate either CCW or CW infinately... right?
Registered Member #4081
Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139
Sorry, it can be turned infinitely in either direction. It doesn't matter which was I turn it, the effect on the volume is random, sometimes up, sometimes down, sometimes nothing at all. Any way to fix it?
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
If it has any effect on the volume at all, that's good, it means that something is happening.
If it's quadrature optical - a reasonable assumption - then opaque contamination of the slots or optics (say used by a heavy smoker?) could cause the symptoms you list, assuming it's not tracking across between high impedance connections, or broken wires making intermittent contact.
Examine the housing, clean it if it's dirty, probably won't fix it. Pull all the wires gently, if that stops it working one or more are broken, probably unlikely. After those simple checks, look for a way to break in, without breaking anything. Once apart, make sure all the slots in the slotted disc are clean, make sure the lenses on the optics are clean, and reassemble. I usually break something at this point, but hopefully YMMV.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Sulaiman wrote ...
The cheap mechanical rotary encoders only cost $1 to £1 so it would be worth replacing.
if he can find a physically close enough match, else its cleaning time, ive even carefully dremeld the back off, cleaned and reassembled a special one. Works just fine.
Registered Member #4081
Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139
Thanks everyone for the helpful replies! I'll give a clean with some oil or WD40 (I'll have to check it is non conductive) and see if that works. If it doesn't I'll disassemble it.
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Hi Fi knob failure
