Trouble with a replaced volume pot

Shark Bait

Active Member
I attempted my first soldering job. I have a Pioneer SX-636 that had a broken stem on the volume pot. I bought a replacement and learned hoe to de-solder and re-solder. It seemed like it all went well until I turned it on. The new volume pot starts at medium volume and goes to loud. It seems like it doesn't change for the first half of turning then from the halfway point it adjusts normally.

Any idea what I did wrong?

Thanks for the help
 
you may have bought the correct physical replacement but did not have the correct electrical
specs. volume controls are usually log devices where halfway point on rotation is not half
the total resistance.

look up volume, pots, tapers, etc. Verify with your service manual for your unit. it should say
something like audio taper.

otherwise as the above posters indicate it may be a soldering issue (maybe since reading
in between the lines, the control do vary the volume - just not correctly and these are
three legged fixed and you can't wire them out of order or backwards)

if you pull the new unit, using a VOM/DMM measure and compare the two. use any
two of the (two) pot's legs and consistently measure. have both face you in the same
front OR back orientation, pick the two left OR the two right. find halfway on both and
measure and compare. should be in close range.

this will tell you whether you have the correct replacement. or simpler to read the
description for the pot you bought unless you pulled it from another unit.

and even if you did pull it, there should be mfg markings (maybe) for component
value and/or product number - this last item allows you to check online.
 
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just looked at ebay - there are over 100 50K pots out there. I think you can find a solution.
some suggestions
1. consider using two of the three legs to match the original
2. ignore the loudness tap
3. mount 180 degrees from normal and use wires to connect pot to PCB
4. use different locking washer/nuts if the pot thread size is different
5. use a caulk compound inside original knob if shaft is smaller.

it would be a crime to allow a perfectly working pioneer from working for lack
of a nail...
 
The new pot looks basically identical to the old one. I am guessing I messed up with the solder. It was my first attempt.
 
so its a used pull from the exact unit, not a new one?. OK, that should be the proper taper then.

Now the question is whether all the connections are good, or if the pot itself is just a dud.
 
Could an incomplete solder cause that or is it more likely to be that solder ended up where it shouldn't have? Or, could I have messed up the board when I was de-soldering?
 
Could be either. I doubt you messed up the board if it doesn't look messed up though. When boards are damaged from solder work its pretty obvious.
 
I think I am going to take it apart again and recheck my solder spots. Maybe one of the contacts is not complete.
Thanks so much for the input. I would really like to manage to fix it myself.
 
CCW short for 'counter clock wise'.

What solder are you using. most use Kester 60-40. have a decent iron and tip and clean it?
 
I am a total newbie. Can you give me a little more detail? What does CCW stand for? Thanks for the input.
Apologies. CCW = counterclockwise. This end of a volume control generally goes directly to ground, so when the wiper (rotary contact) of the control is positioned at that end, it sees zero signal voltage. If you connect an ohmmeter between chassis ground and the CCW control terminals, it should read very nearly zero ohms.
 
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