Jap Jazz - Volume Pots - Advice

[Oggy]

Hi Guys

I've recently bought a 32" Medium Scale Japanese Jazz Bass from another member of this site - I absolute love it . To me it looks great, feels comfortable to play and sounds great - what more could I want?

Weeeeeellllllll - I have one minor gripe, not a train smash, that I hope some of you 'more techi' members will be able to advise / help me with.

Both of the Volume Pots only work for the last 20% of the full turn. The best way I can explain it is to liken the volume pot to the figures 1 - 10 on a clock face. With the marker at 1 there is no volume from the pickup (I'd expect this), I have to turn the pot up to 8 to get any signal / sound coming through, turning the pot from 8 - 10 gives a rapid rise in volume / signal. It's as though whatever the resistance value of the pot is between 8 - 10 should be what's applied to the pot on a gradual gradient from 1 - 10.

The above happens on both the front and rear pup volume control pots. The tone control pot behaves exactly as it should, with a gradual tone change right through the full turn.

Any ideas??

Thanks

Oggy

Edited August 30, 2013 by Oggy

[GregBass]

I thought volume controls only had two settings - off and full

Seriously, pots can be logarithmic or linear. It sounds as though you have the wrong type. Look to see if it says log or lin anywhere on the pots themselves, then replace with the other type of the same value.

[JapanAxe]

You can check the type of pot by disconnecting it from the circuit (including any connection from tag to pot body), setting it to half, and comparing the resistance from the middle tag to each of the other tags in turn. If they are about the same, it's linear; if very different, it's logarithmic.

If you are replacing pots, I suggest you take the opportunity to up the quality by fitting CTS pots.

[neepheid]

If the pots have their value stamped/printed on them then they might have a letter as well. A = audio/log, B = linear. C is reverse log, but that's another story you don't need to worry about that in a Jazz bass, but G&L tinkerers will know exactly what I'm on about So it'll be A500 for a 500k log pot, or B250 for a 250k linear pot etc.

[Oggy]

My thanks to [b]GregBass, JapanAxe[/b] and [b]neepheid[/b] for you advice, appreciated. It's been a decade or two since I had anything to do with PCB's or soldering irons, I come from an era of valve computers and very early OC44 and OC72 transistor circuits , anyone remember IN4148 diodes and 1/4W resistors .

I'll have a look on the Maplin site and see if I can get a wee bit of kit - Avo type measuring device and soldering iron + solder.

I do remember doing a bit at college, back in the late 60's / early 70's, using both Log and Lin potentiometers, during my apprenticeship. Could be a bit of fun to get back into a bit of tinkering.

Thanks again Chaps.

Oggy