Tone pot problem
Kari
Hi,
Just noticed a weird thing on my Ibanez SZ520. It has a master tone and if I
turn it down to zero it cuts the signal almost completely i.e. there is
_very_ little sound. I have to turn the amp to even hear it.
I had a look at the wiring and it seems ok (this is the one thing I
_haven't_ changed on it): the wire from the pickup selector switch is
connected to the center leg (?) on the pot and then from the same leg to the
output jack. One of the other legs is wired to the ground via a capacitor.
The third leg is not connected to anything.
Any thoughts on what's wrong, fault pot or cap? Something else?
Cheers,
Kari
Baz Goodman
wrote:
i had a problem like that with my cruser, when i turned the tone down
to bass it cut the sound out completely and wudn't play... the reason?
the tone knob was earthed when it shouldn't be...someone did some
dodgy wiring.tho its fixed now thanx to chris, oh yeh let me take this
oppitunity to thank yu chris :) cheers!, ne way this may or may not be
the problem im just throwing up ideas
--
We all walk alone in this life, but lets play guitar on the way :D
__
Chris Bolus
wrote:
>
Wiring sounds right; the only question in that case would be the value
of the capacitor. It's probably too high.
If you can disconnect one end it should confirm this; in that case there
should be no noticeable difference when you adjust the pot.
I'd expect it to be between 1 and 10 nanofarads. If there are any
numbers or coloured stripes on the capacitor, tell us what they are, we
should be able to translate!
--
Chris Bolus (change o to zero to reply by email)
I love cheap guitars, me. But I'm learning to appreciate expensive ones!
John
Wiring sounds right; the only question in that case would be the value
of the capacitor. It's probably too high.
If you can disconnect one end it should confirm this; in that case there
should be no noticeable difference when you adjust the pot.
Surely if he disconnects the capacitor, the whole tone control
electronics will out of circuit, so it won't prove anything. Or am I
missing something?
John.
nog
Maybe we both read it differently but that's what I thought Chris to have
said?
--
Peter
John
The capacitor in the tone control circuit will act as a short circuit at
certain frequencies (no change in tone) and attenuate certain other
frequencies (reduce higher frequencies). So it can either be an open
circuit capacitor, or of the wrong value (attenuating by too much so it
affects all frequencies). But disconnecting it with prove neither of
these things.
John.
Chris Bolus
Not so. Disconnecting it will eliminate any fault that may exist in the
other parts of the wiring - not that I think there will be - as the
component which is supposed to take the signal to ground will be out of
the picture. But it sounds likely to me that it's simply too large a
value for the circuit and is hence taking too much of the signal to
ground.
Steve at fivetrees
news:sBDNg.8537$s4....@newsfe3-win.ntli.net...
>
> The capacitor in the tone control circuit will act as a short circuit at
> certain frequencies (no change in tone) and attenuate certain other
> frequencies (reduce higher frequencies). So it can either be an open
> circuit capacitor, or of the wrong value (attenuating by too much so it
> affects all frequencies). But disconnecting it with prove neither of these
> things.
Not quite, John. Let me see if I can do better.
A conventional (passive) tone control consists of a pot and a capacitor in
series, connected between the signal path and ground. When the pot is at max
value (let's say it's infinite), the capacitor is effectively out of
circuit, and has no effect. When the pot is at min value (0R), the capacitor
is connected directly between the signal path and ground. The signal path
has a source impedance, and this in combination with the capacitor forms a
low-pass filter. Basically, the capacitor has a lower impedance for higher
frequencies - i.e. the higher the frequency, the more of the signal gets
bled to earth - i.e. taken out of the signal. Conversely the lower the
frequency, the less signal gets bled to earth. For an infinitely high
frequency, the capacitor will act as a short circuit - and you'll get no
output, since you've shorted out the signal path.
To me, Chris' suggestion was sensible. By breaking the cap/pot connection,
the tone control should do nothing. If the fault persists, it's not the
capacitor.
Kari
"Steve at fivetrees" <st...@NOSPAMTAfivetrees.com> wrote in message
news:rpudnaIAKcn...@pipex.net...
<snip>
>
> To me, Chris' suggestion was sensible. By breaking the cap/pot connection,
> the tone control should do nothing. If the fault persists, it's not the
> capacitor.
What I forgot to mention in my original post was this: there was barely any
change in tone when I turned the tone pot. Read further...
First, out came my simple multimeter. I got a reading of about 450k on the
pot, which is ok...but I also got about 10k resistance through the cap
itself. Is that what it is supposed to do?
Then, I decided to try disconnecting the cap. I tried to have a closer look
at the cap, but it was placed tightly inbetween the legs and the main part
of the pot so I had to twist it up to see any of it (and doing so I moved
bit of the wiring as well). It didn't have a value on it, but a code
'2A223T' or something, very difficult to see, the 2s could be Zs and the
last letter could be a J.
Anyway, I plugged the guitar into my POD to listen to the sound once more so
I could hear the difference after I disconnected the cap....but now it was
ok. There's a smooth change in the tone when I turn the pot and it does not
cut off in zero.
Any ideas? :-) Was it just a cold solder joint or still a faulty cap that
decided to work properly again once gave it a bit of twist?
So it seems to be fine now but I might replace the cap anyway.
Cheers,
Kari
Guitone
Hi,
You say the one thing you *haven't* disturbed is the wiring so have you
disturbed the pots in any way? Some guitars have a conductive 'spray on'
coating for screening inside the control cavity. If any of the pot contacts
short to this screening then it affects the operation of the electrics.
Hope this helps,
TonyW.
Woody
> "Steve at fivetrees" <st...@NOSPAMTAfivetrees.com> wrote in message
> news:rpudnaIAKcn...@pipex.net...
> <snip>
> >
> > To me, Chris' suggestion was sensible. By breaking the cap/pot connection,
> > the tone control should do nothing. If the fault persists, it's not the
> > capacitor.
>
> What I forgot to mention in my original post was this: there was barely any
> change in tone when I turned the tone pot. Read further...
>
> First, out came my simple multimeter. I got a reading of about 450k on the
> pot, which is ok...but I also got about 10k resistance through the cap
> itself. Is that what it is supposed to do?
No, but you are not measuring the resistance of the cap, just a path
around it.
> Anyway, I plugged the guitar into my POD to listen to the sound once more so
> I could hear the difference after I disconnected the cap....but now it was
> ok. There's a smooth change in the tone when I turn the pot and it does not
> cut off in zero.
>
> Any ideas? :-) Was it just a cold solder joint or still a faulty cap that
> decided to work properly again once gave it a bit of twist?
Could well be a dry joint or some bad connection.
--
Woody
Jose de las Heras
"Kari" <kvieri...@xxxyahoo.co.uk> wrote in message
news:lJGNg.37648$Nb2.7...@news1.nokia.com...
>
[...]
> Then, I decided to try disconnecting the cap. I tried to have a closer
> look at the cap, but it was placed tightly inbetween the legs and the main
> part of the pot so I had to twist it up to see any of it (and doing so I
> moved bit of the wiring as well). It didn't have a value on it, but a code
this sounds like you were getting connections where you should have not, and
the situation was corrected when you moved the cap/wiring.
I've had fun in the past rewiring an old strat copy, where everything worked
okay until I screwed the pickguard in... I had installed extra switches and
it was pretty tight... I had also put some aluminum foil as screening, and
some of it was touching bits it shouldn't when the pickguard was mounted...
if you suspect this sort of mis-contact, it would be worth using some
electrical tape to insulate the legs of the capacitor or other cables in the
vicinity that may have long exposed portions, just to make sure they don't
misbehave again.
Jose
--
Musha ring dum a doo dum a dah - www.mcnach.com
Current fave guitar: Fender 'Sambora' Stratocaster
Fender Stratocaster - part coffee table, part spaceship.
E_G
I just want to tell you that the potentiometers connected in any guitars are
as follow
Volume pot is to wire in parallel and tone pot is to wire in serial
so the only pot that has a connection to the ground is the volume pot.
In other words, one shouldn't have a tone pot with any legs to the ground!
the capacitor in connection with the tone pot act as a filter and only the
capacitor is grounded.
so my advise would be that you remove one leg to the capa and see what
happens. Then bridge the pot and see what happens. By doing so you should
have a better idea of your problem.
--
Erick Ferini
http://www.guitarapproach.com/
"Kari" <kvieri...@xxxyahoo.co.uk> wrote in message
news:lJGNg.37648$Nb2.7...@news1.nokia.com...
>
Steve at fivetrees
> news:rpudnaIAKcn...@pipex.net...
> <snip>
>>
>> To me, Chris' suggestion was sensible. By breaking the cap/pot
>> connection, the tone control should do nothing. If the fault persists,
>> it's not the capacitor.
>
> What I forgot to mention in my original post was this: there was barely
> any change in tone when I turned the tone pot. Read further...
>
> First, out came my simple multimeter. I got a reading of about 450k on the
> pot, which is ok...but I also got about 10k resistance through the cap
> itself. Is that what it is supposed to do?
The 10k you're seeing is the pickup(s). You're measuring between ground and
the signal path.
> Then, I decided to try disconnecting the cap. I tried to have a closer
> look at the cap, but it was placed tightly inbetween the legs and the main
> part of the pot so I had to twist it up to see any of it (and doing so I
> moved bit of the wiring as well). It didn't have a value on it, but a code
> '2A223T' or something, very difficult to see, the 2s could be Zs and the
> last letter could be a J.
"223" could well be 22nF - i.e. 22 * 10^3.
> Anyway, I plugged the guitar into my POD to listen to the sound once more
> so I could hear the difference after I disconnected the cap....but now it
> was ok. There's a smooth change in the tone when I turn the pot and it
> does not cut off in zero.
>
> Any ideas? :-) Was it just a cold solder joint or still a faulty cap that
> decided to work properly again once gave it a bit of twist?
>
> So it seems to be fine now but I might replace the cap anyway.
It sounds like the cap was shorted out, possibly by the twist. If so, your
tone pot would be acting as a volume pot, which was what you were seeing. At
min value, it was shorting the signal path to ground.
Cliff
It sounds like the leg of the cap that is soldered to the tone pot may
have been earthing on sometime. May of been the pot body or a bare
wire. As suggested by another - a bit of insulation may be a good idea.
Can't be sure but, with all those twos in the stock code, the cap is
probably a 22nF (0.022uf). This is pretty standard on most modern stock
guitars.
Cliff
Cliff
Snap - I loose, you beat me to it by 8 minutes :-)
Cliff
icarusi
news:lJGNg.37648$Nb2.7...@news1.nokia.com...
> Any ideas? :-) Was it just a cold solder joint or still a faulty cap that
> decided to work properly again once gave it a bit of twist?
The pot tag is often just a rivet connection to the pot internals and can
easily go open circuit with mechanical stress. In your case it sounds like
the cap wire was shorting out the circuit. Adding some insulating sleeving
to those wires may avoid that in future if there isn't room keep the wiring
permanently separate.
icarusi
--
remove the 00 to reply
JNugent
> "Kari" <kvieri...@xxxyahoo.co.uk> wrote:
>>Just noticed a weird thing on my Ibanez SZ520. It has a master tone and if I
>>turn it down to zero it cuts the signal almost completely i.e. there is
>>_very_ little sound. I have to turn the amp to even hear it.
>>I had a look at the wiring and it seems ok (this is the one thing I
>>_haven't_ changed on it): the wire from the pickup selector switch is
>>connected to the center leg (?) on the pot and then from the same leg to the
>>output jack. One of the other legs is wired to the ground via a capacitor.
>>The third leg is not connected to anything.
>>Any thoughts on what's wrong, fault pot or cap? Something else?
Did you buy the guitar new or s/h? Had anyone else had a chance to mess
about with it?
If you bought it new, it's highly likely that that's the way it's designed.
Assembly-line wirers don't make mistakes like that...
> i had a problem like that with my cruser, when i turned the tone down
> to bass it cut the sound out completely and wudn't play... the reason?
> the tone knob was earthed when it shouldn't be...someone did some
> dodgy wiring.tho its fixed now thanx to chris, oh yeh let me take this
> oppitunity to thank yu chris :) cheers!, ne way this may or may not be
> the problem im just throwing up ideas
IME, guitar tone controls is a funny old game. Most electrics have tone
controls which cut way more treble than you'd ever actually want to cut,
meaning that the sound with the control backed right off is more or less
unusable. There are exceptions, like my Guild Manhattan, which only removes
enough treble for an authentic "jazz guitar" tone, or like the two-switch
Gretsches (one of which is a very well-thought-out preset tone switch), but
by and large, tone controls usually have more sweep than the player really
needs or wants. In my view, it would be a mistake to expect a Really Useful
sound with the tone knob at zero or one.