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Ineffective tone control - passive bass


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#1 Grangur

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Posted 16 January 2017 - 09:34 PM

Hi all, this last weekend I picked up a new project. It's an Ibanez EXseries.

It's a PJ with passive circuit. The jack doesn't work and the pots were in poor shape. When working the tone control it didn't seem to do much. "No matter", says I. "It'll be okay when I've changed the circuit."

Fast forward to tonight. I've changed the 3 pots in the VVT circuit including using a new orange capacitor. Plug it in with a temporary jack, as I won't have the long reach jack until tomorrow. All is well with the VV, but the T hardly does anything.

All the pots are 250k ohm. The tone is wired with the in/out connected to one of the outside lugs and the capacitor goes from the centre lug to ground.

There's an earth connection soldered across each of the cases of the pots. Another earth goes from the cases to the bridge and one to the jack sleeve connection.

Anyone here got any ideas? Has anyone have this happen before? I can only put it down to the pups. They're okay, nothing special. So far I don't think its a keeper. I just like doing up basses.
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#2 MoonBassAlpha

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Posted 16 January 2017 - 09:50 PM

The cap could be duff. Do you have any way of measuring it? Many multimeters have capacitance measuring function.
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#3 Grangur

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Posted 16 January 2017 - 10:33 PM

 MoonBassAlpha, on 16 January 2017 - 09:50 PM, said:

The cap could be duff. Do you have any way of measuring it? Many multimeters have capacitance measuring function.
Could be. But the chances of both capacitors; the original and the replacement, both being duff is remote. But I think I'll still change it when I put the jack socket in tomorrow. I've got some spares, so nothing to lose.
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#4 timhiggins

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Posted 16 January 2017 - 10:45 PM

This may sound silly but are they really old dead strings as i have had bass's where the tone control seemed to do next to nothing until i changed strings and then they come alive !

#5 Woodinblack

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Posted 17 January 2017 - 12:02 AM

When you say 'hardly different' is that slightly different or not at all?

I would try it on a different amplifier with a higher impedance input, and check that the input didn't have an active input option.
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#6 Grangur

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Posted 17 January 2017 - 06:29 AM

 timhiggins, on 16 January 2017 - 10:45 PM, said:

This may sound silly but are they really old dead strings as i have had bass's where the tone control seemed to do next to nothing until i changed strings and then they come alive !
The strings are new. I can see your point though.

The control makes little or no difference.
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#7 Grangur

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Posted 17 January 2017 - 06:31 AM

 Woodinblack, on 17 January 2017 - 12:02 AM, said:

When you say 'hardly different' is that slightly different or not at all?

I would try it on a different amplifier with a higher impedance input, and check that the input didn't have an active input option.
If it makes any difference I don't think I can hear it. I tried 2 amps. Can't say I tried the active/passive switch though. I do that later.
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#8 MoonBassAlpha

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Posted 17 January 2017 - 07:37 AM

All very odd. The chances of 2 duff pots is slim, but not impossible...
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#9 Woodinblack

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Posted 17 January 2017 - 11:28 AM

Short the two lugs of the tone control with a piece of wire or whatever, so the in / out is connected directly to the cap. If it makes no difference the cap is dead or not connected, if it does the pot is dead or not connected
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#10 Grangur

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Posted 17 January 2017 - 02:36 PM

Many thanks guys.

I changed the cap with another new one and all is now well in the world. It's got nice tone now. There's actually a danger of me liking its tone more than my Fender!
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