Clapton is woofing!

stratotato · June 2023

Hello! This is my first post actually. I have a 1989 Clapton Strat with the mid boost and TBX (which is actually quite pony really) and Lace Sensors. Recently the volume knob started making this incredibly loud whine/whoof sound on 6-8 on the volume knob.

I replaced the pot with a Bourns 250k logarithmic which was fine at first, and then does the same thing. 0-5, 7-8 WHIIINE, 10 absolutely fine again. It has a new battery installed and everything else seemed fine when I opened it up.

Any clue? thanks!

FelineGuitars · June 2023

Doesn't the Clapton circuit have a 50k volume , and not a conventional 250k?

CasperCaster · June 2023

FelineGuitars said:

Doesn't the Clapton circuit have a 50k volume , and not a conventional 250k?

Yep, volume should be a 50K log pot on the Clapton Strat as output comes after the preamp.

stratotato · June 2023

Well that would explain it then, though bizarrely it did it on the previous pot too but only after ~10 years of it being fine. I'll change it out and try again, if that doesn't fix it it's really at the end of my wiring knowledge. Or I'll just work out how to incorporate a high pitch, slightly sharp A into all of our songs.

thanks both for the help!

ryanverbena · June 2023

I thought this was going to be a post about him expressing political views!

ICBM · June 2023

If it’s something that’s developed recently it could be an electrolytic cap in the preamp failing - this is around the life expectancy of them. Why replacing the pot temporarily fixed it I don’t know...

Another possibility is a loose or corroded ground connection somewhere, it’s possible that changing the pot disturbed it and that’s why it stopped for a while.

As already said the correct pot value is 50K, so I would put the original one back at least for now, as it’s probably not the cause.

prowla · June 2023

ryanverbena said:

I thought this was going to be a post about him expressing political views!

I thought maybe he needed a bath!

prowla · June 2023

Generally 250k/500k pots are appropriate for passive circuits but active ones may use other values as they're controlling the circuit rather than working directly on the audio signal.

ICBM · June 2023

prowla said:

Generally 250k/500k pots are appropriate for passive circuits but active ones may use other values as they're controlling the circuit rather than working directly on the audio signal.

With this one it’s working directly on the audio signal, but as part of a buffered preamp so it needs to be a lower resistance. A normal high resistance one will work, but negates the benefit of the buffer since turning it down then introduces too much resistance in series.

Jalapeno · June 2023

ICBM said:

prowla said:

Generally 250k/500k pots are appropriate for passive circuits but active ones may use other values as they're controlling the circuit rather than working directly on the audio signal.

With this one it’s working directly on the audio signal, but as part of a buffered preamp so it needs to be a lower resistance. A normal high resistance one will work, but negates the benefit of the buffer since turning it down then introduces too much resistance in series.

TBX circuit is passive anyway isn't it ?

ICBM · June 2023

Jalapeno said:

TBX circuit is passive anyway isn't it ?

Yes, but only works properly with a buffer - otherwise it strangles the tone. Which is why it’s so baffling that Fender put it in all the USA Standards…

The 82K load resistor is far too low a value for passive pickups.

stratotato · June 2023

ICBM said:

If it’s something that’s developed recently it could be an electrolytic cap in the preamp failing - this is around the life expectancy of them. Why replacing the pot temporarily fixed it I don’t know...

Another possibility is a loose or corroded ground connection somewhere, it’s possible that changing the pot disturbed it and that’s why it stopped for a while.

As already said the correct pot value is 50K, so I would put the original one back at least for now, as it’s probably not the cause.

Ah ok, yeah its definitely beyond my soldering skills to start replacing anything on the PCB so I'll have to take it to have a tech look over, though there is every chance my wiring is a bit hooky, being the first time I've changed a pot in about 16 years.

Also managed to install push push on another strat, where phenomenally the push push does nothing, so I think it's fair to say I'm a bit of a wiring genius.

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Clapton is woofing!

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