Simplified Eldred Mod question

[thaynes]

I have just wired up my Esquire using the Fralin simple diagram. The tone cap for the blended is an orange drop and the for the cocked wah is polypropylene film cap. The cocked wah tone cap is 100V and 4.7nF. My problem is switching to position 3 (cocked wah) produces an audible pop through the amp. Switching any other positions is completely silent as expected. Also, in position 3 there is a hum from the guitar that goes away when I touch the strings. Other positions are quiet. There is a ground wire soldered between the bridge plate and the volume pot.

Any ideas on debugging these issues would be greatly appreciated.


thanks,

Tom

 

[SnidelyWhiplash]

Pics of your work would be most helpful.

 

[thaynes]

Pics of your work would be most helpful.

Without desoldering, these are the best that I can do. I am not sure how helpful these will be.

Further testing, when switching into position 3 and touching the strings, the pop is greatly reduced.

Thanks for your help!!

Pics of your work would be most helpful.

 

[----RIP----]

Maybe it's static charge build up--producing a voltage---on the 4.7nF wah cap. Try a 10Meg resistor in parallel with it to discharge the static.

The 4.7nF wah cap is over 10x smaller than the 50nF normal tone cap. Because V=Q/C, a static charge, Q, will produce a 10x higher voltage on a cap that is 10x smaller.

 

[thaynes]

Yes! The 1M resistor in series with the wah tone cap eliminates the popping noise when switching to position 3 and greatly reduces the background noise to the point where it is not an issue.

Thanks for the suggestion @----RIP---- !


Tom.

 

[Cal45m]

That pop in position 3 could be a DC leakage issue, try swapping the cocked wah cap for another type or lower voltage rating. The hum sounds like a grounding issue specific to that switch position, double-check all grounds, especially around the switch and tone cap.

 

[----RIP----]

Yes! The 1M resistor in series with the wah tone cap eliminates the popping noise when switching to position 3 and greatly reduces the background noise to the point where it is not an issue.

Thanks for the suggestion @----RIP---- !


Tom.

I'm glad it worked out!

But I had suggested a 10Meg in parallel, not a 1Meg in series with the wah cap. Which mod did you actually use? Is the cocked wah sound any different between having the resistor and not having it?

 

[thaynes]

I'm glad it worked out!

But I had suggested a 10Meg in parallel, not a 1Meg in series with the wah cap. Which mod did you actually use? Is the cocked wah sound any different between having the resistor and not having it?

had a brain fart... I did 1meg in parallel as I had that resistor on hand.

I have not spent enough time with it to determine if the sound is any different. I just put this esquire together, so still in the experimental stage. Position 1 has more treble than position 3, which is expected. I know if I change the tone cap, it will send more or less treble to ground.

@Cal45m - I did test continuity around the switch in all positions. The tone cap is connected to the back of the volume pot, as is the ground wire. I suppose it could be a bad switch.


Thanks,

Tom.