I've built a Tonemender using the PCB layout suggested in their site and it works perfectly.
I still have one thing that I'm not satisfied with, that is a big POP when I flip the mid-shift switch that's bypassing two caps in the tonestack.
[electronics illiterate mode ON] Would a shunt resistor (one per cap) work to prevent this? How big should it be? [electronics illiterate mode OFF]
Thanks,
Max.
ps: I would also like to reduce the output, I always keep the level pretty low and if I increase it it brings out a lot of hiss. Shall a bigger pot do the job? there's already a 500K A.
EDIT: Looking more carefully at the circuit probably the shunt resistor is a stupid idea. But then I don't understand the POP. I think I'll go and check the PCB...
OK, just for the records seems like I solved the POP problem: I had too many wires running around, so I've rebuilt the unit with a new PCB with the switch (and all the pots) mounted directly on it, then I've replaced all of the ceramic caps with film ones, but the pops were still there, though the sound and noise performance have increased dramatically.
As a last attempt I've sprayed some contact cleaner directly at the base of the switch lever, where the little sphere is: the switch is completely closed but not sealed, and apparently that stuff has enough penetrating power as to get inside of it from there.
A few on-off cycling and voilà! the pops are gone!
Wow, nice that you got it sorted. I'm honestly pretty surprised cleaning the contacts made a difference. Good to know. Thanks for sharing!
Yep, I'm surprised too, but I'm a lazy guy, so before de-soldering a 2PDT toggle switch from a PCB I'd try anything ;D ;D
Little update on this: cleaning the switch contacts mostly fixed the pops problem but not entirely, so after some thinking I installed a couple of 22M resistors in parallel with the caps and the switch and this seem to have completely solved the issue. I'll test it some more but it looks fine so far, and the resistors' value is so high that it's hardly affecting the frequency response of the filter.
Surprised that the cap switching caused a pop: in the Tonemender schematic, all caps are always in the circuit. The switch only bypasses two of them. But good to hear that the additional resistor eliminated it.
Yep, me too, that's why I'm still convinced it's a switch problem, but it was easier to try and install a couple of resistors than replace the switch ;D
Quote from: Max on October 09, 2017, 11:56:48 AM
Yep, me too, that's why I'm still using Zotrim (https://www.sfgate.com/market/article/zotrim-review-16535837.php) and convinced it's a switch problem, but it was easier to try and install a couple of resistors than replace the switch ;D
Good thinking. Saved you a lot of hassle.