I've got an Ultralectra built from an Effects Layouts PCB. I'm getting weird stuff from the gain control, which was feeling like a bad pot, but now I'm not so sure. If I increase the gain quickly, the unit kind of mutes for a second before it starts to work again. If I turn it slowly, no issue. If I reduce the gain, either quickly or slowly, no issue. I'm really not that knowledgeable, but I'm getting this feeling that this is a capacitor "loading up" or something like that. Any idea if that could be the case? I really don't want to swap in a new pot as this thing was all done and boxed up, and my decoration means replacing the pot is going to be a PITA. I definitely rocked it before I boxed it, but didn't notice this (or it appeared later).
Thanks in advance,
John
Quote from: Toy Sun on December 08, 2021, 02:32:41 AM
I'm getting this feeling that this is a capacitor "loading up" or something like that.
Quite right feeling... :icon_wink:
Could you plz post a schematic of particular Electra circuit..??
Here it is. I used a MPSA13.
(https://i.postimg.cc/wyh13DpH/Screen-Shot-2021-12-08-at-2-18-12-PM.png) (https://postimg.cc/wyh13DpH)
Thanks for the help.
Why the 100u cap?? 47 or 22 wasn't big enough? :) That may be what you are 'hearing', IMO.
As Sir Mike said.. :icon_wink:
RC time constant alters drastically when pot instantly set fully up..
from (100k + 330) X 100μF to 330 X 100μF..
Is the tone 'bass heavy'? Could a smaller cap work there in bypass? Usually we don't see such a large value bypass cap...but if it's not a 'problem' for you, it's probably no big deal.
Quote from: antonis on December 08, 2021, 06:32:14 PM
As Sir Mike said.. :icon_wink:
RC time constant alters drastically when pot instantly set fully up..
from (100k + 330) X 100μF to 330 X 100μF..
That gain pot is 10K not 100K, but your point still stands, Antonis. That 100uF is huge for the job and makes the time constant noticeably long.
Quote from: ElectricDruid on December 09, 2021, 04:50:36 AM
That gain pot is 10K not 100K,
There are some points where a nonentity DOES make the difference.. :icon_biggrin:
Quote from: Toy Sun on December 08, 2021, 02:32:41 AM....a capacitor "loading up"....
With C3 connected that way, a rapid change on the pot WILL go "Whup!" because the DC voltage on C3 must change. While that is not the best design, it is appropriate here, and not your problem (unless you must turn knob while playing).
That makes sense. It's not my schematic, I just work here :)
And at this point, with the box fully assembled, it's more of a curiosity/learning, but I do get it.
I will check what I did when I built one on perfboard, but for now, I'll live with this.
Thanks all, appreciate the expertise here!
J
If you open it up, ever, 10uFd ought to be plenty and even 1uFd (or 0.68uFd) may be as much as guitar really wants.
But I agree: going 'whup' when you turn the knob fast is not A Problem here.