I built the E. Nigma from Dead End FX, which was a fun, huge, challenging build. Right away it passed audio but when I was biasing the daughter board (the BBD), I didn't get any flange at first. Once I turned down the rate and manual knobs I started to hear flange and could basically follow the biasing instructions.
However, the LFO is just way too fast. Even with the Rate knob all the way down, it's still going at about 8-10 Hz. I can get a garbled Leslie effect but not much else, certainly not the classic slow sweep flange effect. The LED/LDR combo on the daughter board seems to work great, if I wave my hand over it with the lights on I can force a nice slow flange and it sounds nice. But turn the lights down and I see the LED beating really fast with the LFO.
I also get no audible effect from turning the Regen bias pot on the main board...it's supposed to set the self-oscillation threshold but I can't make anything happen. Turning the React knob seems to do nothing. Tremolo seems to work fine but again, the LFO is way too fast.
Any ideas what's going on or where to start? Here is a link to the build document:
https://drive.google.com/file/d/1kqEvRodTRtgS7zFl3puy6qp6RXRRoSle/view
Although, 8 - 10 Hz (125 - 100 msec) shouldn't be considered "fast" (IMHO), you can tweak R63/R68 values..
Thank you, I'll check my values. Most flangers can do a very slow sweep, something like 0.1 Hz, and from youtube videos the Lovetone is similar. That's why I say "fast"
Turns out I had 100k in R68, not 100R! That fixed the LFO, now it's exactly what I was expecting in terms of speed. Checked all the other resistors too and they are correct.
However I'm still not getting regeneration from the Reaction knob. I've started checking continuity.
A general question: should the emitter leg of a transistor ALWAYS show voltage? Because a few of the BC549C read 0v from the emitter. They are NOS transistors (BC549C is no longer made) so I wonder if I may have some duds. I don't have transistor testing on my DMM or else I'd test them.
Quote from: slowpogo on March 09, 2020, 11:22:28 PM
Turns out I had 100k in R68, not 100R!
You're now able to calculate Rate difference for various R68 values.. :icon_wink:
Quote from: slowpogo on March 09, 2020, 11:22:28 PM
A general question: should the emitter leg of a transistor ALWAYS show voltage? Because a few of the BC549C read 0v from the emitter. They are NOS transistors (BC549C is no longer made) so I wonder if I may have some duds. I don't have transistor testing on my DMM or else I'd test them.
I'm a little confused with your query.. :o
Transistors Emitters show nothing by their owns - as any other circuit point.. :icon_wink:
In you mean voltage difference, e.g. between Emitter & GND, it depends on particular circuitry..
In case of testing them out of circuitry, DMM diode setting should be OK..
i.e. B-E ON E-B OFF, B-C ON C-B OFF etc...
Thanks for your response above, and I apologize for the weird question...it's obvious that I build pedals but don't have much EE knowledge. I couldn't work on this for a while, but finally got back to it. Turns out I had a few bad transistors, I replaced them and the pedal is basically functioning as it should! Hooray.
The only issue is clock noise at the upper end of the Manual and Depth knobs. It goes away if the pedal (which is now boxed) is away from the bottom plate, or the floor. Being in proximity to something (even just carpet) seems to bring on the clock noise. I did use a shielded wire as instructed. Contrary to the setup instructions, adjusting the BBD bias does not make the clock noise go away.
Truthfully things get *really* weird with those settings anyway and I'm not super likely to use them, but I would like to figure out how to make the pedal clean regardless.