I've built a phase 45 and everything sounds great except for one thing. It's like the "manual" setting on an EHX Bad Stone has been switched on, the LFO seems like it's stationary instead of actually oscillating. The phase can be shifted using the bias trim pot, but I kind of need both my hands to play. Has anyone experienced something similar? Or can somebody point out where on the schematic the LFO is generated? I'm not experienced enough with electronics yet to visually identify the section.
The schematic for reference:
http://www.generalguitargadgets.com/pdf/ggg_p45_sc.pdf
Thanks a ton!
Quote from: universalmind81 on June 17, 2022, 09:41:39 AM
can somebody point out where on the schematic the LFO is generated?
IC2b and relevant circuitry..
(R20 to R24 and C9)
Thanks, I appreciate the info!
More strictly speaking, basic LFO consists of R20, C9, IC2b, R21 and R22..
Your issue might be due to op-amp out saturated on either supply rail or discontinuity between R24/R27/R25/C10/GND/R23/R25..
Could you take a measurement on pin7/R22/R24 joint..??
In case of getting a fluctuating signal, check continuity path as below:
(https://i.imgur.com/trYRSUr.png)
That was it! There was a tiny break in the trace between R24 & R27. I spend so much time looking for solder bridges and unintentional trace links I don't know how I missed the break. Been staring at the damned thing too long and went blind I guess lol. Thank you for narrowing the problem area down, that's been bothering me for weeks!