-2V around u10 p7...we replaced zeners and R39 (again) but they did not help. Checked CV circuit upstream with 5v triangles into CV1 CV2 sockets and saw correct frequency with Cv2 pot centered. This suggested U10 okWhat's your lowest voltage on pin 7 U10 (delay pot at min and trimmer down as low as it can go)? It should be around -6.5V. If not that negative then check circuitry around U10..
as are resistors including r34 from delay pot which works.
We were curious how moving CV2 pot can change frequency (and get closer to -6v without CV2 and CV1 having anything plugged in ?
If it shouldnt, the we suspect one half of U17 might be injecting a voltage.
It appears pin1 of U17 has between 13.8 and 14.2Volts depending on the position of CV2 pot . Is this ok ?
I need a few days for replacement tl072s to be delivered before i can replace.
Ok retried with no input, drive minimum, fbk maximum I get to 9am position and it oscillates with feedback. The trimmer only has an effect if i back off Drive to say 12 pm. Im rechecking BBD signal ins and outs.. I have a 142Hz in and a 19.2Khz out - all pots minimum.With the FBK trim we are looking to set the maximum amount of feedback. We're not really looking at distortion but the level of self-oscillation. There should be no input signal used in this part of the calibration.
yes ..proved by accidentally shorting pin7 to pin8 ..both light up. Pin5 has no voltage. The voltage from the signal appears at U11 pin1 and p2 D14 but not p1 D14 . Ill be replacing this next. EDIT Replaced D14 and I now have 6.x volts on pin5, 1.2V on pin 1 U13. Both LEDs alight.Have you checked that the LEDs are the right way around? Check the voltage at pin 5 of U13. You should see a positive voltage at this point when you have a signal present at the input of the module. The voltage should be proportional to the signal level.
..Now how do I turn the red one off .. I reduce frequency of input signal to lfo level and still both. Removing input completely works. It seems a 4.x V signal at U11 pin1 is now uplifted to 6.x V signal appearing at p2 of new D14 If cv2 pot is centrered and i move freq pot from minimum i can find a tiny sweetspot where red goes off...so external cause assumed for now.
enjoy rest of bank holiday.