UPDATE:
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Changing R17 to 22k instead of 10k fixed it. May have been an issue with the OPAMP bias in the SA571 using the original 10k.
Original Post:
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Hi, I built the Echo Royal recently and I noticed the output is clipping on the distortion signal. If I go 100% wet its definitely coming from the delay circuit.
I got my signal generator/oscilloscope out and traced the issue down on the schematic.
The signal coming from the "Delay out" going into the SA571 at pin 2/3 is fine, but the signal going out of it at pins 6 and 7 has the top half of the waveform clipped.
Attachment:
File comment: Section of Schematic
schem.PNG [ 18.47 KiB | Viewed 738 times ]
Attachment:
File comment: Waveform Example
waveform.png [ 19.46 KiB | Viewed 738 times ]
Any ideas of what to check? I did replace the 1uf at C16 and the 100 pf at C17 to rule out the parts there
Pin 5 seems to have a square wave of some sort on it (Inverter in on IC) but Im not sure if that is correct?
As a troubleshooting step I also removed the capacitor after pin 6/7 to check if the issue was coming from farther down in the circuit but the issue persists even with that removed so the issue is coming directly off the IC.
I also checked the voltage on the chip and its -1.8v which seems to be what the chip should be getting.
Other than the distortion everything else on the pedal is working as expected.Based on online demos this seems to be unique to my unit.
Could half of the SA571 not be functioning?
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