Boss RC-20XL No Signal No Output Repair Notes

[fixy88]

Placing this here to help others with this repair of the Boss RC-20XL guitar loop pedal.

Symptoms: No signal or very faint signal on both INST and MIC inputs.

Cause: OPAMP IC12 blown. VCC/2 at 5.2v when it should be at ~4.2v.

Replaced IC12 with a 4580 and unit functions as it should.