A recap
- No sound through both spkrs, low hiss through spkrs & headphone
- relay clicks, approx 2mVdc at speaker posts
- Mic volume switch produces popping through the speakers
- no sound with operating the CR as either a PRE or power amp
- voltage/supplies 49v, -49v, 10v, 10v. -11v, 11v, -49v, -26v, -50v, 33v., -12v
Suggest, with CR powered off/unplugged
Set coupler switch set to OFF
measure resistance from Left MAIN-IN RCA (inside) to IN pin on left power amp board
measure resistance from Right MAIN-IN RCA (inside) to IN pin on right power amp board
Set coupler switch set to ON
measure resistance from Left PRE-OUT RCA (inside) to IN pin on left power amp board
measure resistance from Right PRE-OUT RCA (inside) to IN pin on right power amp board
In all cases expect maybe 1 ohm
Both pre/power/both channels affected, psu looks OK, that coupler switch can be a pita.