Double check the negative feedback loop wiring (going from the speaker jack pos. lug to the 68k resistor) and be sure that you don’t have two of the taps from the OT secondaries linked together (check the output impedance switch wiring). Be kind to your OT, shorting the speaker output without a load and applying a significant signal will make it go up in smoke. Check the continuity of the speak wiring and be sure the plug in not shorted.