Hello,
I just build two MU524. The first one is working and I had no problems with calibrating the unit . 
But the second one has over 26Vac at the Output in Step 6, were it only should have 3-4Vac. In Bypass it is the normal 1Vac at the Output. As soon as I engage the the bypass to „In“ its 26V. I checked the pots and could‘t find and mistakes. Do you have and thoughts? 

V+ and V- are +- 15-16V 
B+ is 46V
TP1 = 30V
TP2 = 27V but maybe its because I didn’t end the calibration. 

Best regards! 
Benjamin