Failure occurs when +B voltages up to 125V down to 120V and unstable. Hand-bound tube Q708 temperature normal, shows that +B load circuits were normal. Then disconnect the L971, C954 ends a 100W light bulb a false load trial bulb light, accompanied by flickering, indicating fault in switching power supply circuit. Multimeter to check the voltage regulator control circuit R955, R956, R903 and R969 were normal, program state measure Q951e voltage of 7V, VD971 works fine. Test Q951c voltage is 60V and unstable (normal values should be 64V). Remove Q951 check finds its beta value gets smaller. Replace Q951, after you recover the original commissioning, troubleshooting.