Prophet 5 3.2 dead voice not CEM related
2013-08-02 by cxacxu
I've got a troublesome P5 rev3.2 here that has a dead voice no. 4 vco B, vco A is ok. The CEM is not the problem, I've traced back through the S/H circuit I can see there is no signal on the 4051 U406-4 which should be the S/H for that voice, changing both 4051's U405 & U406 did not help nor did changing the opamp U404. Also voice 3 vco A is in tune, vco B is out of tune when autotune completes, calibrating vco B goes back to being out of tune once rebooted and autotune completes, I've changed both 4051 U439, U440 tuning demux ic's. I'm wondering if both problems are related but could do with some advice. thanks Luke