Quote Originally Posted by Light Dependant Resistor View Post
How wrong you are, 0v in the Crown iC150 is not zero volts as stated, as 0v is always in series
with C40. Connect 2 capacitors in series you get voltage at their junction... no mystery to that.

C40 is on the schematic is a capacitive connection to chassis ground,
hence a zero volt reference up to the currents involved with a preamp.

Crown's mistake was to take the floating ground concept a bit too far by relying on capacitors
alone. Two diodes should retain Crowns concept and allow connection at a semiconductor junction
at the same time, allowing residual voltages to properly dissipate.

Cheers / Chris
0 volts is whatever you choose as the reference voltage - there's nothing absolute about it. All voltages are measured with respect to something else, ie a voltage difference between two points is what is measured. It might be useful to the OP and to anyone who cares to contribute to this thread to establish what is being used as the reference point for voltage measurements. I suggest the negative side of the power supply should be taken as 0V, and that should be the same voltage as the negative end of R17 and the negative end of R20 and the negative side of C17 etc.
The design of this pre-amp is not really the issue here, it's how to rectify the fault so the pre-amp functions as it did when new.