Voltage regulators take a higher voltage and regulate it to a lower voltage....so when you say you have 90 volts on the input and output and expect it to regulate the output to 123 volts doesn't sound right. That is, if I understand what you are saying. The input should be much higher coming from a 120 volt A/C through a bridge circuit, I would expect to find something closer to 160 volts passing into a series of resistors until I had a working voltage usuable by the regulator. I'd expect a bad resistor or cap leading to the regulator.