Help, behringer amp module from PMX660m

[chipprogr]

I need some help please. I am repairing the amp module from a behringer box mixer/amp model PMX660M . One of the IRF640n fets went out and has been replaced along with one of the 0.1 ohm resistors. Thats all i can see wrong. I fire up the amp and the relay on the output jacks wont engage. There is audio there and the amp works now, but wont ground the relay to connect amps to the speaker jacks. The crowbar circuit on the output jacks ( triac based crowbar) is fine. There is a black/red pair coming off the amp module that heads down to the power supply. THere is +15vdc on the red, black is gnd. Then there is another black red pair from the power supply (same area of the PCB) that heads out to the relay on the output board. There is 14-15 volts present on both. I expect that one of them needs to ground to activate the relay, but what circuit board has this function of the relay control- amp or PSU?

Thanks for the help -Eric