Like Joe says, "yep, it means something" but not ready to say it's the DCP itself. Are you watching the DC level on the outputs as you bring up more and more voltage? From memory (forgive me Joe lol) I would say that with around 30 volts on the rails, the outputs should be zero'd out by then. If both channels are good and stable by 50 volts or so and the relay still hasn't kicked in, then yeah.. something's up with the DCP perhaps..
Finally catching up on stuff around here and am going back to the 400 to try some of the tests sent to me here... one question I had the was never answered was about step 8 in the DCP manual...
"8. If a signal generator is available insert a 1KHZ sine wave into the left channel. Set the
generator level to obtain 40 VAC on the amplifier output."
I do not have a signal generator that can apply voltage all I have an app to run out of my laptop. Would it be the same if I just put 40V to the amp with a variac then apply 1Khz from my laptop to get same results?
On JB's test
Left channel - I bring up voltage watching DC on the outputs at 30V .003mv dc at outputs it stays at .003mv at 50V no relay kick in... relay kicks in at 75V AC, DC on output goes to .138mv then .121mv DC at output at 115V AC from the variac
Right channel - at 30V .008mv at output at 50V no change still .008mv still no relay kick in 75V relay kicks in .135mv DC at output then .115mv DC at outputs with 115V fed in from variac