Optonica 5406 receiver in protection mode.

I just got an Optonica SA 5406 receiver that goes straight into protection mode. Protection LED is amber and you cannot hear relay click. The tuner works OK though and it pulls in stations but no output - even on headphones.
I am pretty inexperienced when it comes to circuit repair but I bought this in order to learn. I have previously re-capped a Marantz 2250b but diagnosis and repair is at the limits of my knowledge so bear with me.
I have a copy of the service manual which I got from stereomanuals.com (good service, by the way!) so I have the circuit diagrams and I have a DVM, soldering iron and access to an oscilloscope.
There are no obvious components burnt out and the fuses are OK. Tracing the power from the power supply it enters a pre-driver amplifier that is based on an STK3082 integrated circuit so I figure this is a good place to start as it affect both channels so I figure it is probably at a part that is common to both channels.
My question is, how do I diagnose what is going on in this circuit and whether it is working or not? Here is a pic of the circuit.

I could be wrong but I do believe the protection would cut all of the channels' outputs even if the fault was only on one channel, so it's not necessarily a fault common to both.

best to look at the voltages of the outputs before the relay ..ideally 0v .. but a few mv ok . and expected .
first try without anything connected to rule those out . see if relay clicks .

Next step will be to set the bias and DC offset.

The optonicas are gorgeous.

I'm not seeing steady readings on either channel. Left goes between -50mV and 60mV over 30 sec and right 0mv then cycles up to 60mV in similar time. Re-check of left then shows 100 -120 mV.

In the manual it says to adjust a variable resister to set the neutral point to 0v. The left channel I can get very close to 0v but the right stays rock steady at 47v, no matter how I adjust the VR.

I realize this thread is over a year old, but I am now having the same issue with a 5406 as well...

bluehills5, I am curious if you ever figured yours out (not that mine will have the same issue but it would give me a place to start). I was also wondering if you might be able to share your manual? I only have a manual for a 5606 which can give me some information but not much. Thanks!