Yes, you should first do the offset tests at the speaker terminals, no sound, just turn the volume all the way down.
It sounds to me like the next thing to check is the base drive signal for the relay driver transistor. The transistor is being told to keep powered on continuously but is falling down on the job.
BUT the important part of the answer is still missing:
so I must explain:
The click and no sound:
when it clicks and there is NO sound
if the sound is MISSING for the five to seven second delay
or if it comes back FASTER.
Five to Seven seconds means the protect integrated circuit is UNHAPPY with an input and is TELLING the relay to disengage ON PURPOSE
This for example could be excessive DC offset...
a faster return of sound indicates the relay driver transistor (q2, 2sc1438) is falling down on the job. DC offset could be ok.
The base lead of Q2 on the awm-124 protection board can be tricky to get to, with danger of shorting other things nearby. The awm-124 protection board is tucked into the bottom of the chassis.
It's best you download the same
(32meg) service manual I am using so we are literally on the same page.
Page 20 shows where the awm-124 protection board is
Page 58 shows the board layout FROM THE BOTTOM!!! You will be looking at it from the top, a mirror image...
See the words "foil side" at the top of the drawing?
Q2 is right next to that. It has THREE connections. Two are parallel with the edge of the board, and a third is further in towards the center of the board.
This third connection/lead is the one to measure.
BUT it is done with the POWER ON (careful!!) and the music playing.
The black DMM wire/probe goes to the bare metal chassis somewhere (ground)
The red DMM wire/probe is what you measure around with.
INSULATE ALL BUT THE TINIEST PORTION OF THE TIP OF THE PROBE WITH TAPE, so that when the probe slips (We ALL slip!! when we move our eyes to read the meter) no harm is done.
The reading should be in the range of 0.7 volts (0.6 TO 0.8) when the relay is supposed to be on, and about 0.000 volts (well less than 0.1 volts) when the relay is supposed to be off.
If the 0.7v stays when the relay clicks out, we have our culprit, q2
If the 0.7v goes away when the relay clicks out, then the problem lies further up the line...
To access the underside - stand the chassis on it's side with the bottom off, and it's best if the heavy power transformer is closer to the table top.