The protection board readings you posted look fine.
The board needs to be rebuilt. Q1 and Q2 are suspect.
This is the current rebuild list for the protection board:
Protection Assembly (AWM-025)
AWM-062-0: C1: .22uF 10v CSSA: 505-MKS20.22/63/5 .22uF 63v
AWM-062-0: C2: .22uF 10v CSSA: 505-MKS20.22/63/5 .22uF 63v
AWM-062-0: C3: 330uF 6.3v CEA: 647-UPW1A331MPD 330uF 10v
AWM-062-0: C4: 330uF 6.3v CEA: 647-UPW1A331MPD 330uF 10v
AWM-062-0: C5: 4.7uF 25v CEA: 647-UPW1V4R7MDD 4.7uF 35v
AWM-062-0: C6: 100uF 16v CEA: 647-UPW1E101MED 100uF 25v
Q1: 2SC869: 512-KSC1845FTA
Q2: 2SC869: 512-KSC1845FTA
Q6: 2SC945: 512-KSC2383YTA
Q7: 2SC1384: 512-KSC2690AYS
1N4004 flyback diode is added between pins 9 (anode +) and 10 (cathode -)
This is the troubleshooting procedure I use for checking the protection boards.
Courtesy Mark aka "MTF".
Backwards troubleshooting procedure:
Remove q6 and q5 , power up unit, relay should click after time delay.
Install q6, relay should still click after time delay, also now when fuse supplying 7.5v ac to pin 12 is pulled, relay should click out, and when fuse reinstalled, wait time delay and click in.
Before installing q5, lift the cathodes of d5, d6 and d7, then install q5.
It should continue to operate as per q6 step above.
While the relay is pulled in, ground d5 cathode momentarily (150k ohm R18 does good job current limiting - so no danger) and see that relay "protects / releases" with time delay before reengagement. do the same for d6 and then again for d7
Now reinstall d5, this is the overcurrent "input" for the protect. The relay should still pull in - as we have no audio going out and no speakers connected.
If the relay does not pull in, we need to look at (just plain replace) the two over current sensing transistors, one per channel and in some cases maybe on the amplifier card.
Reinstall d6 and d7 as a pair. this is the DC detect circuit. The relay should still pull in - as we have no audio going out and no speakers connected.
If not ok, (and pins 1 & 3 don't have over 50 mV on either of them) we need to lift R9 and R10 's pin 1 & 3 ends, and ground the hanging in the air leads to see if the dc detect circuit is behaving.
One last thing:
I'll remove the jumpers when securing the amps and protection boards. It removes the influence of the unrestored pre amp which has some troublesome transistors in it. If you haven't worked the pre-amp it's a good idea to have the two amps separated for the time being.