But, since we know that R45 is a 33ohm 0.5W resistor we can conclude that if we pass more than 123mA through it we'll exceed it's power rating.
Oh yes I see: √(0.5W÷33Ω) = 0.1231A Or 123mA
So if you have a small bench power supply with current limiting...
Unfortunately I do not have a power supply with current limiting (it is on my list to get one). Only an old ATX PC power supply I converted into a very basic variable voltage power supply.
I just received my new 33Ω 0.5W Metal Film Resistors today!
I don't mind sacrificing one or two resistors, they cost pennies. Hopefully nothing else blows up in the meantime though.
So I replaced R45 (and also R46 because I sacrificed R46 in R45's place earlier and it is in resistor heaven) with brand new parts.
I measured the voltage across the resistors in standby, protection mode (for a few seconds at power on) and also at power on state.
As you can R45 (on the +18V rail) is indeed drawing more than it's power rating by quite a bit, but only after the protection turns off.
Although it does appear to be drawing a bit too much current for my liking even in protection mode!
R45 = 32.97ΩSTANDBY 0.00V (0mA / 0mW)
PROTECT 3.76V (114mA / 432mW)
ON 5.23V (158mA / 826mW)
Although R46 (on the -18V rail) is looking good to me.
R46 = 32.78 ΩSTANDBY 0.10V (3mA / 0.3mW)
PROTECT 2.90V (89mA / 258mW)
ON 2.91V (89mA / 259mW)
The good news is that with the two resistors in circuit I have no DC on the speaker outputs and the protect mode does indeed switch off when it is supposed to.
There are a few resistors that you can measure the voltage across to figure out how much current is going through them: R254, R154, R616, R615
I will check these next and see what the current is.