You can
pick up a few of
these resistors and simulate a
speaker load, then
play pink noise or a drum kit
track to drive the
amplifier. A
pink noise signal is better for testing continuous loading, but a drum kit
track is ideal for testing program material where you have more peaks with a lower continuous
level. I would stay away from a 1kHz tone -- while commonly used for testing, it is representative of the worst case condition for loading an
amplifier and can misrepresent potential thermal issues, making a perfectly healthy
amplifier look like an easy bake oven.
I've also heard the heating coils for water heaters are a low
impedance, higher wattage load. That's a little more complicated to set up though because you need to mount the coils inside a metal trash can and fill it with water to keep the coils from burning up. The end result is something that looks suspiciously like a bomb -- a trash can, heated up, with wires sticking out of it.
The resistors are probably the easiest way to go for you in terms of simulating a load.
It may not be worth anything to test them outside of the rack. If they aren't getting enough airflow through your
amplifier rack and you test them while they're removed, your test may
reveal that the amplifiers are okay, but they may still give you headaches when you
drop them back into the rack with the others and your cooling issue presents again.
I would also look at the
manual and see all of the other possible causes for going into protect mode. If the
amplifier doesn't support a 2-ohm load but that's what you've got after 3-4 speakers have been daisy-chained together on a
channel, that may also present as a Protect Mode failure. I'm sure there are other potential causes listed in the
manual as well.
Other thing to look for is if there's any dust that's clogged the filters or the internals of the
amplifier. A thick layer of dust would cause thermal issues, and would be a better explanation for multiple amplifiers presenting issues at the same time than say manufacturer defect or old age.
