How long is long enough to test an amp after repair?

[spooney]

Just wondering what everybody considers a thorough test of an amplifier after repair. I don't do any work for people just work on my own stuff so after I repair them I try to run them in my car at their lowest rated ohm load for about a week. If I were to say just hook them up long enough to warm them up a bit(maybe 20 -30 minutes) at their lowest rated ohm load is that sufficient? Is that long enough for any problems that may still be lurking to pop up?

[0ldSch00lf00l]

On the last amplifier that I repaired for myself, I ran it hooked up to dummy loads with a 60 Hz tone until it went into thermal protect. Next, I let it cool down to see if it would power back up. It did.

Oddly, the person I purchased the amplifier from had abused it to the point where two resistors had melted out of the circuit board. I was trying to see if I could recreate that issue by pushing it into thermal, and I couldn't.

[Perry Babin]

If it runs at full power for 10 minutes, it's probably OK.

I generally run amps for several hours playing with music and driven into clipping about 10% of the time. This is with a dummy load at twice the lowest rated impedance. If the amp is rated for 2 ohms, I use a 4 ohm dummy load.

It's good to run to thermal but it's not possible to do it with class D amps. For class D amps, if you fail to find a defective component, the failures will come almost instantly after powering them up, even without a speaker load. For almost all class D amps, if you play them for an hour or more into a 4 ohm load up to clipping (intermittently, with music) and they don't fail, they are OK.