How to burn in or test a repaired amp?.

[jeffn]

I've taken back a returned amp I sold on ebay because it "fired up" when used.

I found 2 dead output transistors, and a fired up resistor.

Before sending it back I want to give it a test that won't wake the neighbours.

Is there a recommended way to do this?

[markthefixer]

Reliable load resistors... that can easily handle the wattage....

I also am interested in how some of the others here "torture test" things....

I thought I had run homer's 150 watt subwoofer plate amp through the mill at full power for over an hour before I shipped it back, yet he managed to quickly pop it, and I'M waiting to open it up and see what happened...

Yet other amps have yet to give problems.... I used ON-Semi's on THOSE....

[markthefixer]

bump

[justw]

After half an hour warm up check and adjust bias and balance as needed. Connect appropriate wattage 8Ω resistors across speaker terminals. Monitor with a scope and ac voltmeter while applying 1kHz sine wave to an input. Turn up the volume untill clipping on either channel and back it down to just below clipping. Calculate the power output, E^2 RMS / R, and compare to spec. All the while keep checking the heatsinks for excessive temperature. Turn down the power to 66% of rated power and let it run for an hour. If it plays fine and doesn't melt down it should be fine. However, there are many things that can go intermittant on a power amp that can cause you grief. But, an hour burn in is a pretty good indication of it's health.

[ak_47_boy]

I use two nails stuck in a salt water solution. Works great for five minutes at 200watts of testing. Big wirewound resistors are expensive. I have had one overheat and short also :( It takes a little fiddling to get the right independence tho.

[sleddogman]

I use two nails stuck in a salt water solution. Works great for five minutes at 200watts of testing. Big wirewound resistors are expensive. I have had one overheat and short also :( It takes a little fiddling to get the right independence tho.
Photo please...?

[jeffn]

I use two nails stuck in a salt water solution. Works great for five minutes at 200watts of testing. Big wirewound resistors are expensive. I have had one overheat and short also :( It takes a little fiddling to get the right independence tho.

I can't believe I'm asking this but............... how much salt??

[sleddogman]

LoL! That was going to be my next question if he didn't include the ratio with the photo, so I'm glad you asked first... :pawprint:

[LBPete]

Salt to taste?

- Pete

[jrsh92]

Add salt until it comes down to 8 ohms. Absolutely pure non-salted water is not conductive to electricity

[markthefixer]

Sounds yummy..... I used to work at a place that made hydrogen generators... put water in, get hydrogen at one electrode and oxygen at the other... salt was the ultimate poison for the system.

And of course we're feeding in AC... Hydrogen and oxygen at the same electrode....

At least the hydrogen heads straight for the ceiling....

But the salt is NaCl..Sodium Chloride... and in water it separates into sodium ions and chlorine ions.

Hydrogen and Chlorine is HCL... because the hydrogen is small bubbles in the ionic salt solution.

But this also liberates chlorine gas....The gas bubbles are a greenish-yellow color.

So here you are, with hydrogen gas, oxygen gas and chlorine gas, and if it builds up in an enclosed area, you are going to get a TREMENDOUS BASE Pulse.... it'll probably take out your windows... it's called an explosion...
At those wattage levels, that's a LOT of gas...

Hmmm....
1913
The Electro-Alkaline Co. was formed in Oakland, Calif., to make sodium hypochlorite bleach, derived from chlorinating a solution of caustic soda, a process developed a century earlier. The active ingredient of most household bleach today, this was costly to make until the early 20th century, when cheaper electricity permitted electrolyzing salt brine from salt ponds.

This is just the anode (which switches on every half cycle of ac)
1) 2Cl- -----> Cl2(g) + 2e-
or
2) 2H2O ------> O2(g) + 4H+ + 4e-