Power Acoustik A2400db

[timwebb]

i have this amp and one resistor keeps burning up. anyone repaired this amp?
the resistor at the bottom left.

[Perry Babin]

Is the Zener next to it shorted?

[timwebb]

the diode check tested fine. do i need to test it powered up?

[Perry Babin]

Is the resistor opening or is it simply becoming darkened?

If it's opening, how long does it take?

[timwebb]

it opens as soon as the light turn green.

[Perry Babin]

There's no need to have the resistor intact for this test.

With the amp off, find the end of that resistor that is directly connected to the negative speaker terminal. Place your black probe on that terminal of the resistor. Power up the amp and when the LED goes green, place the red probe on the other terminal of the resistor. What is the DC voltage? Polarity (positive/negative is important).

[timwebb]

ok i found the problem the guy who worked on it before used the wrong resistor.now i got one output transistor that puts the amp in protect.

[Perry Babin]

I'd replace Q124 and Q125 on the driver board with MPSW42s. Stand them off of the board near the fan blades of the cooling fan.

Also make sure that the cooling fan is running smoothly, with no vibration.

You'll need to replace all of the outputs if one failed. Don't buy them from eBay. I've had multiple amps sent to me with the 31n20s from ebay and the only problem was those transistors. They simply won't work. They run hot and fail prematurely.