Audiopipe AP1800D

[rhempz01]

Repairing a power supply and output section of this amplifier. I just finished one that is of similar make. So following the same steps. I worked on this one. So the power supply went fine. Up and running had a shorted rectifier. (Should I replace them all?) Ok so output section the I did not replace the driver chips . Just the outputs with a test set of tested irf640. The amp powered up and all looked fine. When I attempted to add input, a 50hrtz 3v signal it blew two outputs in half. The same two that were shorted? Voltage regulator all have 5v. Would a bad op amp cause this?

 

[Perry Babin]

Gate resistors?

 

[rhempz01]

I'll recheck them.

 

[rhempz01]

With min input the amplifier has audio, it imeadatly is clipping badly as if the gain is all the way up?

 

[Perry Babin]

The gain setting doesn't alone determine whether the amp clips or not. The input level, the crossover setting, the bass boost are all part of the equation.

Is the rail voltage remaining constant?

What is the voltage swing on the output of the amp when it clips?

 

[rhempz01]

i cant leave it on long or it will blow an ouotput transistor. im going to remove all of them anf figure out what is going on in the output stage.

 

[Tom7227]

What the inductor look like?

 

[rhempz01]

Good, no darkened or melted spots, no evidence of heat anywhere. I have it working now.

 

[rhempz01]

Anyone know a part number for the 10k pets found on the Chinese style amplifiers?

 

[Perry Babin]

Mouser has some but you'll have to find something with the same pin layout and shaft that will work in your amp.

 

[ultra]

Have you noticed the one output fet on the lower side of the picture is brake open ? (Its the fourth from the left).