Audiopipe ap 1800.1 output drivers

[Shane73]

I have an Audiopipe ap 1800.1d. When I received it, someone had already attempted repairs to it. The power fets and gate resistors were bad so I replaced them. I pulled the outputs out and the amp powered on fine. Some of the outputs were missing when I got the amp, so I replaced all the outputs; however the amp goes in to protect when power is applied now. I beleive the output drivers are bad but can not find what part number I need to order. Thanks

 

[Perry Babin]

It's better to troubleshoot the circuit than to blindly replace parts.

Do you have a scope?

 

[Shane73]

Unfortunately, I don't have a scope.

 

[Perry Babin]

With no outputs in the circuit, measure the DC voltage across the gate and source (black probe) legs of the output transistors. Confirm that all on each side read the same and then post the voltage for the outputs on each side of the amp.

 

[Shane73]

I measured the voltage as requested. I get equal voltage across all transistors per bank; however, 1 bank reads 5.192 volts and the other bank reads 5.297.

 

[Hexhclass]

post a pic of the board and a close up one of the output section.

 

[Shane73]

Pic of board

 

[Shane73]

Close up of output

 

[Hexhclass]

Drivers:

2T MMBT4403

2X MMBT4401

 

[Perry Babin]

Various meters will give different reading on DC voltage with pulsed waveforms but the driver voltages would seem to be OK.

If you replace them, measure the same points to see if they have changed significantly.

 

[Shane73]

Thanks. I will give you an update.