Working with an Alpine MRD-M501 with no sound. Doesn't give any error codes or outward signs of trouble, but shows no voltage at the drain of all four MOSFETs. Does that mean they are bad or do I need to check further upstream. Any insight would be greatly appreciated.
You need to compare all of the voltages on the microcontroller in your amp to those in the service manual. It's likely that some fault is causing the microcontroller to shut down the supply voltage to the PS driver IC. You can confirm that with the voltages in the manual for that IC as well.
You should be aware that these amps can be difficult to repair.
You should be aware that these amps can be difficult to repair.
Thank you once again for your time, Perry. I did a little checking on the controller, and found voltage absent on at least one terminal. Do you think the amp is worth the time/trouble to investigate further?
The decision as to whether it's worth the effort has to be made by you.
Which pin on the microcontroller had the wrong voltage?
Which pin on the microcontroller had the wrong voltage?
I was mistaken. It is in fact the source terminal on the FETs that has no voltage. There are actually several terminals on multiple ICs that are getting no voltage that should be, according to the manual.
The microcontroller IC is the one that's critical. The inputs and supply voltages to that IC determine whether it will tell other the rest of the amp to power up.
Have you checked all of the output transistors to see if any were shorted?
Have you checked all of the output transistors to see if any were shorted?
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