I'm not experienced with high-power amplifier circuits and need some help. This Alpine MRP-M500 had a blown fuse when I got it. With a new fuse still nothing. The blue light does not come on. It looks like the 12v stops at the first transformer T9001. And the second transformer appears to be open. Is it worthwhile to try to find this transformer? Or is there likely to be other blown parts too? I couldn't find any shorted power transistors or regulators.
Since this is a car audio sub woofer amp I will move it to the car audio forum. There are some very knowledgeable people there who should be able to help you get this sorted.Edit: Moved
Good luck!
One 'transformer' is likely an inductor. The other is the power transformer.
Did you check to see if the transformer was open on the pins for the transformer or on the pads for the FETs?
Did you check to see if the transformer was open on the pins for the transformer or on the pads for the FETs?
Actually they are probably both inductors. It's 12v DC input, and power goes first through an inductor (says 4:4 on the label) and immediately into a second inductor. This second inductor appears to be open.
T9001 is an inductor. T9901 is a transformer. On the primary the outer terminals should read 0 ohms to the center taps that go to the inductor.
No pins on the input side show zero ohms to any pins on output side so the transformer must be burnt out. Is this likely the only thing burnt? Or could something else cause it to burn out? Is it easy to find a replacement transformer?
On the side with 8 pins, they are all shorted together. It is still soldered onto the board. On the other side, 12-15 are all shorted.
What resistance should I read on D9901?
What resistance should I read on D9901?
As I said, I'm not experienced with high power audio amp circuits, so maybe I'm making a mistake. I only have 12v power hooked up to it while I'm testing. No speakers, no input signal. I'm thinking that because the blue light doesn't turn on, there is a fundamental power issue. When putting my digital ohm-meter across the output transistors, FETs and diodes, I can detect no shorts.
With power on, Q9902 Q9903 Q9904 Q9905 all have 12v on the center pin. While Q4001,2,3,4 all pins are near zero v.
The 9000 series parts are power supply. They produce power for the rest of the amp. If the 494 doesn't have 12v, it's not driving the power supply to produce voltage so the rest of the amp won't have voltage.
More often than not with these amps, the output transistors fail and force the amp to shutdown (so the control IC won't drive voltage to 494-12).
More often than not with these amps, the output transistors fail and force the amp to shutdown (so the control IC won't drive voltage to 494-12).
Okay, thanks for your help Perry. I'm going to shelve this project for now. I just don't have enough experience to know what's going on here.
Just to confirm... did you have remote voltage applied?
This is a complex amp, especially if you don't have a lot of experience repairing amps. For general repair information, read through the basic repair page (link in sig line below).
This is a complex amp, especially if you don't have a lot of experience repairing amps. For general repair information, read through the basic repair page (link in sig line below).
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