Question about Pioneer GM-X372 Car Audio Amplifier

2 Answers

No audio to speakers from deck, just to amp

Hi i have a Pioneer DEH-4600MP which seems to work fine; however none of the car speakers make any sound regardless of the volume. What does apparently recieve a weak signal is my amp which powers a subwoofer. If I put the volume fairly high (like 35/62, while normal listening volume was maybe 10) I can hear the output from the subwoofer. The amp has a seperate input from regular audio cables (red and black out of deck). This setup worked fine when I purchased the car used, then came and went, and now just works as described above. All connections look fine (main cable bundle, antenna, and RCA cable). Could the deck have a bad internal amp or something? Let me know if any more information would help...thanks!

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  • TCab Apr 23, 2008

    Great troubleshooting steps; there was no voltage going to the speaker wires while the yellow seemed correct at a bit over 12 volts.

  • TCab Apr 23, 2008

    Actually; I realized I'm an idiot and when I first tested the unit wasn't ON so nothing would've been outputted anyway. When operating, 6 wires had the about 1/2 voltage deal (all about 5.4 out of 12.2), while one pair remained at zero. I did not test the external amp signal yet as I'm not sure of the steps on the BCAE page (although that site is awesome).

  • Anonymous Nov 18, 2008

    Hmm I have a similar problem. I have a VM9512 that powers up but no sound. I checked the voltages across each wire - 6 of them measured 4.5V. The other two are definitely messed up, one measured 11V and the other 0V. Would this mean the IC is bad or perhaps a user replaceable component instead??



2 Answers

For the pair that is at 0v, disconnect them from the wires that go to the speakers and re-test them. If they remain at 0v, they IC is defective. If they return to the voltage on the others, check the wiring between the speaker output wires and the speakers. Make sure they're not grounded anywhere.

Posted on Apr 25, 2008

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It's possible (probable) that the head unit has a blown internal amplifier IC. Measure the DC voltage on each of the 8 speaker wires on the head unit. Place the black lead on the chassis of the head unit. Probe each wire with the red lead. All should read approximately 1/2 of the voltage on the yellow wire. If you get some that are significantly higher or lower, disconnect all speaker wires from the harness and measure again. If the voltage is still not ~1/2 of the voltage on the yellow wire, the IC is almost certainly defective.

For the external amp, you need to check the shield ground for the head unit. The following page shows you how.

Test RCA shield ground

Posted on Apr 22, 2008

  • Perry Babin Apr 23, 2008

    If the head unit was on but the IC had no voltage on the speaker wires, the IC is most likely defective. There are a few (very few) head units that allow you to defeat the amplifier via menu control but I don't think you can do that on the 4600.

    Were the shields OK on the head unit? If they were and you have 12v on both the remote and B+ terminals for the amp (black meter lead on the ground terminal of the amp), the external amp may be defective also. The blown output IC shouldn't affect the RCA output signal.


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