Sound fades from 3 channels and the 4th channel gets real staticy and LOUD

[Reboot]

Hi all,

I am having a wierd issue with my truck system and cannot replicate the issue, it is very random yet common. I have an alpine pdx 4.100 amp pushing 4 component speakers. It seems at random times the sound from 3 channels starts to fade getting more quiet and the remaining 4th channel gets louder and louder and static. I have to quickly turn the radio all the way down. I am currently sound dampening my truck so i have all my intererior pulled out and that allowed me to check all my wires and none of them are crushed by seats or anything. All the wiring seems fine. I contacted the alpine repair center and its going to start at 115$ and go up in price depending on repair. Yet i do not know if it is even the amplifier. Maybe it could be the headunit?

Have any of you experienced this before or know of a reason or cause for this to happen? Amp? HeadUnit? Grounds? Anything?

When it does happen it seems like it doesnt fix itself for sometimes over an hour so you cant listen to the radio. Turning off the truck, turning off the radio, turning off the amp does not seem to fix it. Yet it fixes itself, you will hear the 4th channel get quieter and the other channels gain volume.

So wierd!

Thanks guys!

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[Louisiana_CRX 5,000+ posts]

Hi all,
I am having a wierd issue with my truck system and cannot replicate the issue, it is very random yet common. I have an alpine pdx 4.100 amp pushing 4 component speakers. It seems at random times the sound from 3 channels starts to fade getting more quiet and the remaining 4th channel gets louder and louder and static. I have to quickly turn the radio all the way down. I am currently sound dampening my truck so i have all my intererior pulled out and that allowed me to check all my wires and none of them are crushed by seats or anything. All the wiring seems fine. I contacted the alpine repair center and its going to start at 115$ and go up in price depending on repair. Yet i do not know if it is even the amplifier. Maybe it could be the headunit?

Have any of you experienced this before or know of a reason or cause for this to happen? Amp? HeadUnit? Grounds? Anything?

When it does happen it seems like it doesnt fix itself for sometimes over an hour so you cant listen to the radio. Turning off the truck, turning off the radio, turning off the amp does not seem to fix it. Yet it fixes itself, you will hear the 4th channel get quieter and the other channels gain volume.

So wierd!

Thanks guys!

You can get a rca to headphone jack and use your phone to get signal to your amp ..that way you can test the amp ..just play some music from your phone to see if it fades out ..if it does you’ll know it’s your amp

 

[Reboot]

The thing is, it never does this until i am driving. I can sit in my truck all day and never move it and it never has this issue. Once i drive it, it may or may not do this. Which made me think it was wiring getting jar'd around by driving and causing a short in a ground but all my wires are good :/ It hasnt done this for 2 months, then 2 weeks ago i took a 20 hour round trip across 4 states and it did it 5 times on the road.

 

[Louisiana_CRX 5,000+ posts]

The thing is, it never does this until i am driving. I can sit in my truck all day and never move it and it never has this issue. Once i drive it, it may or may not do this. Which made me think it was wiring getting jar'd around by driving and causing a short in a ground but all my wires are good :/ It hasnt done this for 2 months, then 2 weeks ago i took a 20 hour round trip across 4 states and it did it 5 times on the road.

You didn’t happen to ground to a seat bolt ? Reason I’m asking I’ve seen similar problems where someone tried to ground with a ring terminal to a seat bolt ..well most seat bolts are coated with a sticky anti seize that doesn’t allow the system to get a proper ground ..in trucks I always ground to the frame ..the cab itself is isolated by bushings and doesn’t get that solid of a ground either

 

[Reboot]

You didn’t happen to ground to a seat bolt ? Reason I’m asking I’ve seen similar problems where someone tried to ground with a ring terminal to a seat bolt ..well most seat bolts are coated with a sticky anti seize that doesn’t allow the system to get a proper ground ..in trucks I always ground to the frame ..the cab itself is isolated by bushings and doesn’t get that solid of a ground either

No, the ground is a dedicated drilled hole into the cab with a bolt and nut. On the underside of the cab on the SAME bolt and nut another cable goes from there to the frame. So the amp grounded very well from the amp to cab bolt from cab bolt to the frame.

I have a headphone to rca cable i can use and test your elimination theory, but doesnt a heaphone jack put out too much volts for the preamp input?

 

[Louisiana_CRX 5,000+ posts]

No, the ground is a dedicated drilled hole into the cab with a bolt and nut. On the underside of the cab on the SAME bolt and nut another cable goes from there to the frame. So the amp grounded very well from the amp to cab bolt from cab bolt to the frame.
I have a headphone to rca cable i can use and test your elimination theory, but doesnt a heaphone jack put out too much volts for the preamp input?

I’ve never tried it ..I’ve just heard of people testing amps that way ....I have a tone generator with rca jack I use for testing input ..most people don’t have spare decks laying around to test with another deck and it does sound like you have your ground covered well