HU cutting out...so is my brain!

[Onebeachbum05]

I have some serious noise w/ the car stereo. I will be home tonight doing some more night audio trying to isolate it after work. The ground loop part seems easy compared to the harmonic wherr...wherr.. wherr that starts of soft and picks up to a loud noise.
The ground loop isolator killed the ground loop so this other issue is separate for certain.

2005 4runner formerly w/ JBL indash cd changer
I checked wiring for the following and things seem to check out per the diagrams.
W200 alpine HU
PAC brake bi pass for video
PAC steering adaptor
Blackbird Navigation base

Genisis 4ch amp (40amp fuse)
1f cap


I can play the HU at low volume and it is fine. When I turn up the volume past low to normal listening level then the screen starts to flicker and then the unit starts to cut out.
I unplugged the Ipod and went to the Ipod source on the HU and it disappeared for a moment and then returned. No signal...no change.
Ran power direct 10g wire from the battery, 12g wire grounded at the batt, and then grounded from the HU to a heavy duty metal support 8" away. Tried using my jumper cables for ground from the batt to the HU...no change.
Removed the sub amp from the equation and changed the 4ch amp ground to bigger/shorter 8G and runs 24" to the CAP and from there a 4G wire 20" to the wire-brushed spot on the chaise.

Still a loud wherr wherr wherr with the volume at 0. It seems like something is grounding through the RCA's but what about the cut out at higher volume past 15.

I have done a series of checks like removing the antenna lead, signal leads, and tonight I will use the motorcycle battery pos and neg to the HU to see if that changes things.

Running out of ideas.
I don't think this is Alternator related as the sound does not change when I start the car or bring up the RPM's. The dome lights in the car don't dim either.

Any suggestions? I am hoping to acomplish something in the 2hrs I have to work on this tonight.

 

[tarheeltp17]

If you have a multimeter, put one side to ground and the other the the 12v constant going into your radio. Turn the volume up and if the voltage drops, there is your problem. You will also want to do this on the 12V switched wire (red wire). If you are running multiple sources off the switched source then that could be causing a voltage drop at the radio which could turn it off. You need atleast 11.5 volts to keep the radio on. It will probably drop off a little bit regardless, but as long as it stays at a respective 12v then you are fine.

If all of the above checks out fine, start eliminating problems by unplugging them. Unhook your RCAs to eliminate your external amps and so on... that's the best way to troubleshoot in my book.

 

[Onebeachbum05]

I did check the voltage but NOT the drop, and only at the HU constant and Acc wire. I will definatly check and am very greatful for the help.

At one point I did remove the RCA's completly but could only watch to see if there was flickering on the screen and none was noticable at high volume.

Is the very small grey 12v switched wire just a signal like the remote turn on wire or does it provide power?
There are 4 larger wires that should go to the one small Acc wire (brake over-ride, blackbird base, steering adaptor, HU.).

If the voltage drops at HU power increase is that an issue with the HU if the power is a 10G wire off the battery? I can't think that the battery does not have the balls to carry the load for a stereo

Thanks again.

 

[Onebeachbum05]

Isolated it to the back amp...glad that's over and thanks for the help.