Bad/Open RCA Shield on Pioneer DEH-P7100BT Head Unit

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paulieb81

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Joined 2009
#1
I have been chasing a nasty engine whine in my system all day, checking every wire and ground there is. Finally after an entire day from noon to almost midnight, I have found my answer through searching on here and testing.

It is an open RCA Shield on my head unit as directed here:
RCA Shield Repair

I did this simple test, and all noise went away.

Now previously two weeks ago, I blew an Alpine MRD-M605 amp here:
blown alpine mrd m605 amp

I am not sure if these two are related, or if the blown amp caused the ground in my new head unit to blow. If anyone could shed any light on this please let me know.

My Pioneer DEH-P7100BT head unit is brand new, only two weeks old, I could exchange it or repair it, please advise what would be the best course of action.
 
#5
I understand that, but whatever installation mishap I may have done that caused the open shield, could that have also blown the amp?

The weird thing about the amp being blown, is that it worked just fine for two days, then the 3rd day, I turned my truck off to go eat lunch, when I came back out, it was not working.
 
#9
not sure if this also goes along with this problem, but I noticed that when I had it hooked up the other day, my gain on my amp was all the way down to the minimum. The head unit is supposed to put out a 4v signal therefor should the amp not also be set for 4v, rather than 100mv? As I turned the gain up, the sound went down, therefore lowering the amp output.
 
#10
The reason the fuse blew most likely is you disconnected the amp ground before you pulled the rca's causing the radio to act as a ground for the amp and popping the fuse. With a pioneer deck all equipment including the deck should be properly grounded before connecting the rca's or you blow the picofuse. I also found out the hard way, and used a single strand of 32+ awg wire to bridge the fuse. Perry is right that sucker is tiny. I have a mainboard for a deh-p780mp here I will try to take a pic of it later tonight to show you.

Zippy

Also it had nothing to do with the gain
 
#12
Only a few amps (some MTX and some 'defective' Rockford amps) will try to ground through the RCAs if the amp loses the chassis ground. Removing the fuse feeding the amp prevents a lot of potential problems (although, most people seem to be too lazy to do it).

The problem (shield grounds opening) is generally caused by having an uninsulated power wire and a set of RCA cables sliding around in the vehicle after the amp is removed. If the power wire touches the shields of the RCAs for even a tiny fraction of a second, the shield fuse blows.
 
#13
Based on the link I posted about the temp fix for the open ground. The article said to use a 1 ohm 1/4 watt resistor. My local radio shack stocks a 10 ohm 1/4 watt resistor. That's the closest they get. Will that work? If not what would be your recomendation?
 
#16
hmmm... well not simple enough of course. While taking this example:
RCA Shield Repair

Instead of soldering the ground onto the rca cable, I was thinking it would be a better long term option to solder it to the RCA jack, but its such a tight squeeze without touching the outside of the radio, therefore negating the fuse.

Any suggestions? Or just suck it up and solder the damn thing onto the RCA cable and call it a day?
 
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