Pioneer DEH-P860MP RCA grounding problem

[Jexx]

I recently purchased and installed a Pioneer DEH-P860MP and it was working great. I then shifted it around a bit, and now there is some major static coming through the RCA outputs, I hear this is common and is related to some type of grounding problem? What can be done to fix it? There is no noise from the head unit's internal amp...

[Perry Babin]

There is a bare power wire somewhere if the shield ground has burned. That needs to be repaired before you do anything else.

To check the shield ground, disconnect all RCAs from the head unit. Set you meter to ohms. Touch the black lead to the case of the head unit. Touch the red lead to the shield of the RCA output jacks on the head unit. You should get a reading near zero ohms.

If the shield ground is burned and the HU is under warranty, see if they'll repair it under warranty.

[Jexx]

Should the head unit be on or off when I'm testing it?

I'm pretty sure I did burn out the shield ground...exactly what is it? The head unit isn't under warranty...

[Jexx]

By the way, how did I fry the shield ground? There actually was a bare power wire!

[Perry Babin]

It doesn't matter whether the head unit is on or off so you should do it when it's off.

You burned the ground by allowing a 12 volt power source to contact a ground circuit that was not capable of handling as much current as the fuse in the 12 volt power line.

The least invasive repair is to use external jumpers. Since the internal fusing (either a trace or a surface mount fuse) is no longer available to limit current if this should happen again, I suggest you fuse the jumper wires. The small 5mmx20mm fuses and holders available from radio shack will suffice. A 1 amp fuse in each will offer good protection and will not blow under normal operating conditions.

The attached photo and the one in the next post show the connections. You solder one end of the fuse holder to the RCA cable shield ground. The other end of the fuse gets connected to the head unit chassis.

[Perry Babin]

Close-up of shield.

[Jexx]

Thanks so much, Perry! No more noise and the bare wire has been fixed!

[Vanquish]

Dear Perry,

I have the same problem with a P88RS. I disassembled it and I can see an SMD fuse next to the RCA Ground. Do you think this FUSE can be the source of the problem? What is the type of this fuse ususally? 1 OHM can be enough?

Thanks in advance,

Vanquish

[Perry Babin]

Does it have a number or letter on it?

Have you measured the resistance across it (with the head unit completely disconnected from power source and amplifiers)?

[Vanquish]

Originally posted by Perry Babin
Does it have a number or letter on it?

Have you measured the resistance across it (with the head unit completely disconnected from power source and amplifiers)?

Dear Perry,

I can read the follows above the fuse: FU351, and there is a "P" letter on the fuse itself. I'm almost sure that this fuse can be the problem, this is the only connection between the house ground and the RCA ground, if I measure it shows unlimited resistance. I will try to replace it, the only question is the type of the fuse, what do you think? 1 Amp is ok?