greetings,

I have a stereo problem that I can't figure out. I'm a mechanic, but I'm electronically challenged!

I have a MY02 that I purchased from the original owner about 21 months ago. The original owner had Infinity 605cs reference series components speakers in the doors, powered by an Alpine MRV-T757 amp, and also an Alpine CD changer.

I don't think the tweeters ahve ever worked since I bought the car, and somehow I just kept putting off looking into the problem. Well, tonight I got out the amplifier manual and started trouble shooting. The first thing I notice is that the "protection" indicator is flashing red, which means it detects an "RCA groud floated" condition. What the heck does that mean? And where do I begin to look for the problem? I checked the ground and power wire connections where they connect to the amp, and to the car and they are clean and tight.

Any suggestions?

Thanks,
Markk

Edit to add: I'm using the stock head unit.

 

When the protection light on the amp comes on it means there is a fault with the amp or wiring side of things..
check:

Speaker wires are shorting out. (tweeters may be shorted out)
Amp is overheated..

Im almost certain its something to do with the tweeters.. if they arn't working then it may be shorted causing a closed circuit on the amps channels causing the protection mode...

 

yeah -- first thing to check is make sure that the tweeters aren't blown. if you're not hearing them, and the amp is giving you a protect mode issue -- they very well may be gone.


regarding what that actually means could depend a bit on what the manuf. means w/ their manual. my interpretation would be that the amp is getting a ground somewhere it isn't expecting it.

do you own a multi-meter?

if so, you'll need to get to the wiring in several locations. first start w/ the amp -- disconnect the speaker wires (be sure to label where they go if you might be unsure when going back together).

find a nice solid ground point, and check DC resistance from each speaker wire to ground. they should all be infinite.
also, check resistance across each set of speaker leads (check + to - for each speaker). they should be about 3.2-3.5 ohms.

next, get to the crossovers... that will depend on where he put them. they could be by the amp, could be under the dash, could be in the doors... hopefully, they aren't too hard to reach. again, label the wires so you can go back together as it comes apart. and again -- resistance for each individual lead to ground (not needed if they were all infinite above), and resistance across each speaker + to - (again, likely to be 3.2-3.5 ohms).

finally -- disconnect each of the RCA's from the amp. individually measure the resistance from center pin and outer sheath to ground. iirc, outers should read 0 resistance, centers should read infinite.

report back what you find, and we can go from there.

 

oh --- should have thought of this first....



before you start gutting everything (as i outlined above)

disconnect the RCA's from the amp. power the system up. is the little red light flashing still??

if so, then proceed w/ everything i listed above. if no, then just do the last step (measuring RCA's to ground).

 

Thanks PJK3!

Very helpful information. I do own a multi-meter and will check per your instructions when I get home tonight.

Thanks again!
Markk

 

np.

let me know, and if i don't respond, bump this in case i miss it.

 

PJK3,

I tore into it last night. I first checked to make sure the tweeters were actually there. They were, but the crossover was incorrectly wired. I straightened out the wiring and they work great, but I still had a ground problem. So I traced down the wiring from the H/U and found a "Audiolink - Powerlink II" convertor attached to the H/U output, converting it to RCA. This unit has a ground lug for amps that require it but it wasn't grounded. I'm going to fix that this weekend.

So it looks like I'm in good shape.
Thanks again!
Markk

PS.. Don't take your car to Pasadena Auto Sound in California.

 

cool.

interesting -- i like the, " first checked to make sure the tweeters were actually there" --

so -- crossover issue fixed.

and it sounds like they have a line level converter in there... http://www.linkmeup.com/prod03.htm

[QUOTE]Key Benefits
-Fully shielded aluminum enclosure for ultimate noise rejection

 

One more thing....make sure you tape up the tweeter wires. A lot of times people forget to, and end up touching when you put the door back on.