p nut

EDIT: Edited the title. The problem is with my amp, not my HU.

I've got an older Alpine cda7845 and it's all of the sudden quit playing. It will intermittabtly come on for a few minutes and turn off again. The display is powered up still and shows the radio station or the cd min:sec display, but no sound. Is it done for? It was installed years ago, so no dice on warranty. Besides, it was Circuit City.

The connections in the back look good. Time for a new HU?

Second part of the question is, I have an Alpine CD changer, so in order to use that, do I need to go with an Alpine HU?

Thanks.

EDIT: Ok, I guess it might be the amp (MTX Blue Thunder Pro 504). No power going to it. Fuses are good. The blue wire seems to be connected ok. Maybe the amp's toast?

If it is, I'd rather not even mess with replacing it. Is rewiring to work without an amp going to be a headache?

fcm

There are two things I would check, if the fuse in the amps power cable is an AGU fuse, [large glass type] replace it even if it looks good, problems with AGU fuses are common.

I would check the speaker wiring and speakers from the amp, an amp that works intermittently may be going into protection mode because of a short.

Disconnect all speakes from the amp and reconnect them one at a time turning system on and trying it each time, if it is a short, [amp in protection mode] once the speaker/speaker lead that has the short is disconnected from the amp, the amp will start working again.

How much of a "headache" rewiring the system will be will depend on your skill level, the tools you have and how the system is wired now, speakers mainly. 94

pi Ka chuuu

bump

p nut

fcm - Thanks, man. You've always given great advice. I will change out that power cable fuse. Hopefully, that's all it is.

Also, the power LED light on the amp comes on when there is sound, but turns off when the sound stops (I know how obvious this sounds :D). My question is, when the amp goes into this protection mode, does the power LED light stay on? I guess it might depend on the make/model. Here is a pic for reference:



And the fuse:


And this is how clueless I am at ICE stuff---the speaker wires are the black wires, right? And they need to be all disconnected and connected back up again until a short is found? (I'll label them to where they go). Thanks for your patience with me.

Thanks again for the help. And thanks pi Ka chuuu for the bump.

EDIT: Changed out the fuse and still the same problem. Will work on the speaker wires tonight and if it's still giving me problems, the local shop says $10 for testing the amp.

fcm

Do you have a multimeter or 12V test light, if so test for power on the amps power lead at the amp, also test for power on the control lead at the amp when system is on and not working.

Also, I can find no info on your amp, not even at MTX support, [archive... http://www.mtx.com/caraudio/archive/...lueThunder.cfm ] where did you get the amp? 94

p nut

fcm - Any idea what the readings should be at either terminal? I'll test them tonight.

A suggestion was also thrown out to take the amp and hook it up to the battery with some speaker wire to test it. Seems simple enough.

The amp was purchased at Circuit City back in 01.

p nut

Ok, figured it out!!! Before I unhooked the speaker cables and started testing voltage, I wanted to test out the remote wire. So I took a piece of wire from the remote terminal and hooked it up to the battery. And voila, it works. So there must be some sort of a short somewhere, and I'm guessing it's right behind the HU. I'll have to tear into it this weekend. Thanks, everyone.

fcm

Strange I can not find it at MTX, maybe so old it's deleted.

The amps power lead, [red with red insulator] should read at least 12V with system on.
The amps ground, [red lead with black insulator] should read full continuity to ground, with system on.
The amps control lead, [blue] should read at least 12V with system on.

Voltage can be as high as 13.5V -14.5V with engine running and RPM up, any higher and you have a problem with the alt., some amps will turn off if there is too much voltage, over-voltage is not your problem if amp does not work when engine is not running, [alt. not supplying power].

If you have power and ground at the amp, connecting the amp to batt. with speaker wire is not going to help, if you do not have "good" power and ground at the amp then you have found your problem, either way the best way to troubleshoot the problem is with the amp mounted and wired with it's power and ground leads, [and control lead].

Are you using a multimeter or 12V test light to test for power and ground?

Sorry, yes, the speaker wires are the black ones, and don't worry about tagging them, it's not hard to figure out where they go, disconnect them one at a time, when you disconnect the short, the amp will stay on, because indicator light goes out, check for good power and ground at the amp first.
One more thing, the amps power lead fuse holder is connected using two 8a butt, [crimp] connectors, one of them under what looks like shrink tube and electric tape, remove the tape and check those connections, ["tug" on the cable at each end of the connectors] they should have been soldered and covered with shrink tubing, same goes for the ring terminal at the batt., [soldered to cable]. 94

p nut

fcm - Thanks for the info. Very detailed and insightful. I do have a multimeter, but I have narrowed it down already to the remote wire. What I'll probably end up doing is replacing the whole wire and hope that that will do it. I have ghetto rigged it currently and just hooked up a small wire from the remote terminal to the power lead terminal (will unhook it when not in use).

However, if replacing the wire doesn't do the trick, can the actual harness be bad on the HU? That's going to be a headache.....