Amp troubles

[9-3turbo]

Hey everyone,

I have a 1/2 Farad cap, Crunch 175.4 AMP, 2 MTX 6x9s rated at 100W RMS each and a single 12" Sony 4 ohm sub that I'm having a problem with. When I turn on the head unit all the speakers hooked up to the amp make "noise" for 2-3 seconds. This noise is like pulsating static. Then although the amp is on and the protection light is off absolutely no sound comes from the speakers. This started recently after the amp would simply turn off once the sub started working. Even with the gains on fairly low, whenever I turned the music up, the amp would turn off after 10-20 seconds.

Tech support said it sounds like there is a bad ground and the amp might be trying to ground itself through the RCA cables. I checked and moved the grounds to a better position less then a foot from the amp/ cap. Also I checked the other speaker/ power cables. The positive cable to the cap did not have a good connection at all which I thought fixed the problem as at least the amp was always on now. However no sound from speakers.

I'm not really sure what's going on, I was thinking maybe I damaged the amp but lack of power should make it simply turn off?

Any help would be appreciated.

Click to read more...

 

[9-3turbo]

I changed out the speakers with no change in results, At power on I get a small blip in sound then nothing, just from the right rear speaker.

 

[SlipTap 10+ year member]

I guess i'll start:

check all of your fuses, check your grounds (again) . . . make sure that the chassis is sanded of paint/rust where the ground is, make sure all of the wires are tug proof.

After that, I'm not quite sure... your itself starts ok, windows work fine?

Send a pic of your setup/wiring . . . maybe we'll catch something.

edit: try removing the cap from the equation, and hook your cables directly to your amp. What kind of wire are you powering it with.

I'm assuming your other 2 channels of the amp are actually bridgeable at 4 ohms (i . e . try running 2 channels with your 6 x 9s, one channel for your sub, and leave one open).

 

[9-3turbo]

Removing the cap was a good idea, actually just tried that.

Without the cap it seems to barely be getting power... So I'm guessing it will work occasionally with a charged cap then the cap is emptied and it can't get power fast enough. The system is becoming extremely unpredictable though, sometimes the amp stays on and the speakers stay off, other times the entire thing shut down.

I'm going to try and get a hold of a multimeter tomorrow for a few hours and test at every point for a 12v line. When I'm testing wires not near the amp can I put one end on the positive wire and one end on the chassis? I've never used one of these outside of the classroom before.

Thanks for the responses

 

[SlipTap 10+ year member]

Removing the cap was a good idea, actually just tried that.
Without the cap it seems to barely be getting power... So I'm guessing it will work occasionally with a charged cap then the cap is emptied and it can't get power fast enough. The system is becoming extremely unpredictable though, sometimes the amp stays on and the speakers stay off, other times the entire thing shut down.

I'm going to try and get a hold of a multimeter tomorrow for a few hours and test at every point for a 12v line. When I'm testing wires not near the amp can I put one end on the positive wire and one end on the chassis? I've never used one of these outside of the classroom before.

Thanks for the responses

Yes, assuming the chassis point is a reasonable ground point (I. E. not rusty, no paint etc...) good luck finding one //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Also, check on both ends of your fuse block. I had one of those cheaper, circular fuse blocks, and got a loose connection of the amp side of the fuse block, which denied me power.

Are you positive that your battery is charged? Take your DMM and test the voltage at your AMP's + and - Terminals for power . . . the voltage should read around 12V (anything higher is perfect). If you're getting 12+ volts at the power terminals, then it isn't in your wiring, it's the amp. If you aren't getting 12+V, I would start going through your wiring.

Thats DC voltage, btw //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[9-3turbo]

The battery should be fine, just got a new one Sunday. I was hoping the old battery was part of the problem but no change. I'll check around at different points tomorrow and see what I can come up with.

Thanks Sliptap

 

[SlipTap 10+ year member]

no problem . . .

any news?