Help! My amp isn't working!

[Timi]

So I'm not talking about my guitar or bass amps, the amp in my car stereo setup decided to stop working yesterday. As luck would have it, the very same day I spent a lot of money on new speakers for home....

I thought I would try here before going a car audio forum and getting a stupid answer from some 16 year old boy racer. For the record, I sometimes listen to music loud but I don't put the system past its limits. I have a decent stereo in my car because I enjoy music, not because I have a small penis.

Basically the amp is powering on for 5 seconds or so before the LED slowly starts dimming until it is off. After a few seconds it comes back on and repeats this process. For the brief time it is on no audio can be heard.

There is no problem with power getting to the amp. I am getting around 12v (when the engine is off) from the remote switch wire from the head unit and the power wire connecting direct to the battery (via a fuse of course). I have also disconnected all the speakers just in case a short in a speaker wire was causing the amp to freak out. I am fairly confident the actual amp is at fault.

I was thinking perhaps something to do with capacitors in the power supply section of the amp but I could be way out. Anyone got any ideas?

[head_strong]

have you checked the earth and the 12v supply to the amp (from the battery, not the remote wire)? could be lose/not good earth. (make sure there is bare metal where its connected to the car body). also check fuse is in properly, just basic things. if none of this works it might be more serious.....

edit- since its doing the same thing over and over again, try checking the power into the amp (12v from battery, and earth) and if it remains constant while the amp is turning itself on and off then it is most likly the amp.

[Timi]

I am getting around 12v (when the engine is off) from the remote switch wire from the head unit and the power wire connecting direct to the battery

I have tested everything except the amp properly and it all works, as it has done for seven years. I'm more looking for advice of amp electronics as that is where the problem is.

[the_haunted]

It's Usually a short output transistor in car amps (there's not much to them).
Do you have a multi-meter? if not take the cover off and see if you can see anything toasted.
what's the make/model also?

[rocklander]

I thought I would try here before going a car audio forum and getting a stupid answer from some 16 year old boy racer. For the record, I sometimes listen to music loud but I don't put the system past its limits. I have a decent stereo in my car because I enjoy music, not because I have a small penis.

Basically the amp is powering on for 5 seconds or so before the LED slowly starts dimming until it is off. After a few seconds it comes back on and repeats this process. For the brief time it is on no audio can be heard.

There is no problem with power getting to the amp. I am getting around 12v (when the engine is off) from the remote switch wire from the head unit and the power wire connecting direct to the battery (via a fuse of course). I have also disconnected all the speakers just in case a short in a speaker wire was causing the amp to freak out. I am fairly confident the actual amp is at fault.

I was thinking perhaps something to do with capacitors in the power supply section of the amp but I could be way out. Anyone got any ideas?

it takes a big man to admit that.. no wait.. it takes a small. oh.. um.. never mind.


workmate installed a new stereo from supercheap in his car late last year. went fine for a while then similar stuff started happening. turned out to be a lead had come loose from the speaker and was shorting out against the inside of the door. that dragged the output down to earth.. could be worth a check.

[angry_young_poet]

so you like the doof doof?

[Krucifier]

I reckon the_haunted is right, output FET has died. Probably not worth repairing unless you're able to do it yourself or it's an especially good amp.

[Timi]

Yep I've checked some of the transistors and I'm pretty sure some of them are bung. I was reading a thing about how to test them last night and some seemed to show what the website said would be a bung transistor.

Its a seven year old fusion amp, I'm just gonna replace it, with something a bit better too.

Also, I appreciate any advice but if you are going to offer advice please read my original post.....

[thehenderson]

Which band were you playing when it broke? This is vital

[slash-ed]

Avril

[thehenderson]

Too much Fu Manchu for one stereo is bad for it's midrange response

[Timi]

I think it was actually Fu Manchu.....
Wasn't running it very loud either.

[rocklander]

Also, I appreciate any advice but if you are going to offer advice please read my original post.....

fair call, guess I didn't clarify. he disconnected the speakers too.. at the amp end. not sure from your text if you disconnected from both ends, or disconnected them (at stereo end) and things still failed etc.
and the loose wire earthing out (inside the door) could be putting enough short to dirt meaning no load on said xsistors to kill 'em.