Nonfunctional car audio amp - can I fix it?

[jlee]

Latest pic:
solderedamp.jpg
Maybe I'll get lucky...we'll see when I try it out.

amp6.jpg
amp7.jpg


Update:
Well, someone fried something. Is this something I can fix? I'm thinking I'll need a fine point for my soldering iron..

Somewhat visible damage
Now you can see it <-- does all that brown melty stuff mean something is fried on the other end, or is it normal on circuit boards? This is my first time messing with one..

amp5.jpg <-- trying to get a better pic now.



Pic
Pic2

A friend of mine gave me a two channel Alpine amp (2x90w) that apparently doesn't work - I thought I'd try it again before I throw it away, since I really could use it now. I plugged it in and wired it to my subwoofer -- the amp gets power, but I get nothing from the speaker. I tried again on one channel (rather than bridged)..still nothing. It's getting ~14+v on power, and it's showing 5.xx volts on the + and - speaker terminals. If I set + to positive and ground on the -, my multimeter shows 0.

Is the amp shot, or is there something I could check/maybe fix? The fuse is good and my wiring is good (connected my other amp, and the speaker worked fine). The only iffy bit is the ground..I just rested the ground cable on the terminal, rather than screwing it in (large cable..tiny space for it), but the amp is getting/showing power.

Any ideas, or should I throw it away?

 

[Drakkon]

toss it...unless you feel like opening it up and finding the capacitor/resistor that has fried...

 

[BrokenVisage]

Another one bites the dust.. (Alpine product)

 

[godmare]

Originally posted by: Drakkon
toss it...unless you feel like opening it up and finding the capacitor/resistor that has fried...

what's so hard about that?

 

[jlee]

Heh, ok. No loss, fortunately, as long as I remember to pull my perfectly good fuse back out of it.

Any recommendations for a 4ch (or 4.1) amp for my MR2, along with a small sub to go with it? Needless to say, space is an issue.

 

[jlee]

Originally posted by: godmare

Originally posted by: Drakkon
toss it...unless you feel like opening it up and finding the capacitor/resistor that has fried...

what's so hard about that?

If anyone can give me a brief outline on how to test it, I'll give it a shot..I'm not really good with a soldering iron, but I can try.

 

[jlee]

Anyone?

 

[godmare]

I've never pulled apart a car amp, but have replaced caps before. Most of the time they were either physically evident to be nonworking (bulged or corroded, etc.), or replacement was compulsory based on behavior of the electronics, like in a cap kit for a monitor.

 

[jlee]

I took it apart..can't see anything obvious..pic in OP.

 

[Rubycon]

That appears quite toroidally limited for 90wpc product.

 

[Cattlegod]

check the internal fuse

 

[jlee]

Originally posted by: Cattlegod
check the internal fuse

Where might it be? I only know of the one accessible without taking anything apart.

Pic of outside

 

[jlee]

Up for the night crowd, then I'll let it die..

 

[Cattlegod]

it would be on the inside. the symbol on it should be ~

 

[jlee]

Originally posted by: Cattlegod
it would be on the inside. the symbol on it should be ~

I can't find anything resembling one..is there anywhere in particular I should look? I didn't see anything near the power terminal..should I remove the circuit board from the heatsink/case?

 

[jlee]

Aha..melty-ness! Think I can fix it?

 

[Cattlegod]

need some better pics of the back. the brown stuff doesn't matter. it bleads from the solder at high temperatures, don't worry about that. to me it looks like 2 of the traces have curled up, but i need some other pics.

 

[jlee]

Originally posted by: Cattlegod
need some better pics of the back. the brown stuff doesn't matter. it bleads from the solder at high temperatures, don't worry about that. to me it looks like 2 of the traces have curled up, but i need some other pics.

I'll take more - up in a minute.

The traces are curled back - they were broken, but I pulled them back so they would show in the picture.

 

[jlee]

I'm having a hard time getting my camera (Canon A40) to take a clear closeup..

amp5.jpg

I'm wondering if I can fix it just with solder. I bent the traces back down, and they almost touch.

 

[BUTCH1]

Try soldering some wire to "bridge" the bad part's of the
PCB.

 

[Mark R]

You might be in luck.

The bad traces are both supply ground potential to the speaker outputs. I'm not quite sure what could have caused them to blow like that other than connecting the amp wrong (connecting 12V to the a the speaker output ground).

If that is the case, the chances are that it hasn't done terribly much damage apart from burning out the traces. If you can put a nice solder bridge across the gaps, you never know, it might work.

 

[Eli]

Looks fixable to me..

Just bridge the traces any way you can, and see if it works...

 

[jlee]

solderedamp.jpg

I have to wait for my car to get back, then I can try it out.