# Audiobahn amp turns on briefly



## BassinBurt (Mar 20, 2014)

I have an old Audiobahn A8000T amp that I am trying to repair. When I bench tested it some of the FET's would catch fire. I replaced the FETs and tested again. They no longer catch fire, but the the amp will turn on for a second then turn off. When I remove power from the amp it will turn on for a second and turn off again. I'm new to this stuff, and am doing this for learning purposes. Any suggestions?


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## BassinBurt (Mar 20, 2014)

There isn't any other visible damage, and nothing seems loose. Kind of stumped.


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## BassinBurt (Mar 20, 2014)

Exactly what I figured. No one actually knows what they are talking about on here.


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## TallTexan (Dec 14, 2007)

Dude: Check out the car audio section on DIY Audio (Car Audio - diyAudio. Perry Babin is very knowledgeable over there and will most likely answer your post (but doesn't accept forum private messages). Good luck.


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## soccerguru607 (Nov 4, 2009)

We have guys repair amps on this forum but you should add pictures and explain what you have replaced and done to the amp.


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## ATOMICTECH62 (Jan 24, 2009)

I was about to help him until I saw his last post.


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## soccerguru607 (Nov 4, 2009)

Should be respectful when asking for help
Actually should always be respectful and nice no matter the situation will get more things done


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## ATOMICTECH62 (Jan 24, 2009)

I dont mind helping people but it can take time with research and digging through piles of amp's to look at a resistor or something.
So when they get an attitude I run out of time real fast.


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## TallTexan (Dec 14, 2007)

Also, this part of the forum doesn't get the large number of eyeballs on it as others here.

Off topic side note (system envy):

Atomic: I like your setup in your sig line. I've had a pair of the GTI608 and they are some nice hefty, well built speakers. The Kilppel test on the newer version 660GTi as very impressive. I'm also a Mac guy. Been thinking about 3 way up fronts with Faitalpro-3fe22 3" mids with their high 91db sensitivity and reasonable price (sub $75 for a pair).


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## vwdave (Jun 12, 2013)

Honestly, I never like audiobahn stuff so I'm not likely to come in here.

Even though you seem like a prick, I'll try to row a few pieces of info your way...

Try replacing the PWM chip(s). I had a similar problem and it was my PWMs. It could also be the input diode.


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## ATOMICTECH62 (Jan 24, 2009)

I think he bailed.


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## BassinBurt (Mar 20, 2014)

I apologize for my frustration, guys. I'm just trying to understand circuit boards. I'll post some pictures later today, and also explain what I have replaced.


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## BassinBurt (Mar 20, 2014)

And thanks Texan. I will see if I can find anything in that section, too.


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## soccerguru607 (Nov 4, 2009)

I don't know how skilled you are in car amp repair but google Perry Babin, he sells dvd tutorial for repair car amps. You should buy that dvd to learn how to repair the right way if you are not a pro tech. like Atomictech62 or Trickyricky or Shawnk?. So when you ask question techs. will understand you better. I have like 5 or 6 copies here through a dozen year+ with updates. I can not give my old copies away or sell them because most are gift from Mr. Babin.

edit: You will also learn most guys are nice and forgiving here. They will help you to their capability and there are never any jealousy involved.


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## BassinBurt (Mar 20, 2014)

I replaced these MOSFETS on both side of the board, except the all black one. As well as the diode.


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## BassinBurt (Mar 20, 2014)

When I tapped the left, and middle cap they had a little rattle to them. Good sign of them being bad?

I appreciate the help guys. Is there anything else I can test?


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## diatribe (Aug 11, 2008)

Did you see this repair done by dbr?

http://www.db-r.com/Extras/index4.html

Swinging away with Tapatalk


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## BassinBurt (Mar 20, 2014)

This was my first time soldering on a circuit board, clearly I had some trouble lol. Could there be an issue with that?


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## ATOMICTECH62 (Jan 24, 2009)

Absolutely.
There is a lot of current that passes through those solder connects and the load is shared by the mosfets since they are in parallel.The solder should flow over the lead and trace on the board so looks like every other connection on the board.
Heat the lead and trace then apply the solder.
Have you checked the output mosfets for shorts?
If not,the new mosfets will explode again if even one output is bad.


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## BassinBurt (Mar 20, 2014)

Resoldered the connections and the amp is still turning on for a few seconds then turning off. However, this time I hooked it up, it turned on for a few seconds, then turned off. But when I took power away and hooked it back up, it wouldn't do anything. Still, nothing appears burned or bad on the board. I just ordered some capacitors, so I'm gonna give that a try now.


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## vwdave (Jun 12, 2013)

Did you use a multimeter to verify continuity where it's needed? The FETs have one power leg, one ground leg, and one gate leg that connects to the gate resistor. I'd make sure that those are making contact where they need to. The power legs should all connect up to the power wire terminal, same for the ground leg. Gate leg should lead to a resistor then back to your PWM. That PWM could also be dead.

Also you have lots of resistors, I'd go through and test each of them to make sure that a fusible resistor didn't blow.

I don't think it's caps.


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