# Amp keeps blowing fuses



## Steve1828 (Sep 6, 2011)

Well first off. I am a noob here and hello everyone. So I have a Punch 900 amp with a 12" sub in my truck. Last week I disconnected the box to make more room in my truck when we went out of town. The other day I put the box back in. I noticed it wasnt working. So I checked the fuse up at the battery and it was blown. I replaced it and as soon as I turn the key you can hear the amp kick on or a pop through the sub and then nothing. The fuse blows instantly. So I checked all the wiring and tried again. It did the same thing. So I pulled the amp and stuck it under the hood and used the same wiring and remote wire and went straight off the battery and the amp powered up. I did not have the sub hooked up to it though. I didn't have enough wire to do that. Any ideas as to what is causing this? The amp will power up just fine without the sub hooked up to it. The minute you hook the sub up the fuse on the power cable for the amp blows. I have tried another sub, RCA's and the adapter I am using for the rca's and it still blows. I have it set up bridged. I am lost now other than to replace the amp. Just makes no sence to me why the amp powers up and doesn't blow the fuse until the sub it hooked up.


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## spl152db (Dec 20, 2007)

few things. what size fuse are you using? 
did you try leaving it in the rear without the sub hooked up to it? 
btw don't hook up amps without fuses. the wire can handle a lot of power but you're basically using the wire as the fuse when you do that. it will heat up and likely catch fire doing that.


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## dragonrage (Feb 14, 2007)

Don't just replace fuses. Fuses blow for a reason. Either your load is too much (too low an impedance for the amp or there's a short in the wiring or the voice coil of the sub) or the amp is in need of repair. If the amp is not in need of repair, then you could end up putting it in need of repair if you just replace fuses and try again.


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## Steve1828 (Sep 6, 2011)

I have put the amp back in the location where it has been for 6 years. The amp powers up by itself without the sub hooked up. Hook up the sub and the fuse blows. The fuse thats in there is a 40 amp. Its the size fuse that came with the amp install kit. It's worked fine for 6 years now.
*I will explain detail how this all came about: *A couple weeks ago I disconnected the speaker wires out of the back of the box that the sub is in. I left them hooked up to the amp. I removed the sub box to make more room for people as we were going on vacation. We came back and I put the box back in the truck and hooked the speaker wires back up and when I started my truck I realized it wasn't working. So I looked under the seat at the amp and seen it wasn't on. So I checked my fuse where my remote wire is going to and it was fine. So I popped the hood and checked the fuse on the power wire up at the battery and it was blown.


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## sqshoestring (Jun 19, 2007)

Put a meter on the speaker leads and power it up with no RCA. If you see voltage there more than 1v DC at the most the amp is toast. If the outputs are shorted an amp will do this and have power on the speaker outs with no input. Usually not that hard to repair though some RF have soldered transistors that are a pain.

If you let the speaker wires touch with the amp on and connected, it would blow the amp or put it in protect.


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## Steve1828 (Sep 6, 2011)

sqshoestring said:


> Put a meter on the speaker leads and power it up with no RCA. If you see voltage there more than 1v DC at the most the amp is toast. If the outputs are shorted an amp will do this and have power on the speaker outs with no input. Usually not that hard to repair though some RF have soldered transistors that are a pain.
> 
> If you let the speaker wires touch with the amp on and connected, it would blow the amp or put it in protect.


So are you saying to disconnect the rca's at the amp and disconnect the speaker leads at the box and then put a meter on the bare leads of the speaker wires there?


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## spl152db (Dec 20, 2007)

yes thats what he's saying. 

also did you protect the speaker wire when you removed the subs? your lead ends should not touch.


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## Steve1828 (Sep 6, 2011)

spl152db said:


> yes thats what he's saying.
> 
> also did you protect the speaker wire when you removed the subs? your lead ends should not touch.


No like an idiot I didnt. My wife shoved some stuff up under the seat where they were laying at. So i'm sure they touched one another.


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## spl152db (Dec 20, 2007)

oh man... sounds like you may have shorted the amp. but don't get discouraged yet! are there fuses on the amp? did you check them?


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## Steve1828 (Sep 6, 2011)

spl152db said:


> oh man... sounds like you may have shorted the amp. but don't get discouraged yet! are there fuses on the amp? did you check them?


If there is any on the amp. They are inside the amp. There's nothing on the outside of the amp. I haven't pulled the cover off yet to look at it.


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## Steve1828 (Sep 6, 2011)

The fact that it powers up with no sub hooked to it though would make me think that there are no fuses at the amp inside it.


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## sqshoestring (Jun 19, 2007)

If it powers up and you have something like 20-30v on the speaker leads, the outputs are toast. Not a bad repair because the power supply is still working at least, it can blow that too. Its better to take wires off the amp then nothing can touch. You should take the fuse out of it really, so it can't work, or at least take the remote wire off it.


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## spl152db (Dec 20, 2007)

yea it wouldn't make much sense if there were with the way it acts, but you never know. a punch 900 sounds like one of the newer fused ones.


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## Steve1828 (Sep 6, 2011)

sqshoestring said:


> If it powers up and you have something like 20-30v on the speaker leads, the outputs are toast. Not a bad repair because the power supply is still working at least, it can blow that too. Its better to take wires off the amp then nothing can touch. You should take the fuse out of it really, so it can't work, or at least take the remote wire off it.


So any idea where or who can fix that if it is indeed just that? Or is that something I can do?


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## sqshoestring (Jun 19, 2007)

Any good tech should be able to do it. If you want to try it you can, but if the transistors are soldered down it is a real pain or takes special equipment. If they are screwed/clamped to the sink like most amps you can do it. There could be something else wrong, but it might be just the outputs.


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## spooney (Nov 5, 2010)

If the amp uses the mehsa system for mouting the fets it would be a real pain for a first timer to try and repair. Hell there are some experienced techs out there who aren't all that great at re working them. Find a good shop and get it fixed up. It is not as easy as just replacing the shorted/blown mosfets even if you could get them swapped out. All the driver circuitry would need to be repaired/inspected as well.


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