amp has 52 volts to woofer.

[fisherdan]

hi all!
i have a subwoofer amp that when pluged in and not hooked up to a reciver makes the driver extend as far as it can out, then the fuse blows after about 6 or 10 seconds.
i got my volt meter out and it reads 52 volts going to the driver.. dosnt matter if its on or off.
ive never messed with one of theese befor, but im thinking the amp is shot. i just thought i would see if there are any ideas befor i toss it.

 

[Haoleb]

Something is definetly wrong with it, I dont know if its worth chucking or not but it certainly will need repair to be used again. Without having the amp in front of me I cant tell you where to look specifically for the problem. It could be many things. One of the most probable is blown output transistors.

 

[fisherdan]

hmm.. maby ill keep it hangin aroun in the garage for a while.

i also have another subwoofer m&k longthrow 200watt and the driver barrly moves. i even turned down all the other speakers and turned the bass and sub to max then cranked my volume all the way up. and still it just kinda wiggles a bit and very little noise comes from it.
i am sure that its not the signal going into it as i swaped it out for another sub and that works fine. i also swaped the driver and is works great with a different amp.
was kinda hopping that it a easy fix power supply maby?
any ideas?

 

[Haoleb]

Its hard to say what could be wrong with your other sub without an experienced tech looking at it. Sometimes products will have a common problem with the same components failing, you may want to try contacting M&K and see if they can tell you anything. As far as I know they were out of business for a while but are now back, there might be someone who knows that model.

 

[yettitheman]

Holy crap! 52 VAC????

My PhD will say "something isn't right"

 

[fisherdan]

lol yea, and its not AC its DC. i have a old jbl amp that has 87 volts dc at the amp, and it does the same thing, pushes the woofer out REALLY FARE and then hums for about 5 seconds then POP goes the fuse.

and yea i shoud try to get M&K on the horn and see what they say.
thanks again!

 

[mtrycrafts]

lol yea, and its not AC its DC. i have a old jbl amp that has 87 volts dc at the amp, and it does the same thing, pushes the woofer out REALLY FARE and then hums for about 5 seconds then POP goes the fuse.

and yea i shoud try to get M&K on the horn and see what they say.
thanks again!

Bad caps perhaps that should stop DC from getting to the sub or certainly other failed part. You should have next to nothing going out with no signal.
Lucky you are not frying the voice coils.

 

[croseiv]

It's a wonder the coil's not frying!

 

[fisherdan]

i did fry 1 coil, thats what made me get the volt meter and do all the testing!! lol untill i get to the bottom of this ill be using my cheep sony driver. just in case.
and yes i tested my good amp and it get nothing with no signal going to it.

 

[TLS Guy]

hi all!
i have a subwoofer amp that when pluged in and not hooked up to a reciver makes the driver extend as far as it can out, then the fuse blows after about 6 or 10 seconds.
i got my volt meter out and it reads 52 volts going to the driver.. dosnt matter if its on or off.
ive never messed with one of theese befor, but im thinking the amp is shot. i just thought i would see if there are any ideas befor i toss it.

One or both of the output transistors has failed. Power transistors usually fail in short circuit mode. If it is a poorly designed amp, there is no speaker protection and the rail voltage is delivered to the speaker voice coil and fries it.

I strongly recommend against using am amp that can alow this to happen, so I would not fix that amp.

 

[fisherdan]

thanks for the dead on answer.. and the advise about not fixing them. ill keep that in mind when buying a new amp.