Amp/Subwoofer Fuse blew

[FoxClubNiner]

Klipsch ProMedia 5.1 Ultra

The amp was making a humming noise through the speakers when first turned on then would gradually get better. It would do a loud squeak when turned off as well. It's the same thing I've had it repaired 3 times for before. Last week I turned it on and it was making a very loud buzz through the sub woofer speakers (didn't have the other speakers set up yet). I turned it off and it blew the fuse on the amp. I took some pictures of the boards where it seems burnt. Would y'all be able to point me in the right direction for a self repair?

Pictures:
http://s174.photobucket.com/user/DannyGrant_photos/library/

 

[deaedius]

If I see that right it looks like you have a pair of leaky capacitors that may have caused your point of failure. Also you may want to remove the shock from the circuit board unless you plan on taking those Promedia's off road I do not think it is required!

 

[jojo69]

I think the brown goo is just glue to mechanically stabilize the caps

The burnt part is a MOV used to limit inrush current, the 4 legged part it spewed black under is your full wave rectifier bridge.

My guess you have a shorted PSU input transistor.

You have a multimeter?

I'm betting there is some 3 legged stuff on that heatsink between the burnt MOV and the big yellow transformer...check for shorts there.

 

[B00nie]

Be extremely careful when messing with the power supply. You have potentially live mains at exposed pins and risk electricution and/or house fire if you make a mistake.

 

[FoxClubNiner]

I think the brown goo is just glue to mechanically stabilize the caps

The burnt part is a MOV used to limit inrush current, the 4 legged part it spewed black under is your full wave rectifier bridge.

My guess you have a shorted PSU input transistor.

You have a multimeter?

I'm betting there is some 3 legged stuff on that heatsink between the burnt MOV and the big yellow transformer...check for shorts there.

I'm a mechanic. So, I'm comfortable enough to take things apart and kinda see what's going on but I dont really know what does what function. Yes, I have a multimeter. What should I check?

 

[jojo69]

I'm a mechanic. So, I'm comfortable enough to take things apart and kinda see what's going on but I dont really know what does what function. Yes, I have a multimeter. What should I check?

The above comment about safety is, of course, relevant here. Make damn sure the unit is unplugged. then take a screwdriver and short the big capacitors to make sure they are discharged.

My first poke at this would be to check for a shorted switching transistor on the input side. they are under the black spring clips that hold them to the aluminum heatsink between the burnt MOV and the transformer, looks like there are 2 of them.

Flip the board over and find their pins...actually, can you post up a pic of the bottom of that board?