Broken Soundstream MC Amps

I have two non-functioning Soundstream MC amps. I don't know the history on either amp.


MC120
No lights when powered up.
Power supply setup is 13.0 volts.
On startup after about two seconds, the voltage 7.3 volts and the amp draw is 9.0.

MC140
No lights when powered up.
Power supply setup is 13.0 volts.
On startup after about two seconds, the voltage 13 volts and the amp draw is 0.0.

Any help will be appreciated.
 

jol50

Member
2007-11-08 2:14 am
Pop the cover and take an ohm meter, test all the transistors on the heatsink. I do the outside legs, any shorted will tell you a problem is there. There may be two that are shorted, those would be rectifiers and go to rail caps. If the rest test high ohms then check outside to center legs. Look closely for any soot or burns, melted solders, etc. If you are not sure what to look for go to Perry's site and check it out: http://www.bcae1.com/ Wild guess is the one that is dead has a power supply fault maybe turn on circuit, the other one output section is damaged. Take the one that runs and check voltage at speaker leads when you fire it up, briefly. Check each channel for DC voltage and bridged channel. That might give an idea what is wrong. I have not worked on one of those. If you have lights that do not light you may have a secondary power issue, the power for input section.
 
More info:

MC120
No lights when powered up.
Power supply setup is 13.0 volts.
On startup after about two seconds, the voltage 7.3 volts and the amp draw is 9.0.

The previous owner had had replaced one of the 3 amp fuses with a 10 amp and run that side in mono. The two dark blue 2200uf25v caps on that side are leaking. The main fuse was changed to 25 amp from what I think should be a 20 amp.



MC140
No lights when powered up.
Power supply setup is 13.0 volts.
On startup after about two seconds, the voltage 13 volts and the amp draw is 0.0.

Couldn't see anything wrong. Everything looked brand new inside.
 
The caps need to be replaced. While you have them out, THOROUGHLY clean the board and check for open traces. The electrolyte is corrosive and will eat through the copper foil. An open trace can cause excessive current draw. It's also possible that one of the caps is shorted.

Did you check for shorted rectifiers or shorted outputs?

Did you check for supply voltage on the MC140?