Welling HS-8 Powered subwoofer problem..

[dan.murray]

Hi everyone,
I am currently attempting to give new life to a forgotten powered sub. When i first turned it on it made a very loud "HUM" and then the fuse popped. I found the cause of this to be a shorted C2837 (Sanken). I replaced the transistor pair (C2837/A1186) and the hum went away and fuses stopped popping. The issue now is that the system only amplifies for short periods of time at what seem to be regular intervals. i.e. without any input, there is a small "pop" at a rate of about 0.5Hz. When I do connect an input, it will be amplified for the duration of that pop, so if you can imagine every two seconds or so, the song comes on for about 1/4 to 1/2 of a second.

I have never come across anything like this before, has anyone got any information to point me in the right direction?

Thanks in advance.