"This belongs to my mate, he says it's crackling, can you have a look?"
Yeah ... why not?
It's a Rockit monitor.
Usual idea, amplifiers (in this case two, one for the tweeter, one for the sub) and transformer/ active cross over all built onto the back panel...
The fault is immediately obvious... the dreaded black goo ... This is some sort of adhesive applied liberally to the pcb to stop the capacitors and other large components "falling out" because they don't trust their soldering (this is a somewhat sarcastic guess, but I fail to see any real reason for it!) It has an issue. After a time, if it's got hot, it can start to conduct, causing undesired operation of the device. I see it quite often.. for example here.
I can see it's got very dry and crusty (and most likely conductive) in a couple of places. Most noticably here ... we'll have to clean it all off to make a reliable repair. The dry stuff mostly chips off....
The rest needs a soak in a bit of acetone (or nail varnish remover), I add a bit to bits of kitchen roll, and allow it to soak in for 30 mins, and the goo just wipes off...
Get as much off as possible.
... and reassemble. Simple fix.
I warned Mike the other one would need doing as well, and cleaned that one up too...
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