Monitor Audio Rs Series Service Manual
So I got one these second hand. It was sold as having a hum which settled down to barely noticeable after a few minutes.
It turned out that was putting it mildly and the thing rapidly deteriorated. I was aware that they had a very high failure rate on just this issue when I got it. What surprised me was that there were so many people reporting the issue on various forums but I couldn't find anyone reporting what caused the fault and how to fix it. I've just got mine back from my tech, who is very very good, and he's filled me in so I thought I'd share the knowledge. That way, hopefully the other owners googling their issue will be able to find something useful and repair.
My tech does not like class-D, and I warned him this one was likely to be a shocker. He tells me that in terms of both design and construction, given that it's a cheap(ish) class-D built by a non-amp manufacturer, it's actually not that bad. The problem it seems is that it's a sealed sub and contains secondary components (such as the VRMs) which generate heat inside the sealed box.
This leads to a thermal build up which fries the caps. Mine had around 7 electrolytic and 2 ceramic caps replaced with uprated ones more able to handle the rough operating environment and a slightly melted wiring loom replaced. Mine is working perfectly with no hum now so that would seem to be the ticket for restoration.
I'd also recommend fully powering down when not in use, both to prevent thermal build-up damaging the caps and, given the melted wiring loom, possibly to avoid a potential fire hazard. That along with replaced and uprated caps ought to keep them running for many years. Hope that's helpful for someone out there. FYI, Monitor Audio are very helpful and can email schematics of the RSW12 Circuit, but have no knowledge of component level repair. The 4700uf 80v only run at 54 volts in the UK (242 Volts at my house), so I just replaced my friends with 6800uf 63v Elna from Maplin as well as replacing every other electrolytic with Panasonic equivalents. There are about 15 to replace in total and costs about £20 in all. The original Caps are made by Jun Fu, obviously a reputable brand.
There is a back gunky bitumen type stuff all over the wiring loom which is there to stop the loom and ferrites rattling. It looks burnt, but isn't. Incidentally at the end of June 2016, Monitor Audio are releasing a 3rd Generation Class D Retro Fit amp for the RSW12, which is based on the Silver Sub Amp and will come with a new top control pad for volume and EQ, but will not have the microphone Function. It will be £200 delivered (I doubt to Australia though, unless the dealer can help) and is claimed to be better sounding than the older Amp.
Mine had developed exactly the same symptoms after 10 years of use. It is open on the work bench now, and the obvious candidate is a pair of 400uf 80V filter electrolytics showing obvious signs of drying out. There are also signs of heat stress with lots of melted cable wrap to be cleaned up.
Monitor Audio Rs Series Service Manual Free Download
I'd replace all of the electrolytics if I were you. The smaller they are the more susceptible to drying out.
It's not like they cost a lot and even if they've not failed now it seems like sensible preventative maintenance.
Monitor Audio Rs Series Service Manual
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