Something different this time. This is a Yamaha drum machine. According to the board stamp it's circa 2003/04. My first thought was how did this platicky toy have survive this long but be that as it may, this is a Yamaha you know. Any Yamaha made anywhere will guarantee to surpassed any Wang Hung Low electronics appliance.
The problem of this DD-55 was according to the owner is "cikgu,sound dia semput bila kita ketuk kuat" which roughly translate to "hitting it hard causes surging sound from the house speakers.
At first heard the fault sounded like a less amperage generic adapter was used with this DD-55. Upon checking the adapter is indeed legitimately stock so no problem there.
From the enclosure screws I could tell someone else had been in there before. There's seems to be a handful wrong size and length screws mixed with the stocks.
I have to admit I was mildly pissed by this as there were screws at spots that never needed it. For that I have to advise you Macgyver out there that should you want to dissemble any appliance. Count the screws and put a mark them to the spot that it should belong. Failing could result breaking the enclosure or even the PCB inside.
Coming back to the DD-55. While testing and noticing the audible flaw, I can't help to realise that I stumble with this same problem before. Upon checking I notice the filter cap solder pads look not convincingly firm compared to the surrounding pads. A couple of renewed lead solved it. It was indeed a couple of dry joint. To see an example of a dry joint click here