I've been looking at one of these for a friend, and I found this video:-
Basically the +/- 15 V supplies are regulated from the +/- 55 V, and lots of heat is dissipated in the regulators and some series resistors, which get too hot and are damaged, burn the board or give poor solder joints.
The manufacturer has obviously realised that there's a problem, and the one that I'm working on is newer, has different resistor values, and they are mounted remotely on the heat sink.
I found the circuit diagram here:- masterelectronicsrepair.blogspot.com/2019/02/kef-psw-2500-powered-sub-woofer.html but the one I'm looking at isn't quite the same. Here is the circuit of its power supply that I have modified to match the PSW2500 that I have here:-
The 270 Ohm resistors are the white, square section ones that are mounted remotely.
The question I have is about the 2.2k resistors. They are 2W rated, and have discoloured, and some have come loose. Obviously the two that are before the 270 Ohm resistors are worse. They are right beside the 12000 uF capacitors.
What is the function of the 2.2 kOhm resistors? Could I just remove them?
BTW, before anyone asks, the main capacitors are bulging at both ends, and they feel like something is loose inside and they will be replaced. Oddly, the capacitance is about right. I can't measure their ESR.
Basically the +/- 15 V supplies are regulated from the +/- 55 V, and lots of heat is dissipated in the regulators and some series resistors, which get too hot and are damaged, burn the board or give poor solder joints.
The manufacturer has obviously realised that there's a problem, and the one that I'm working on is newer, has different resistor values, and they are mounted remotely on the heat sink.
I found the circuit diagram here:- masterelectronicsrepair.blogspot.com/2019/02/kef-psw-2500-powered-sub-woofer.html but the one I'm looking at isn't quite the same. Here is the circuit of its power supply that I have modified to match the PSW2500 that I have here:-
The 270 Ohm resistors are the white, square section ones that are mounted remotely.
The question I have is about the 2.2k resistors. They are 2W rated, and have discoloured, and some have come loose. Obviously the two that are before the 270 Ohm resistors are worse. They are right beside the 12000 uF capacitors.
What is the function of the 2.2 kOhm resistors? Could I just remove them?
BTW, before anyone asks, the main capacitors are bulging at both ends, and they feel like something is loose inside and they will be replaced. Oddly, the capacitance is about right. I can't measure their ESR.