Working on a cheap amp.
Switch Mode Power Supply had some issues.
It had a blown power mosfet that drives the primary winding. Also blown Schotkey on the secondary side. Replaced those.
Did the 100 watt light bulb across the fuse holder trick. Light lights then dims and goes out withing perhaps 4 seconds. Removed bulb and replaced with proper fuse (6.3amps 250V BTW I am In America so we have 120VAC 60HZ mains). Old fuse was way too big value and size wise. Did not even fit right :(
I have a blue Ring Tester and it said the Transformer was good both in and out of circuit. When I try to power up with no load on the + and - 60 volts the SMPS chip that drives the mosfet gets 7 volts on the shutdown pin and nothing happens. I expect that is normal with no load.
If I connect the main amplifier power board the same thing happens. Shutdown. If I connect a 100 watt Light bulb across the + and - 60 I blow both fuses and the NTC. Replaced all that. I couldn't really get my clips onto just one side of the power. Suppose I need to solder in a resistor but I don;t think I have one big enough with the right wattage. Perhaps I am not using a proper light bulb for the load? Supposed to be 600 watt 9 channels. Makes it about 75 watts per channel?
Anyone got advice what to try for a dummy load? What Ohms etc? I think the SMPS is working right but the original load is somehow open and maybe the light bulb is too much for the amp. What do you folks think?