BK Electronics Amplifier Repairs
BK Electronics MXF200 MOSFET Amplifier
This one was buzzing on one channel, looking inside showed the main capacitors were u\s 4700 µf 63V.
BK Electronics MF300 MOSFET Module
This is an old power amplifier from the 1980's, before using it I thought it would be a good idea to give it a check out. The MOSFET's were removed and the heat-sink compound replaced. The TO126 transistors which are riveted on to the heat-sinks were checked for tightness, some were loose. The original capacitors 10000 µF 80V were replaced with modern smaller ones. I decided to replace the main caps with more up to date ones, made an 'interface' board to support them. There is a solder link to check the quiescent current, it should be about 60-80 mA. Sounded okay at switch on.
BK Electronics MF300 MOSFET Module
Another MF300 for repair. This was blowing the two fuses, the 2SA872 used as a current source was s\c, the green LED was open circuit and the 1k2 resistor was burnt, replacing these got it working again. Thankfully all the MOSFET's were okay.