I acquired this set with a blown HOT and power supply, and presumably a bad flyback as well. I replaced the flyback, HOT, and a number of power supply components including the MX0841 IC. Wouldn't you know it, I had missed a shorted zener in the power supply, and of course blew the brand new switching IC. Since I didn't have another IC in stock, and it appears to be nothing more than two switching transistors in one package, I tried replacing them with a pair of normal switching transistors, similar to those used in other Sony power supplies. This was of course after removing the shorted zener diode from the secondary side. The power supply now starts but the voltages are very low. There are three supplies on the secondary side of this switching transformer (a separate xfrmr & circuit is used for the 5V standby); the B+, which measures at just 50V, a 12V supply which measures at 3V, and a 9V supply which is at zero. Removing the
12 and 9 volt rectifiers brought the B+ up to about 100V, but the power supply makes a noticeable squeal and sounds like it's either straining itself or not running hard enough (the switching transistors don't seem to be getting warm though). I've gone through the power supply and can't find any bad resistors or diodes, which leaves me with just one question: is the problem related to my subbing the MX0841 IC, or is there something else wrong with this power supply? This is a difficult circuit to troubleshoot and I'm just afraid there might be something more serious at fault. Thanks for any help.- posted
16 years ago