Electronics Repair Questions? Ask an Electronics Technician
I ll be happy to assist today and thank you for using just answer. The first thing that i would do is look at the pc board from the top and the bottom looking for any lose transistors ,cap,and jumpers also check out the soldering on the pc board.
Ok if everthing checks good check the capacitors in the powersupply make sure they are not blowed up , also you have a 10µf capacitor connected through the diode to the base of the D669A. That and the 1N4004 form a simple half-wave rectifier. The idea here is that, on power down, AC is lost at the transformer, so the 10µf cap discharges very quickly. This pulls down the base of the D669A and opens up the relay contacts pronto. Because of the (sorta) large ripple current across the 10µf cap, it is a prime candidate for replacement.
But again i would keep my eyes on the power supply capacitors.