> The root cause of the failure appears to be that the internal voltage > reference of the uA723, which is specified as 7.15V ±0.35V, is now > 9.4V. The uA723 needs to be replaced. The uA723 is still readily
That's an unsual failure. I've had 723s go internally short-circuit and then the output voltage is essentially the input voltage, but never seen the reference drift. > available, but due to the construction of the power supply, replacing > it is relatively difficult. Just probing the pins of the chip was a > challenge. The pass transistors are mounted to 1/8 inch aluminum > plate, but the pins are soldered into rivets in the single-sided PCB, Ouch, that sounds horrible to work on. One thing... I had a (SMPSU) that seemed impossible to work on, it was built a bit like that. Then I found that those 'rivets' were actually sockets and the transistors were plugged in, not soldered. All I had to do was unto the mounting screws and it all unplugged. Of course I didn't realise this and spent some time desoldering things. I assume you have proved your pass transistors are soldered in place. -tony