You need more testing of those transistors. You've shown that they are capable of being "off" and that there is a BC junction, but have not tested the BE junction nor confirmed that they are capable of being "on."

The most likely layout (I can only guess, as I don't have a schematic) is that the output of the 723 goes to both 3055 bases, the 3055 collectors are connected to the "bulk dc" line, and the 3055 emitters each go through a low-ohm high-watt resistor (likely R13 and R15), the other ends of those resistors being connected to the output.

My guess is that either the 3055s are bad (failed open-circuit, ie, they never turn "on") OR they are not seeing sufficient DC on their collectors. I'm imagining that the 24V you DO see is being realized by the output of the 723 passing through the base/emitter junctions and resistors to reach the output. This means you're overloading the 723 (throwing it into current limit). Also, if the 723 were able to provide enough power, you'd end up further destroying the 3055s anyway.

My prescription is to replace both 2N3055s. They're dirt-cheap NPN BJTs. If the power supply is built the way I think it is, you should actually be able to substitute in just about any transistor having similar (or higher) power and voltage ratings. Before anybody questions me on that, I know the gain could sorta matter, but since the 3055 sucks so bad, anything modern is going to be the same or higher. smile