I think your rectifier is bad. The regulator requires at least 7 Vdc at its input (and because the input is unregulated, it should be 7 Vdc at 103.5 Vac line power input, else a line regulation check would fail, and at least 7.8 Vdc with 115 Vac line power input). What is the Vac across C22? The ripple usually goes up with failing rectifiers. (The rectifier is a hard working part, continuously turning on and off with relatively high forward current.) I'd also check those electrolytic capacitors.
Also, the input to these regulators normally have what may seem to be a lot of ripple, which the regulator must take out. (They may work with a lower input voltage if the input voltage is smooth with relative little ripple, such as from a lab supply.) Read the datasheet for your regulator. Most passive regulators I've seen want 2 or 2.1 Vdc more voltage at the input than the output. I've replaced several rectifiers due to low voltage at the regulator. (And I want to know if the unit will work at its lower power line voltage specification, which can be directly tested using a Variac.)