EricM wrote:

BTW, what is connectors 2 on CR4 and CR5?
Does somebody switch from 8 to 2 at some point?

The 1N1239 was a replacement for the
5R4 vacuum tube rectifier;

Oh, that explains it. Then the 5R4 ist a directly heated rectifier
tube and the 5 Volts AC are the heater power. This is, you may
disconnect 12 and 13 from the mains transformer when using
selenium or other semiconductor rectifiers.

I also located another online vendor that
sells 'C-Cap' rectifier replacements and he states that his 5R4
replacement should work. I'm debating whether or not to order some to
test though,

Investments into faulty equipment mostly turn out wrong, if a sound
reason for the purchase is not present :-).

And essentially what the relay does, is shunt resistor R5,

To give the amp tubes time to heat up before anode etc power is
applied. Very reasonable.

as pins 2
and 8 seem to be looped no matter what position the relay is in. This
one is really a pain - I've never encountered a PS like this one...

It looks quite ok once we understand everything :-).

Now, once the power supply seems to be ok, I would follow the 600 V
wiring into the amp with an Ohm-Meter and try to locate a low
resitance to ground.
Next I would check all anode-to-grid caps like eg C19 at V8b. If some
of those leak, the grid will not be negative enough and anode current
will go through the roof.
I'd disconnect T2 on the primary side and measure the resistance of
the windings and the resistance to ground, to prove that the
transformer is still ok.

Well, much everything like in a common radio repair :-).

Regards,
H.