Expert electronics opinions needed: Radiola 60

[Kamakiri]

I'm working on an RCA Radiola 60. This is gonna get good, so follow along and put on your thinking caps

The Radiola 60 was the first AC powered radio made, and has a split chassis....one side of the chassis is the radio itself, and the second is referred to as the SPU (Socket Power Unit). Diagram of the unit is below.....RCA wasn't very forthcoming in any of the service literature as to part values, as they didn't want any small companies stealing their patents. I was able to verify the values of everything so far, though.

Here's the issue

After fiddling with the radio forever, changing tubes and doing the center tapped 1 uF and dual .5 uF caps in the radio unit, I was able to get just one station on the radio, 550 AM. If I power up the radio after it sits for a few minutes, it comes in with a decent audio level, but quickly sags to barely audible. Obviously I have alignment issues, as I used my signal generator up the AM band and by the time it hits 1000 KC you can barely hear it at all.....but one thing at a time.

The diagnosis and repairs

Tested the resistors in the SPU, everything looked good. As you can see in one of the attached diagrams, the SPU is connected to the radio with a terminal strip.

The book shows voltages as follows:

Terminals 1 to 7 - 200 VDC (I have about 135)
Terminals 2 to 7 - 210 VDC (I have about 160)
Terminals 3 to 7 - 160 VDC (I honestly don't remember)
Terminals 4 to 7 - 110 VDC (same....)
Terminals 8 to 9 - 5 VAC (spot on)
Terminals 10 to 11 - 2.25 VAC (spot on)

To begin with, I dug out all of the beeswax and replaced the capacitor network inside the one can (they tested good, but given the issue I wanted to make sure to start fresh there). No change.

Then, I went through the tests shown and the only one that failed was an open across the G to P (small pins) contacts of the 80 socket....showing an open high voltage winding of the power transformer. Apparently this is a common issue on these, and from what I can find this is the end result.

Question #1: Am I barking up the correct tree?

If I am, then I have an unorthodox idea for a replacement that I think will work......

I've also attached a diagram of the power supply in an average radio powered by a 5Y3. If I were to use the 5Y3 in place of the 80 along with that transformer, choke, and cap network.....would I be able to use that out of a junk radio if I had a resistor network to get the voltages correct? Shows 280 VDC on pins 2 and 8 of the 5Y3 in this diagram, and I could drop that down with wirewounds. Basically, build my own custom SPU......or, is there a known better replacement instead?

Your ideas and thoughts are appreciated!!