I ended up buying one of these off of eBay. The seller listed it For Parts/Repair" and said it wouldn't power up, not a surprise, since the fuse holder was missing.
When I received it, I opened it up for inspection. Mine seems to date to the mid 1980s. I haven't tried powering it up yet because I found some issues during my preliminary inspection.
First, I noticed that the PCB under some of the components has started to discolor from excessive heat. I wonder if anyone else has seen anything similar? The specific components implicated in my unit are some diodes at E22 & E23, a heatsinked 5V VRM (mc7805CK), a big power resistor and a less beefy resistor.
The other issue is there are two components at the back right of the main PCB. I think they are decoupling caps with a connection to the chassis, though the markings confuse me a bit. A lead has torn loose from one of them, and neither of them are securely mounted.
One hypothesis is that they are 0.2uF axial caps rated to 5000v, made in 1974 and 1975, probably bodged in as a repair. My confusion comes from what I take to be the older of the two using the newer uF designation, and the newer using an older 0.2M designation. The other, is that I have no idea what they are. Can someone validate either of my hypothesis or suggest alternatives?
This question would be easier to answer if I had a service manual, but as has been noted, the one available online has the diagrams and parts lists cropped off to a letter sized page. If anyone has a better scan, or can point at a reliable source to buy a reasonably priced manual, that would be appreciated.