I miss being on the air on HF. It's been almost a year since my radio died. Many other competing priorities have intervened over the past year, but I can see the light at the end of the tunnel.
I started hanging around the ##hamradio channel on IRC, and discussed my TS-520 woes. A couple of the guys on there who have owned Kenwood hybrids said that it sounded like the power transformer gave out with an internal short. I haven't actually diagnosed it yet, as that would entail fully isolating the transformer and then checking the voltages under no load. It could be a couple other things (AC to DC capacitors, some resistors, etc).
I found a guy on swap.qth.com who was parting out a TS-520 that powered up. (Hey, that's better than mine!) So, I bought from him the power transformer, the power cord, and the door that covers the adjustment pots on the left side of the radio (since mine was missing when I bought it).
I plan on keeping the nicer of the two power cords, and using the plug from the remaining cord to wire up a DC power cord.
Shortly after the radio died, I also picked up a complete capacitor replacement kit and a finals resistor kit from hybridrestore.com - and I might tackle that at some point. I think I would need to beg/borrow/buy a decent soldering station, though; my 30-watt soldering pencil has proven itself a little underpowered for some of the solder joints in this radio, and my butane soldering iron is, well, a little overpowered. It's only 50 capacitors; should only take me about 7 weekends or so. :)
On that note, I hope to be back soon with update on my repair progress.
73, K9MJA
