John,
I don"t know which came first - the Heathkit HD 3030 or thr Flesher TU-470.
But they are absolutely identical to the extent that I took the power
transformer out of a dead TU-470 and put it in an otherwise good Heathkit.
It worked perfectly. Both have internal loop supplies.
Note: these old TU's don't like today's line voltages. That is how
the transformers burn out. I have to run them on an eBay bucking
transformer. They are very happy that way. My FlesherTU-170
runs noticeably cooler too. The bucking transformer was well
worth the 90-some dollars.
Tom N3CRK