[Heathkit] HR-1680 Documentation ?

[n3aaz_qrp_1 at juno.com]

Is there any more HR-1680 documentation out there?
Nostalgic, I dusted off my HR-1680/HX-1681, built in 1977, both still work ! ! !
Googled and found "Bulletin No:HR-1680-1 thru -20" dated Nov-76 thru Oct-92 and
 lQQking for additional information such as mods es/or service notes.
After many years I have overlooked what a pleasure it is to listen to an ‘analog’ (verses ‘compurized’) radio.
TNX
John
N3AAZ