I can second that, the eastern electronic was never 'sexy' and almost never 'state of the art', but they built this to last forever (no intention to sell more by creating obsolescence). If you look at the schematic, you will maybe recognize the germanium* based transistors. The most actual components seems to be the rectifier diodes, that can be translated to D15 or such. Its almost 50 year old (from the early 70s) and by western standard the style of the 60s. You can see the typical rectifier and regulator schematic, as if directly taken from the book, carefully choosen component values with enougth headroom to operate.
I miss this style today: rock solid devices, you can always(!) count on. Today you can only get devices that runs on the maximum ratings and the only choose you have is how much after market service you want to buy. (for extra fee.).
There is even a list of the components and their manufacturers. The transformer is made by Straton himself. They seems to know what they do.
You should'nt buy this two devices, but you can study the schematics. There is even a description of the way this circuits works (google can help with translation). See how they crafted this design, look at the semics and the used window in the characterics, rebuild this in Spice and play with the component values. You can learn a dying art: 'how to design rock solid electronics'. Something that isn't teached at universities. Something that should be teached. IHMO its one of the key differents between a ordinary 'BoA paper owner' you could hire by dozens and an excellent engenieer that can build the well-known qualities 'Made in USA' or in ths case: 'Made in Germany'.
Thanks for sharing this look inside.
Greetings
Bernie
*a german electronic device made of germanium semiconductor. Pun intended?