I am talking about the (Tesla?) R-4 field HF receiver, from 1962. 5
bands, covering 1.5-12.5 MHz in A1-A2-A3, single-quartz filter, 500kHz
calibrator, AC/DC PSU with dynamotor.

I have two of those (I am actually listening to the BBC on 12095kHz on
one of them right now...) but I only have a partial photocopied
manual.

It works well, the schematic is reasonably simple, but mechanically
the unit is a bit of a mess. You can do all the simpler things with a
flat screwdriver, but as soon as soon as I have to take anything
apart, I wonder where to start from and if I'll cause parts to pop out
irretrievably.

Does anyone have a complete service manual for this?

AFAIK, manuals were available in Polish, Czech, Russian, German, and
Hungarian. Spanish and English possible, but I am far from sure. A
photocopy in any language is OK, except Hungarian (sorry).

Thank you for any hints!

Filippo Cattaneo
N1JPR/I2