The Collins R391/URR was made in the 50's. It shares the R390/URR electronic and mechanical design but included an 8 channels mechanical memory.
This receiver stamped N°9 was bought in a very poor state, dusty and lacking the 24V motor. It was said to be functional but it was later found not working.
It quickly appeared that the IF bloc was heavyly modified to use a Collins mechanical filter. Modifications were also made on the AGC path.
This let me think that this receiver was hooked on some kind of TTY equipement. I managed to track part of its history.
It has been sold in the end of the 60's by a German surplus dealer to a French enterprise that later sold it to an ham radio man.
It took some weeks to clean it and made it working:
- the mechnical filted was dead so it has been replaced by three murata ceramic filters without any other major changes in the IF bloc.
- the missing mechnical memory lock stubs have been rebuilt.
- almost all the ajustable capacitors have been changed as the original ones were blocked.