NR5P:
I had the same inspiration last december and I purchased a working Collins first series R392 with a Switching PS and LS166 from an italian ham for 400Euro.
I am very happy with it. After some minor electrical fixes I will repaint the box and will use it.
Manuals (BAMA) are made for servicing, just follow them.
My R392 is full tube, no transistor and no semiconductor diode.
I discarded the switching PSU (because of RFI) and built a linear PSU with 26V 4A current limited, this PSU has a 30V zener+SCR overvoltage limiter after a 4A fuse.
4A are not enough for filament current surge. The PSU takes 20 seconds for exiting the current limit of 4A, after this warm up phase, the PSU works fine (and filaments are not stressed at power on...).
Changed two or three 26A6 (IF and RF) for some gain in s-meter reading, previously installed tubes worked fine indeed.
Increased the BFO coupling capacitor with a 68pF in parallel to C618. Now I do not need to reduce the RF gain in SSB-CW. After this mod, retune T601 for maximum audio output - T601 does not affect the S-meter.
Follow the manual on how to remove the lower deck (very easy - set BW to 8 kHz, few connectors, green screws and lift).
Fixed overshoots of ALC in SSB with a 20k trimmer resistor in series to C103 (this capacitor is on the front panel near the BFO switch - very easy to access)..... In 1950 they apparently had no idea of pole-zero compensation in control systems.
I added a trimmer to the cathode of one of the IF tubes in order to follow the schematic of the second series. (the first and second series also differ in the number of slugs in the RF coils - see the two manuals available on the internet).
Reduced the ALC operation on first RF amp 26A6 with a 1 Megaohm resistor wrapped on test point E201 near V201 and ground. This mod increases sensitivity and improves ALC dynamics in SSB.
The receiver may require touch-up alignment (if it already works)...
Read this if needed:
http://www.antiqueradios.com/forums/viewtopic.php?t=58404The receiver is very sensitive on any band. I can receive BC without any antenna (the antenna is the antenna connector). I never perceived intermodulation by tuning BC bands, or 40m Ham near BC edge, or MW, using SW full size dipoles.
Audio quality in AM is very high, much better than most receivers I have, if using a wide band loudspeaker. I have found a 600 ohm dual cone speaker made by Philips in the '60.
Frequency stability is surprisingly high.
The R392 is a masterpiece, no doubt.
Tubes are here:
http://stores.ebay.com/K5SVC/TUBES-/_i.html?_nkw=26&_fsub=8&_sid=14089412&_trksid=p4634.c0.m322Giorgio