A completely reverseable LED lighting modification was done to improve the dial lighting. Receiver aquired from an estate a few years ago in very nice shape with matching rare speaker 312B-3. Collins 51S-1 receiver with match spkr I have a Collins 51S-1 W.E.
- Submissions r-39-qth.netAlso, FYI, I had one dead filament on half of my 6082 - only three of the four triodes lit up. So, there are readily available over-the-counter transformers available that'll work with the '390 and other 600 ohm output rigs. In practice, this is very difficult to achieve with antennas and transmission lines, particularly when they have to work over a wide frequency range such as 2 to 30 mc.My second 390 was 99% stock - I replaced the 26Z5's with soid-state diodes, and the selenium rectifier for the 28 v DC relay supply - it's that little round thing in the power supply.The closest tap to 600 ohms was 500, so it wasn't a perfect match, but close enough. Original Collins Noise Blanker KWM-1 KWM-2 75A-4 75S-1 Receivers DISCUSSION 25.00 Collins 75S-3B/3C Amateur Ham Radio Receivers Orig Owners Manual & SchematicIf a 600-ohm load is connected across the 450-ohm·output of this device, a standing-wave ratio (SWR) of 1.33:1 (600/450) will exist, assuming a balanced input and output condition. Did that years ago on my first 390. Or you'll have a pile of junk on your hands.
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Not to mention that it is a completely different critter inside. IMHO the 390A is almost as good, but it doesn't have the audio filter or the SQUELCH function.
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