On our way to a family Christmas party, I found an envelope full of capacitors and a small box containing a wonderful condition 50C5 vacuum tube. Woo hoo!
On my return to the shack tonight, I heated up my soldering gun and replaced that final capacitor (the cap was a .015 uf 400v cap, but I put in a .022 uf 600v capacitor … I had to buy 10 of the things on eBay, but that was OK. See, the capacitor values on these All American Five radios are very generic; all manufacturers pretty much used the same values.
The 50C5 arrived looking as good as new, which tickled me to death. After I unsoldered the cap and installed the new one, I put in the missing tube. Rather than put the radio back together, I decided to hook it up with the cheater cord in order to see the filaments light up … if they did decide to work.
I turned the volume control until it *clicked* on, and waited. The tubes began glowing (no smoke, so that's good, hi!). No hum, no static, no noises, either. Hmm ….
Suddenly, the speaker came alive with stations, with what had to be the best sounding tube-type AM radio audio I've heard in recent years. It was so unusual to hear a tube radio operate without ANY hum …
I'm jazzed, to say the least! These radios are simple, and my next stop is to do a similar recap refurb on the other similar All-American Five radios in the house. I think I have three or four, though I'm not certain if they all absolutely need recapping. Probably not a bad investment, eh?
The parts were cheap enough, and the next time I'll buy more than just two electrolytics (they're really cheap!). I also have a couple of bigger projects to consider … a Hammarlund HQ-110 I picked up eBay several years ago doesn't work, and needs to be repaired (or at least a little troubleshooting); I also own a fairly rare Hammarlund RBG-2, which is a military version of the HQ-120 single-conversion receiver. This receiver will need some special attention, as it has been hacked up pretty hard. It DID play, however — once I jury-rigged it. Let me explain….
I got the RBG-2 receiver about 35 years ago from a guy in LaRue County who tweaked and repaired my family's CB radios. We were visiting him once for a repair, and I saw this behemoth — the RBG-2 — under his workbench. I asked about it, and he told me it was an old military receiver. I think we gave $20 for it, untested.
I got it home and found a odd-value resister; I replaced it with a Franken-resistor that added resistance from 5 different resisters. Good use of resources, sure, but it still didn't work.While I had the receiver opened up, I noticed if I touched the chassis of the RF tuned circuit sections with a screwdriver, the speaker came alive with signals! I experimented a while, and found that if I connected my antenna directly to the tuned circuit coils of each band that the receiver worked great guns; I was more interested in using it than repairing its deficiency at the time, so I built a bandswitch box and wired it to the tune circuits. This allowed me to switch the antenna externally to the “correct” tuned circuit every time I changed bands. It made the old boat anchor come alive, and I used it that way for many years (the switchbox, built from a cheapie Rad Shack project box, had to be cut loose after it was damaged beyond repair during a move).
In looking at a schematic (which I didn't have then, but have now), what I did was to bypass the first RF amplification stage, which fed the amplified RF from the antenna to the tuned circuits. Why this stage wasn't working could be as simple as a bad tube or open wiring; I never investigated it (I never had a manual or schematic).
I did locate one once; I placed a free “help needed” line ad in one of the electronics magazines of the day; I received a letter from a guy who would sell me a reproduction manual. I never took time to buy it, I was too busy using the receiver.
The receiver is out in my garage, and I would love to go through it and get it playing again. It's not in bad shape to be a war-surplus Navy workhorse; I remember taking it to Scott Gordon's house where we took it out of the cabinet and resprayed the cabinet (but not the front panel). He had a Hallicrafters SX-28, which I have always wanted to own myself. Maybe some day … hi!
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