I’m very happy to report that thanks to a NOS pair of Eimac 4-125A modulator tubes from Antique Electronic Supply, my T-368C is back on the air for the first time since I got it! I’ll still have plenty of tinkering to enjoy on it, and plenty of work integrating it into a full system with my R-390A receiver. I’m also happy that my antenna BALUN didn’t burst into flame upon encountering the hefty output of this small monster of a transmitter.
My T-368C transmitter uses three impressively large transmitting tubes. The power amplifier (PA) uses an Eimac 4-400A, while the modulator uses a pair of Eimac 4-125A tubes. These big tubes are beautiful in my opinion, especially when they’re operating with the plates glowing red. Sadly, they’re not normally visible in operation due to the transmitter’s opaque steel cabinet, studded with interlocks to keep folks away from the lethal high voltage that lurks inside. Even with the interlocks bypassed for debugging purposes (which is dangerous, and should be avoided when possible!), the big 4-400A tube is further obscured by an opaque metal chimney which ducts cooling air around it.
I’ve made some good progress on my T-368C transmitter already. The arcing problems have subsided on their own, though they may come back later. I traced down the modulator problem to a single resistor in the speech amplifier which failed open, thus removing power to the clipper tube’s plates and breaking the audio path. The transmitter is now working on CW and AM at full power into a dummy load! I also replaced another resistor in the same speech amplifier circuit, but I think it was actually OK and I just had a measurement error due to residual charge in the circuit.
There are still some kinks to work out…
I bought a T-368C HF transmitter project back in October, 2007 for $1575.42, and finally started seriously working on it a couple months or so ago. This evening, it got its first taste of power in many years! It’s semi-alive, but needs more work:
A collector who just bought a Fialka cipher machine asked me how to load the paper tape, which is tricky until you’ve done it a few times. Here’s how I load the wide paper tape (for printing and/or punching) into my Czechoslovakian M-125-3 machine. His machine is a Polish M-125, but hopefully the paper path is about the same (I’ve never handled the earlier model of Fialka, so I’m not sure about that). The paper tape path is a bit different when using the narrower print-only paper tape, but I don’t have any to demonstrate with.
The SCR-619 radio set could be deployed in several different configurations, including vehicular and man-portable. In a man-portable configuration, the BC-1335 transceiver and CH-191 battery box would be installed on a common pack frame with an FT-505 mount. These mounts seem to be quite rare, as I’ve only found about two or three collectors who have them or have ever seen one for sale. A few months before the 2010 West Coast Military Radio Collector’s Group annual meeting, Paul Thekan kindly loaned me his FT-505 so that I could photograph it, measure it, and display it with my SCR-619 set at the meeting. I didn’t just photograph it, though… I also created a 3D CAD model of it, with thoughts of someday fabricating a reproduction.
I have had a static web page for many years, but I’ve just moved it over to a WordPress-based blog. The new format adds many features such as searching, tags, comments, and an RSS feed. I’ve ported over most of the content from my old web page with minor reformatting and revisions, and I maintained the original publishing date stamps for the old content. I may also go back and plug in things like pictures of past events that I never bothered to share before, so please forgive me for engaging in a little bit of revisionist history.
I hope that y’all like the new format!
The “Fialka” is a cipher machine which was made and used by the USSR during the Cold War. I found this one on eBay, and it only required minor repairs to become fully operational. I’ll write more detailed information about it later; in the mean time, here are some pictures of my Fialka. You can also find more details about this kind of machine on Wikipedia.
The Hagelin CX-52 cipher machine which works on the same principal as the M-209 Converter. I’ll write a more detailed description later; for now, here are some pictures of my CX-52 that I found on eBay, along with some details about how I cleaned up and repaired it.
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