Love this. When I was a kid, my friend and I used to visit radio and TV stores to scrounge old radio chasses just like this. We take them home, not to repair them, but to scavenge them for the parts. We'd use these big ass soldering irons or guns to remove the components, pull the tubes, and remove all the pots and other mechanical parts. Once we had pulled everything we could, the rest would go into the trash. All the parts would go into separate storage boxes by type and by value.
Why did we do this? Well, we told ourselves we were going to build some ham radio equipment. Of course, we never did and all the parts eventually got scrapped but when you're 10 years old and summer days lasted forever, it was fun way to spend a few hours.
Sometimes the journey is better the destination. When i was 10ish I’d build stage zero gentoo installations with dialup downloads. It’d take weeks and when i was done i didn’t really have anything to do with the computer.
So did I. In my case I wanted to build a ham receiver from a ARRL handbook design. Also bought some new parts with my hard earned money when I could get my dad to take me to Reno Radio in Detroit. The guys at Reno Radio were hams themselves and were always so darned encouraging to me.
But when I finally did get my license at age 14 my first station ended up being Heathkit gear I built myself.
I am loving the responses to your comment. I want to add that as a grown man in my forties I have a couple of Rasberry Pis and a BBC micros along with some interesting components from Aliexpress which I have done absolutely nothing with but pack neatly away for a few years now. One day.
I love that this is a blog post and not a video. I can read in my own time, not disturb others around me, and really peer at the pictures without having to pause at the exact correct moment.
Text and video are good at different things, telling the same story twice in different formats is rewarding to both you and your audience and there’s lots of overlap.
It also depends on __when__ you are consuming the material. I always need to do something while eating, and since my hands are often tied, a *video* format works better as I can just hit play without having to scroll or click on things. In other times though, I prefer text with images, especially if it's a static website without annoying JS.
Yeah that is true, too. I will say, on my end, if I am eating and watching a video it is generally just entertainment consumption like an actual TV show or a movie. I rarely spend that time to watch a video review of something.
But I definitely can understand a desire for both options.
I have a friend I help out who does this type of thing. We're currently working on some ART-13 Transmitters, which were used in WWII bombers and feature a then-secret technology called "autotune" which is a mechanical way to pre-set all the knobs to known positions at the flick of a switch. It's been quite an interesting journey.
BTW: Autotune does NOT actually tune the antenna network for maximum output, etc.
This is interesting. Perhaps you'll find it interesting that all the transceivers in Soviet (and allied) tanks during early cold War used this technology. I also saw it in big lorry mounted KF radios from the 50s~70s. There were a bunch of settings programmed in advance and then during use the operator would switch them then multiple dials would turn on their own internally setting each preset.
One of more popular devices still hunted and used by radio amateurs in countries in the region is the vacuum tube power amplifier for the big KF military radio R-140m. Unfortunately there is little info in English about it. It looked like this http://www.r140.de/
In modern times there is a control box made by some amateur that can be used to program auto tune presets in the R-140m linear amplifier. It actually tunes the antenna's network too.
I always am amazed by how chaotic point-to-point wiring is. Diodes hanging here, a capacitor there, with no real sense of organization. It's such a contrast from the ordered appearance of a PCB.
Yeah, those things were obviously designed to be hand-soldered, no automation possible. I guess this also makes them easy to repair ("easy" as in "not fiddly", obviously you still have to know what you're doing).
With a tube amp at least you have something with lasting value, these radios will unfortunately be turned into decoration items when analog radio is eventually switched off. Of course, as the article also mentions, they can still be used as amplifiers. How about installing a Bluetooth interface ;) ?
I had to trash a quad 22 setup, KT66 valves. It was submerged for a week in the recent Queensland floods but in truth, the wax potting and wiring was a mess this last decade or more. it was looking like my grandfathers axe to repair and 10x my budget. Still hurting about tossing it all.
I was like: how related is one really to the other, but you pulled me into that one. Now I have a different question: how much of an old artifact do you need to retain to still call it a "restoration", as opposed to a "replica"? (I realize this is not a question unique to this video.)
Very skillful, though! And the video style is very... soothing :)
The question you ask is called the Ship of Theseus problem and there has been no consensus on it despite arguing about it for 2300 years... Some metaphysical theories do entail an answer though, so maybe if you already subscribe to one of those already then you have your answer.
Great share. I bought this exact radio from a car boot sale for 5GBP back in the mid '90s and it's served me well ever since - until last year when my wife's cat knocked it off the shelf.
A refurb article on the exact same model is a sign from the thermionic gods that I have to get it on my workbench and fix it up.
Nice work, I like the connector for the speaker and keeping the large cap can stock looking. The original grill cloth look pretty nice, and the bright red connector for the speaker looks a bit out of place. Congrats on getting the project finished! It's a lovely result.
This particular radio appears to have an isolation transformer which makes it somewhat safer, but some older tube radios are actually connected directly to the mains line with no isolation transformer (this was done to save costs).
Those are especially dangerous to prod around in without the proper safety precautions when they are turned on, or even just plugged into the wall.
Just to be pedantic (I think it's ok given the venue...)
- All an isolation transformer (which is an external component you have to supply; it's never part of the radio) does is make the mains AC voltage inside the radio "float" in contrast with the voltage coming from the wall outlet (which is of course referenced to the actual ground outside your house). This makes things a little safer because if the chassis becomes live for any reason then there won't be a potential difference between the chassis and the ground that you're standing on, meaning you won't suddenly find yourself forming part of the circuit if you touch the chassis. In these old radios it's super easy for the chassis to become live so this is a good precaution.
- Isolation transformers do nothing for safety concerning the dangerously high DC voltages which the tubes run on. In the amp itself, the AC voltage comes in, hits a power transformer inside the amp (to get nice high voltages for the tubes), then is rectified into DC, then goes into the circuit to drive the tube plates and do all the other stuff it has to do. You can still get an almighty and quite easily fatal zap if your body provides a path between high DC voltage and the chassis (which is also the DC ground). Hence the rule, only work with one hand in a powered-on amp, because at least that way if you touch something then 350V of DC can't travel up one hand, through your heart, and back out the other arm.
- The final thing you might be referring to ("some older tube radios...") around cost savings is the archaic practice of skipping the power transformer entirely and connecting the wall AC voltage directly to the rectifier. This requires various compromises in the circuit (the DC voltage produced is quite low) and you _have_ to connect these with an isolation transformer or you're really asking for trouble - the chassis is all but guaranteed to be live. The original makers in the '40s and '50s, at least keen to be seen to try to avoid killing their customers, "solved" the problem by using plastic control knobs. Here's a good article: https://antiqueradio.org/safety.htm
>Isolation transformers do nothing for safety concerning the dangerously high DC voltages which the tubes run on.
Yes, you can still receive a fatal shock via one arm to the other even with an isolation transformer.
It's not true to say that it does nothing for safety, though. It provides isolation vs ground and prevents the circuit from being completed through your feet and the floor:
> It's not true to say that it does nothing for safety, though.
I didn't, I said it did nothing for safety concerning DC :) In the prior bullet I explained an iso transformer's contribution to safety regarding AC.
(Feet/floor not involved in the DC side. DC ground is the chassis, regardless of whether that's floating with respect to AC ground or not.)
EDIT: I'll double down on the pedantry 'cos this stuff does matter. There's no isolation transformer in this radio - it's a piece of benchtop equipment the author (wisely) chose to use. As I was getting at in my comment, I can't think of any radio or amplifier that incorporates an isolation transformer: at the time they were designed nobody cared, and nowadays the law requires you to include a separate chassis safety ground (for class 1 devices of course - class 2 being double insulated which is all but impossible on anything you could plug an external audio input into).
> It provides isolation vs ground and prevents the circuit from being completed through your feet and the floor:
Ah I think I see what you're getting at. Are you saying if your feet are at the same potential as the chassis then there's an alternative DC path to ground through your body, which the iso transformer breaks?
That's a good point, needed to think about that one a bit!
EDIT: Hmm, in that circumstance you'd be safe (from grounding DC through your feet) if the chassis was live! If the chassis was connected to AC neutral then your body could offer a path for high voltage DC to complete the circuit back to the chassis, but not if it was connected to AC line (hot). Quite an interesting thought.
Why did we do this? Well, we told ourselves we were going to build some ham radio equipment. Of course, we never did and all the parts eventually got scrapped but when you're 10 years old and summer days lasted forever, it was fun way to spend a few hours.