1940's 6L6 slat board transmitter and power supply

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1940's 6L6 slat board transmitter and power supply

Postby NT9K » Wed Nov 17, 2010 12:38 pm

Here is another project that I'm working on. This one still has a good bit of work that needs to be done, but coming along nicely. I tried to use as much vintage era parts as I could, down to the cloth covered wire. The coil is wound for 40m.

These transmitters were sometimes called sucker stick transmitters, because of the sticks used to hold the coil in place. There is a company that has a kit version out now, but I had started scrounging parts before the kit was produced and wanted to build mine from scratch.

The power supply in the first picture is nearly finished, all that's left is to wire it up. The transmitter still has a good bit of work that needs to be done.
Image
Image
73, Bill - NT9K
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Postby G0KZZ » Sat Nov 20, 2010 1:05 pm

Basket weave coils, oh yeah! 8)

Mark.
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Postby NT9K » Sat Nov 20, 2010 3:14 pm

Hi Mark, I'm setting the transmitter up on 40m and making slow progress. I'm just taking my time and trying to make it look nice. I've been collecting parts for over a year to build this thing. My goal is to have it working for the ARRL SKN on New Years Eve. I'd still like to fine a vintage 6L6 ST type tube. That one on there now is a new 6L6 from China. It just doesn't look right and is one of the only parts that isn't vintage. I'm sure I'll find one that I can afford someday. I can use the new one until then.
73, Bill - NT9K
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Postby G0KZZ » Mon Nov 22, 2010 12:48 am

Hiya Bill

I kept thinking that I'd heard (or seen) that design before.

I was just sitting here looking through a book on Morse keys (by KT4WJ) when I happened to spot the design info for the 6L6 TX.

I have a number of valves (tubes) laying around in my junk box, but I lack a suitable HT transformer. Years ago 240VAC in, to 240VAC + 6VAC out transformers were quite common, but these days they are like 'rocking horse droppings', hard to find and costly.

I have a pair of No38 WW2 AM transceivers lurking around (small, portable, short range phone tcvrs), that could possibly be made into something useful.

All of the solid state ham radio gear I repair and service at work seems so dull compared to the occasional valved (tubed) sets I get to work on. Valved sets always seems so 'alive', they are radios with a soul!

I spent many a happy hour building regenerative one valve sets in my youth, and for all of the modern gear I get to play with none of them compare to those 'one tube bloopers' for fun or satisfaction.

And they call it progress.....


73, Mark.
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Postby NT9K » Mon Nov 22, 2010 1:31 am

Mark, I first saw this circuit in Dave Ingram's column in November 2009 CQ magazine and did some research on the web and found that it originally appeared in 1946 CQ magazine. I found some pdf's on the web that helped me a lot. There is a company called pasttime projects that sells almost the same thing in a kit form, but it isn't very cheap. It isn't exactly the same either. They are using a voltage double in the power supply and they skimped on some of the parts in the transmitter, like the RFC and bypass caps.

Yes, finding the transformer was one of the hardest parts for me too. I finally found one, but it was rusty. I spent a week restoring it and got it looking pretty nice. The one I found is 385-0-385 at 90mA, 6.3v at 2A, 5v at 2A. My regulator tube is a 5Y3G and needs the 5v secondary.

Once I get it working, I'd like to build a matching one tube regen, but I still haven't found just the right circuit I want to try just yet. It's been fun building it, so far. I'll post more pictures as I get closer to finishing it.
73, Bill - NT9K
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Postby NT9K » Sat Dec 11, 2010 5:45 pm

It's finished now. My new big bottle 6L6G ST type tube just came in the mail today. I took another picture of it with the new tube and put it on the new webpage I'm working on here:
http://www.nt9k.com/slatboard.html

I'll add more stuff to the page, like links to parts sources in case anyone else wants to try building one too. The new tube is a lot bigger and looks a lot better. I wanted one with clear glass, so I could see it glow!
73, Bill NT9K
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Postby G0KZZ » Thu Dec 16, 2010 9:19 pm

Hi Bill

I've seen a few metal bodied 6L6's on the web e.g. ebay item number 130464982916 and so on.

Can you use the metal bodied valves (sorry tubes) in your circuit?

I have a number of WWII tubes here (made by Mazda if I recall), and they all tend to be metal bodied, but I guess that was just to increase the level of blast protection!

Talking about HT transformers, many years ago (when I was young and foolish, now I'm just plain foolish!), I had the bright idea of winding my own transformer.

Using a calculation I found in an old book I carefully worked out the winding ratio, and made up a small transformer.

I wish someone had told me about inductance at the time. I plugged it in and flicked the mains switch. There was a TREMENDOUS bang along with a BRILLIANT flash of light, and I think I may have pooped myself hi hi.

After I got over the shock I found to my horror that I had blown the mains fuse downstairs, and the contacts in the switch were welded closed.

It was at that moment that I gave up on the idea of becoming a world famous transformer maker, and went back to buying them :D

73, Mark.
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Postby NT9K » Fri Dec 17, 2010 1:43 am

Hi Mark, yes you can use the metal 6L6 tubes. I just prefer glass types and clear glass, so I can see them glow. I have another tube should be here tomorrow. It's a clear glass 6V6G coke bottle shaped tube and will also work in my slat board, but will produce a bit less wattage. I'm not sure if it will get me down to QRP levels or not, but that was also a consideration. Another reason to use a 6V6 instead of the 6L6 is it draws less amperage and is easier on the crystals. It's quite possible that the 6L6G tube will fracture the crystal. I hope not, those FT-243 crystals are hard to come by. So, just in case, I plan to use a less than favorite crystal when I tune it up the first time.

What I am waiting for is to finish building my MagicBox T/R switch kit. That will let me safely use my Kenwood as the receiver without damaging the front end. Eventually, I want to build a slat board regen receiver. That's a ways off though.
73, Bill - NT9K
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Postby G0KZZ » Fri Dec 17, 2010 6:47 pm

Hiya Bill

OK on glass-vs-metal tubes.

You mention about the tube destroying the crystals. A 'dodge' I read about in an old radio book was to fit a small torch (flashlight) bulb in series with the xtal. Not only can you watch the glow (telling you that the circuit is oscillating), if the oscillation becomes too excessive the torch bulb will blow similar to a fuse, thus protecting the xtal.

I love regenerative receivers. I used to build loads of the things years ago (when I could still obtain the various HT parts from old TV sets). MFJ produce a regenerative receiver kit (I don't own one, but had 'hands on' experience of one owned by one of our customers), and they work quite well.

I have a Ten-Tec T1253 regenerative receiver kit to build here. It was my Christmas present from my xyl last year! Just not got around to building it yet :D I've seen them in action on Youtube and they are fine performers.

There's also a Science Fair "Globe Patrol" receiver on it's way to me (snow + xmas = slow post), which I can't wait to have a listen on. I remember them in the old Tandy (Radio Shack) catalogues here in the UK when I was in my teens. They were sold as kits as far as I can remember. Only three transistors! When I was younger my 'ideal' shortwave receiver was a Globe Patrol.

Image

I have a design here that was originally intended as a space filler in an electronics magazine in the UK. It uses two transistors and is very easy to build. The original design was for a MW AM receiver, but I soon found that the design worked well into the HF bands, and also down on LF and VLF too!

I can feel my soldering iron hand 'twitching' with all this talk about homebrew receivers :wink:

Best 73, Mark.
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Postby NT9K » Sat Dec 18, 2010 12:01 pm

Hi Mark, is that picture the one that you have on the way? It sure is clean! I posted a few more pictures on my slatboard webpage of the pictures of the slatboard receiver from the Nov 2009 CQ article. It uses a single 12AT7 valve and is built on the wooden slatboard chassis. I may not build the exact same regen, but I do want it on a wooden frame to match the transmitter and power supply.

I haven't put the #47 torch in the circuit yet, I built it exactly like the circuit shown on the webpage. I took a picture of it and it's towards the bottom of the page. Here:
http://www.nt9k.com/slatboard.html
73, Bill - NT9K
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Postby G0KZZ » Sat Dec 18, 2010 10:35 pm

Hiya Bill

No, the photo was just one that I came across on the web that I used to illustrate the post.

The one that's on the way to me is in similar condition though (I have to pay another $40-$50 in taxes and handling fees over here :cry: )

I have a full copy of the manual (in electronic format) so any tweeking can be done where needed. I'm really looking forward to trying it out, and as mentioned above I've been 'looking' at them for about thirty years or more so it's about time I got my hands on one!

It would make a nice Youtube video when you build your regenerative RX, you could show it in action!

I have about 200 tubes of various types in my junk box, but another part that's getting harder to come by are the bases for them, especially the octal ones.

I did buy a few via ebay a while ago, but they were not as described, so I wasted my money on them I guess...

I have a pair of WWII No38 (I think) ex mil AM HF transceivers, complete with throat mics and headsets, which could be stripped down for valves, bases, HT caps etc, but I'm a bit reluctant to break them down since they are also getting rarer these days.

The outsides look like they've been 'through the wars', but internally they're mint.

I'm still stuck for somewhere to work on projects here, trying to build things out of a shoe box shack is no fun. I have plenty of ideas but no workspace :( I have to content myself with oiling my Morse Keys and dusting my radio :?

To be honest, it's only by seeing projects such as yours that keeps my interest in the hobby these days. It's nice to see that there are still some 'real' Radio Amateurs left.

Keep up the building Bill. My hobby is kept alive by your handywork, and I suspect that I'm not the only one :wink:

Best 73, Mark.
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Postby NT9K » Sun Dec 19, 2010 1:39 am

Real nice comments Mark! Sometimes, I think that I like building gear more than I do operating it. I have so many projects in the works, it isn't funny. One way I keep them organized is to store them in plastic food containers with lids. Especially the kits with small parts. Having lids that seal keeps me from loosing parts. Most of the time, I build my stuff in the living room floor. I just spread out an old towel to work on and wrap it up when I'm tired of it.

Again, thanks for the FB comments. I've been sick all day and you made my day! 73..
73, Bill - NT9K
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