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Old 21st November 2020, 10:56 PM   #11
w5jag is offline w5jag  United States
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All that said, Iím not going to use 6B4G in the directly heated SSE Iím going to build in this thread. The 2A3 SSE is been there, done that, and on top of that, I havenít been able to scrounge any 6B4G tubes locally.

So Iím going to use a more obscure directly heated octal - the type 1619. The type 1619 is an RF beam power tetrode, on a type 7AC base, EXCEPT that it has no cathode - the beam forming plates are brought out directly to pin 8. The filamentary cathode is the usual 2.5 volts, and I already have some 1619 tubes, so I donít have to buy anything new, except for maybe some better OPTís. Type 1619 will use a 7 to 8K OPT, and since it has extra grids, playing with pentode and distributed load / ultra linear will be possible.

Some people say that the 1619 is a poor mans 45. I find that hard to believe since one is a triode, and the other is an RF beam tetrode, but whatever. I guess we will find out what 1619 can do in due course.

Right now my point of indecision is the 3D printing aspect. I have a 500 x 500 mm printer, so I can print pretty much a full size anything, but the usual printer is in the 220mm x 220mm, maybe a bit bigger, size. So I'm thinking about doing it in pieces to start with, so there will be SSE models available for ordinary size printers.

That would mean putting the power transformer on a separate chassis, and maybe the choke. Ordinarily, that would be of no consequence, but since each power tube has its own filament winding, that will mean some pretty long leads in the cathode bias circuitry for the amp. I'm not sure if that will cause any adverse effect or not.
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Old 27th November 2020, 08:10 PM   #12
w5jag is offline w5jag  United States
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See 11/27/2020 edit to post #1.
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Old 3rd December 2020, 04:56 PM   #13
cogitech is offline cogitech  Canada
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This is all very cool! More than anything, it has got me thinking about getting a 3D printer. My wife and kids keep bugging me to make a Christmas wish list.

The thing is, where do I even begin to figure out what I want to get? I started looking on Amazon and found the Creality Ender-3 Pro. I like the fact that it is open source and built with off-the-shelf parts. I plan to use Linux, running (I think) Ultimaker Cura software.

Is there a good source of info for all things 3D printer?

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Old 3rd December 2020, 06:34 PM   #14
w5jag is offline w5jag  United States
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I think 3D printers are about the neatest thing since sliced bread, but as a non technical person, I have found them to be a substantial learning curve. I am very far from knowledgeable about them.

First, there is the printer itself.

Then, you have to get a model from somewhere, or if one does not exist, you have to make your own or modify an existing model. This means learning elementary CAD work. Making my SSE "models" downloadable from TinkerCad is like handing someone source code - they can freely modify ( aka fix my mistakes ) the models.

Finally, there is the slicer program that takes the 3D model and "slices" it into a bunch of 2D parts printed one on top of another, and spits it out in a machine code the printer can use to run the steppers. These programs may be the most complicated part of the whole deal.

If there is an all in one site for all things 3D, something along the lines of 3D Printing for Dummies, I would be interested in knowing about it as well.

I think any of the Creality printers would be a good choice; they come as a knockdown kit and assemble in an hour or so, and look to be reasonably good quality. Just make sure it has a heated print bed. I think all of the Creality do, but some box of parts printers may not. I have a CR10S-5 (500 x 500 x 500 mm ) at the office. I can say that the Tronxy P802 "box of parts" 3D printer at our second house has taught me quite a bit abut these things, and has helped move me along the learning curve.

I have turned out some really, really, crappy looking stuff so far. I expect to turn out more crappy looking stuff over the course of this project before it's done, but all of these interlocking parts - printer, CAD, and slicer - are finally beginning to converge for me, so I'm looking forward to see if 3D printing is going to be useful for this type of DIY electronics.
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Old 3rd December 2020, 08:37 PM   #15
cogitech is offline cogitech  Canada
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Cheers Win! Good luck with this project and with 3D printing in general! I think it is something I could really nerd out with and enjoy.
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Old 13th December 2020, 08:56 PM   #16
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The little printer here at the lake is only 220 x 220 mm which puts a practical limit of about 215 x 215 mm, more realistically closer to 210 x 210 mm, on anything created by it in a single piece. The Merit P-2968 power xfmr and SSE PCB cannot both fit in this space, not to mention the other iron needed, necessitating a two box solution if I use this xfmr.

A two box solution requires 16 interconnections with the main chassis, 7 of which have high voltage. If I move the rectifier and most of the B+ parts to the power supply box, I can reduce this to 10 interconnections, only one of which is high voltage. I'm not real familiar with current connector options that can also handle high voltage. AFAIK, the standard is to have the female connector on the power supply end, to reduce the risk of accidental electrocution if the cable gets disconnected while the power supply is live.

It looks like the classic Cinch-Jones connectors are still available in a 16 pin configuration, but the 16 pin shrouded female cable connector is expensive. The 16 pin male chassis connector is cheap. I think I might be able to make a cable shroud with the printer, and use a 16 pin female chassis connector on the power supply cable, that would still be safe. That would cut the cost of the Cinch-Jones parts by about two thirds. I think 18 pin parts are also available, which could leave two pins as a safety to kill the power supply if it became disconnected from the amp.

10 interconnects are easy to manage. The old school 11 pin Amphenol style cable and chassis connectors used in tens of thousands of ham radio sets are still readily available, at about the same cost as the Cinch-Jones parts, i.e not cheap if you're a tight fisted hobbyist ( I am ).

Finally, I guess octal chassis sockets and octal tube bases would also work. That is probably the least expensive and least desirable alternative, since it would require two cable sets. I might go this route, since I already have suitable chassis mount octal sockets on hand. The holes will be printed anyway, so it's not like it is any extra effort to double the number of holes that have to be made. Two cables obviously makes it easier to hook the cables up wrong. w5jag's law says that will eventually happen without some type of safeguard.

Interestingly, I was looking at / pricing out available xfmrs yesterday, and I think I could get everything on one 215 x 215 mm chassis if I am willing to disregard some of the traditional chassis layout norms. That would also require buying a bunch of transformers I don't presently have, which I am trying to avoid - I'm trying to keep the new iron acquisition limited to just some new 8K ish OPT's.

If I go with a single box solution, it will be 12 x 10 inch, the same size as the existing child resistant SSE ( still running strong coming up on seven ( 7 ) Years now ), and the existing DHT SSE breadboard in post #1. It is very easy to get everything in a chassis that size, with quite a bit of room to spare.

I almost ordered some new Edcor OPT's yesterday, but the shipping charges just really rub me the wrong way. It looks to cost as much as a single transformer to ship a pair of OPT's to me - and I'm only two states away from the factory. I may try to get a price on some Transcendars since he is winding again. I have some 7K OPT's right now, they're just not very good. And I have some Hammond 125ESE OPT's I'm not using at the moment. Actually, I have a lot of OPT's I'm not using right now- I just don't have the ones I want / need for this project.
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Old 13th December 2020, 09:03 PM   #17
cogitech is offline cogitech  Canada
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Is it possible to build one chassis out of inter-locking/inter-connected pieces?
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Old 13th December 2020, 09:15 PM   #18
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I'm sure it could be done, but I don't know what kind of structural rigidity one might get from it. And given the weight of even modest iron parts, I think high rigidity is a requirement. ( edit: ) I'm also trying to avoid visible fastners as much as possible - take that away, and more options are available.

A possibility / work around might be to use some of the parts that would ordinarily be fastened down, like the OPT's, as structural components of the "design" to join pieces together and add some rigidity to the complete structure.

Because I have another 500 x 500 mm printer, I've not given much thought to making big parts on a small printer, since I have a big printer for that.

But it's an interesting concept, and worth some thought being put to it - I'm obviously still in the all talk, no action stage at this point.
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Old 14th December 2020, 12:19 AM   #19
w5jag is offline w5jag  United States
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Okay, FWIW, I made a quickie "overlapping" chassis, and made it public in TinkerCad, so anyone can look at it and play / change / fix / break / modify it. Same #tags as the other pieces.

It would print out to about 200 mm x 360 mm ( 8 ish x 14 ish inches ), so, not huge, but plenty usable and a lot bigger than you would otherwise get off one of the little printers.

It (should have) has a 20mm overlap on the top plate, and I put 4 dowel post holes in the side walls that can have dowels pressed in for friction fit, or glued for strength, and some printable dowels to fit, to stabilize the sides.

It may or may not work - someone would have to print out enough of it to find out, and check the fit. It might ( or might not ) be best to flip the underlap piece 90 degrees on end and print it vertically, to avoid having to print support under the underlap. In that instance, the dowel holes on that piece could be made solid, and printed as posts to interlock to the other piece. It will probably probably require a tiny bit of light sanding on the overlap or underlap and dowels / posts to get a "perfect" fit.

More sanding if the underlap is printed with support under it. Unfortunately, gravity refuses to allow printing stuff that is hanging out in free space.

It may be that the underlap / overlap is a poor / dead end idea, and better ease of print and maybe better rigidity could be obtained with post holes and dowels similar to the side walls. Might not look as good, though.

Some experimenting will be required.

3D design interlocking chassis | Tinkercad
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Old 14th December 2020, 05:17 PM   #20
cogitech is offline cogitech  Canada
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That's pretty cool, Win, and a good start.

Maybe a dovetail would be easier to print. It would also need some support posts... or even a support wall with lots of pass-through holes for cabling/connections.

Click the image to open in full size.

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