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Old 14th December 2020, 06:19 PM   #21
w5jag is offline w5jag  United States
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Possibly.

I think where the interlocks neck down to a narrow point would be weak points.

I think your idea of just making a support wall, which would just be two adjacent boxes with a bunch of corresponding pass through holes (?), is likely the best overall solution.
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Old 14th December 2020, 06:41 PM   #22
cogitech is offline cogitech  Canada
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Yes, two adjacent boxes with matching support walls with pass-through holes.

If this was the case, the dovetails interlocking the top surface would have almost zero load.

The side connections (where the two boxes meet at each side) could be interlocked with a "dovetail key". Difficult to explain, but I will see if I can draw it...

The dovetailing might look more interesting than a straight butt-joint (like the overlap) but this is a matter of personal taste.

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Old 14th December 2020, 07:01 PM   #23
w5jag is offline w5jag  United States
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You're also describing a "modular" SSE.

The SSE pcb, controls, switches, meters, etc., go in one box. The front box.

Power xfmr, OPT's, chokes, etc., go in one or more boxes. Call this the "power" box.

Put connectors on all the wiring, and to make a new amp, say change from KT88 to 6V6, just swap out the power box.

As long as a plastic chassis works. Still a big if.
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Old 14th December 2020, 07:05 PM   #24
cogitech is offline cogitech  Canada
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In my mind, the two boxes are epoxied together to form a single chassis, once the parts are pre-tested for a nice fit.

All wiring would then be permanent.

I am not saying the modular idea is bad. In fact, this could be designed with both options in mind.

Question: is it possible to fit SSE + OPTs on one module/box?

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Old 14th December 2020, 07:12 PM   #25
cogitech is offline cogitech  Canada
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By the way, I don't want to talk you into going in some other direction. I just love brainstorming about stuff like this.

Also, I have my concerns about this much heat near 3D printed parts. My concern is probably misguided by my lack of knowledge - I am just guessing that this plastic has quite a low melting point.

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Old 14th December 2020, 07:17 PM   #26
w5jag is offline w5jag  United States
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That's okay, all input welcomed.

My "projects" are always extremely fluid. I might have some goals in mind, but usually I just start soldering and see where that takes me.

I'm always okay with multiple directions.
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Old 14th December 2020, 08:15 PM   #27
w5jag is offline w5jag  United States
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Quote:
... The dovetailing might look more interesting than a straight butt-joint (like the overlap) but this is a matter of personal taste.
I'm thinking of using the OPT frames to hide the majority of the butt line.

Quote:
... Question: is it possible to fit SSE + OPTs on one module/box?
Depends on the size of the available printer. On my 500 x 500 at home base, space / volume is not an issue. On the 220 x 220 I have here at the lake, which is about the average size printer, it's the most important issue.

If you look at the other chassis I have on TinkerCad, the 215 x 215 one, you can see the big open hole to merge in the SSE PCB template. So you can see how much of the available space that pcb takes - quite a bit of it. In the left over space, you can see the hole patterns for some 10 watt open frame Edcors. The 15 watt open frame, and possibly the 25 watt open frame would also fit. I suspect the 10 and 15 watt GXSE transformers would also fit.

So, yes. Even on the small printers, you can get both on one box.

Quote:
... Also, I have my concerns about this much heat near 3D printed parts. My concern is probably misguided by my lack of knowledge - I am just guessing that this plastic has quite a low melting point.
PLA prints at about 190 C and above. So certainly it will turn fluid if it gets hot enough. Whether the PLA will work, or not, remains to be determined. My gut feeling is that it will work with reasonable planning, but I've had PLA objects deform just from being left in my car. It was summer, and Arkansas, but I didn't expect that.

There is such a thing as high heat PLA, that has better heat resistance qualities after it has been printed, and I have a kg of it that I got to use in another project, hopefully to avoid the car deformation problem ( haven't got to the point in that other project where it is ready to be installed in the car).

So all of this remains to be determined.
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Old 19th December 2020, 03:23 AM   #28
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I removed the power xfmr from the DHT SSE, so I could make a template for it.

The xfmr is a Merit P-2968, and is a pretty good chunk of iron: it's 3.75" H x 4.5" W x 3.8125" D; rated 400-0-400 at 110 ma, 5 at 3A, 2.5CT at 3.5 A, and 2.5CT at 15 amps. It was a stock catalog item for Merit, but I can't imagine what it's original application might have been that required a 15 amp secondary.

I've found it best to make templates for the various bits that can then be printed out and tested for correct fit and adjusted as necessary - this helps eliminate the possibility of making a long print using a lot of filament, and finding out it is not quite right when it is finished.

Anyway, the P-2968 template looks to be a good fit and ready to drop in a chassis. This thing is really heavy and runs hot, so should be a good test article.
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Old 9th January 2021, 08:43 PM   #29
w5jag is offline w5jag  United States
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So, here is power supply test article number one.

This was printed here at the lake, on the $100 USD box of parts printer, with ordinary PLA, 0.2mm layer height, 50% cubic infill, at 50 mm/second speed.

It's not a thing of beauty, but looks satisfactory for the immediate purpose as an experiment / test mule. It may look a bit better when the support remnants are cleaned out of the holes. Or it may not. But it's a start; you have to start somewhere. The article used about $4 USD worth of plastic and printed overnight into mid morning.

The deck and side walls are 5mm and physical strength appears to be completely satisfactory even with this very heavy transformer, at least with the transformer cold. At operating temperature may or may not be different, but I still have the earlier print out of the test transformer template that can be used as a strengthener or spacer if need be.

The overall height is 50 mm ( 45 mm usable ) and this looks to be marginal for vertical mounting an IEC connector, and for interior parts guts. I like things compact and low profile, but article two will likely be at least 60 mm overall height, maybe taller.

I put a rectifier tube socket hole in the top, which I will likely install to see how the ordinary PLA responds to the heat source, since rectifiers run with the heat of all the B+ going through them. I added a hole for some choke leads, but am not sure what choke I will be using, so I left mounting holes out.

I may skip a choke, and use something more modern like a MOSFET ripple filter. I am also leaning toward using the 5 vac taps on the power supply to power the 12AT7; this would eliminate one transformer, but require using something like 6AX5 as the rectifier, which was proven very satisfactory in the child resistant SSE. Or sand.

I probably won't do anything else on it over the weekend; I brought my RF travel kit ( a 16 inch tool box ) to the lake with me, and it is almost completely SMD / SMT parts, not a lot of through hole since they take up so much space, even in the smallest form factors. I am making up a high voltage / electron tube travel kit, but getting a decent variety of parts in it, considering the physical size of OPT's, power transformers, tube sockets, leaded parts, etc., is challenging. In any event, I left it back home.
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Old 10th January 2021, 05:10 AM   #30
cogitech is offline cogitech  Canada
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Very nice!

I did not get a printer yet, but I sure do still want one.

Keep up the nice work.
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