The Newton 300B

[Thermionic Idler]

I thought I'd start a new thread for the build. Here's where I'm at so far.

To recap, here's the schematic. It's a version of Lynn Olson's "Symmetric Reichert" which I don't think has actually been built. The coupling cap values have been increased and the driver valve stage swapped out for 6V6's in triode mode.



Here is an initial artists impression of how it's expected to look when built (note there will be some ventilation slots but I'm anticipating no visible screws other than those around the edge. Ant is going to do the wood surrounds and transformer covers for me, although I've yet to clear the latest design version with him!



Here's the same with the wood casing stripped away showing the position of the transformers on top, and some of what's underneath



And here's a more detailed view of the inside. The main issue was figuring out how to fit everything around all those motor run capacitors. Each monoblock is about 2' wide by 1' deep and pretty much all the interior space is used.



Yes I know I have octal sockets in the 300B locations. The Teflon UX4 sockets I'm using however, have the same dimensions as a standard octal so it was easier for modelling purposes to use the octal socket I'd drawn out before.

I have all the transformers and chokes except for one back-ordered mains transformer, due to arrive in a few days. The HiFiCollective order is here too. Sent orders in to RS and Mouser today.

Next step, I need to drill out all the holes and figure out what spacers, screws and nuts I need.

[Thermionic Idler]

A PDF of the schematic (which is slightly better resolution than the JPEG I posted above) can be viewed by following this link.

[Thermionic Idler]

Now that's a proper capacitor.

[pre65]

Big enough, how are you going to mount it ?

[Ant]

Its a bolt in one, ive got some of those somewhere

[Greg]

Big enough, how are you going to mount it ?

Are you talking about the capacitor?

[pre65]

Big enough, how are you going to mount it ?

Are you talking about the capacitor?

Do I detect a touch of innuendo there Greg ?

[Thermionic Idler]

Big enough, how are you going to mount it ?

See third picture, post 1. There’s a threaded stud on each one, that goes through the rear panel and they’ll sit horizontally.. Half the interior space is taken up with these. The hours of Tetris/cad work that’s gone into these has been figuring out how to fit everything around them and still have a build that fits on top of a bookshelf.

[pre65]

You might be OK if they are not electrolytic capacitors, but I got caught out once by not realising the stud was coupled to the negative terminal.

Are you OK for the stud mounting nuts ? If not measure the size and let me know. Could possibly be M10 or M12.

[Thermionic Idler]

You might be OK if they are not electrolytic capacitors, but I got caught out once by not realising the stud was coupled to the negative terminal.

Are you OK for the stud mounting nuts ? If not measure the size and let me know. Could possibly be M10 or M12.

Interesting! I don't think that's a problem here, nothing in the datasheet suggests the can is connected.

I'm also good for the mounting nuts thanks, Mouser supplied the correct ones along with anti-shake washers. They are M8 for the 20 and 40 uf values, and M12 for the 80 uf. The chassis will have a circular section ground out on the rear side around each hole, to ensure the can is properly grounded when attached.

[Thermionic Idler]

Modelling is now completed, down to literally evey nut and bolt. The inside is expected to look something like this, but with a few more wires and resistors obviously.

[Thermionic Idler]

The panels have been manufactured and shipped from Schaeffer, they are due here next Monday. Assuming no manufacturing defects (I did have issues last time around with the "bend notch") they will have the 90 degree bend applied and then over to Ant to do the wood frames and tx covers.

There's always a moment of anxiety around the panels arriving. This time around, because I was using an updated version of TurboCAD, I was able to export a DXF file which included all the 2D cutouts without FrontPanel rejecting it. That reduced the amount of manual data entry I had to do in the FrontPanel software, I mostly only had to worry about the 3D elements (blind holes, standoffs etc). I then exported a DXF from Frontpanel and re-imported it to TurboCAD, overlaying my original panel design, to sanity-check that nothing had been missed or was out of place (I did find, and correct, one error).

Even with all that checking, it still doesn't stop the worry! I occasionally have a moment of panic and have to open a file to check I haven't missed something.

The wiring layout has also been (roughly) planned, along with the build order. As always, this has consumed a lot more of my time than expected, but the design is one of those that has largely "fallen into place". I'm hoping this portends good things.

[Thermionic Idler]

Panels arrived from Schaeffer, all looking good:



And the reverse side, showing the various studs and standoffs.



The other panel is identical, except for the mirror-imaging.

[Michael L]

The panels have been manufactured and shipped from Schaeffer,

Is this a USA based company? Was it very expensive to get the panels made and shipped here?
Are there any firms in the UK or Europe who do the same work?

Thanks

[IslandPink]

Phwoarr !