Vacuum Tube LEDs: Octal Tube Base Drilling

Clamping the octal tube into the Sherline let me set the XY=0 origin to the center of the base with the laser dot (visible near the front):

Octal tube clamped on Sherline mill

Octal tube clamped on Sherline mill

Find the edges, touch off the half the 32.2 mm diameter, then align the drill at XY=0 directly over the exposed evacuation tip:

Octal Tube - drill alignment

Octal Tube – drill alignment

Make a very shallow cut to verify the alignment:

Octal Tube - drill first touch

Octal Tube – drill first touch

Just inside the scuffed ring from the drill, you can see the fractured ring where the original one-piece Bakelite spigot / key / post broke off.

Then extract the drill from the chuck, file more relief behind the cutting edges so they actually cut, re-chuck, and continue the mission:

Octal Tube - drilling

Octal Tube – drilling

Pick a nice Bakelite ring out of the drill:

Octal Tube - drilled ring

Octal Tube – drilled ring

And eventually you can see all the way to the glass envelope:

Octal Tube - base opening

Octal Tube – base opening

The (knockoff) Neopixel LED sits directly below the evacuation tip and is about the same diameter, so much of that enlarged opening will be in shadow. Despite that, the tube does seem noticeably brighter:

Octal Tube - drilled base opening

Octal Tube – drilled base opening

Drilling that tube was so harrowing that I can’t imagine similar surgery on an intact octal base.

Perhaps just slicing off the tip of the Bakelite spigot and gluing a single very bright red/orange LED in place, rather using than a (knockoff) Neopixel a few millimeters away, will suffice.

Or just give up, top-light these tubes, and move on?

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Octal Tube Base Clamp

One of the octal tubes in my collection has a broken spigot / key post that lets some light in through the bottom of the normally opaque Bakelite base:

Octal socket in CD - LED diffraction

Octal socket in CD – LED diffraction

Perhaps drilling out the base would let more light pass around the evacuation tip, but that requires a shell drill to clear the tip. Some doodling suggested a drill with 12 mm OD and 8 mm ID, which was close enough to one of the smaller homebrew drills in my collection that I decided to see how it worked:

Shell drill assortment

Shell drill assortment

You (well, I) can’t freehand such a hole, particularly with a glass tip in the middle, so I needed a way to clamp the tube in either the drill press or the Sherline. A pad for the clamp screw in a V-block seemed appropriate:

Vacuum Tube Lights - Octal base clamp - Slic3r preview

Vacuum Tube Lights – Octal base clamp – Slic3r preview

The screw hole sits at the 1/3 point to put more pressure near the pin end of the base. Maybe that matters.

The setup looks like this, with a small red laser dot near the front of the base:

Octal tube clamped on Sherline mill

Octal tube clamped on Sherline mill

The tube rests on a random scrap of plastic, with the hope that the drill won’t apply enough pressure to break the glass envelope.

In normal use, the V-block would be oriented the other way to let you cross-drill the cylinder. In this end-on orientation, drilling torque can rotate the tube; compliant padding for more traction may be in order.

The OpenSCAD source code as a GitHub Gist now includes a module that spits out the clamp:

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Road Conditions: Rt 376 SB Near Maloney Rd

NYSDOT seems oddly reluctant to perform routine brush clearing along Rt 376 from Red Oaks Mill to the Hamlet of New Hackensack, despite the obvious hazard presented by the bushes:

Rt 376 SB shoulder overgrowth - 2016-09

Rt 376 SB shoulder overgrowth – 2016-09

I’ve reported this situation several times over the years, but, as you’ve seen in other situations, that has no effect.

If it were a pleasant back-country lane, rather than our main route to the Dutchess Rail Trail, perhaps having the greenery take over the shoulder wouldn’t matter quite so much:

Rt 376 SB - semitrailer

Rt 376 SB – semitrailer

Turns out the shoulder just north of Maloney has developed lethal cracks as the pavement subsides into the adjoining section of the Mighty Wappinger Creek. A bit more clearance would still be nice.

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Internet Of Things, Banking Division

We were sitting in the Credit Union and, as usual, I scouted out the WiFi situation:

IoT Thermostat in the Credit Union

IoT Thermostat in the Credit Union

Huh. Not what you’d expect to find in a bank lobby.

In case you haven’t seen what can happen with a thermostat, you can pwn a Nest.

Searching with the obvious keywords should provide plenty of reasons why the Internet of Things isn’t ready for prime time, not that that will slow it down in the least.

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Miniblind Bottom Rail Caps

A few days after installing the replacement cord caps, I bumped the bottom rail of the miniblind while opening the window and had one endcap disintegrate; apparently window hardware isn’t hardened against prolonged UV exposure. Who knew?

Fortunately, I can fix that:

Miniblind bottom rail caps

Miniblind bottom rail caps

Making the walls three threads wide provides enough room for a single solid infill thread:

Miniblind Endcaps - Slic3r Preview

Miniblind Endcaps – Slic3r Preview

The exterior shape comes from a hull wrapped around six circles: four to define the corner radius and a pair that bump the center out by the calculated chord height. The interior shape comes from a pair of chord-radius polygonal circles (they only have three facets across the length of the inside wall) that fit the bottom rail almost perfectly.

As always, natural PETG has a crystalline, slightly transparent, appearance:

Miniblind bottom rail cap installed

Miniblind bottom rail cap installed

I should spring for some opaque white filament, but that way lies madness; I might start caring what these things look like.

You can buy entire miniblinds for a few bucks a pop, but the last time we did that, they were different than the ones we had before. That wouldn’t matter if the standard miniblind mounting brackets fit our 1955 Anderson windows, but noooo they don’t: the custom adapters I machined for the first miniblind brackets, of course, didn’t fit the new miniblinds.

Now I can just snap the replacement endcaps (and cord pulls) in place, declare victory, and move on.

The OpenSCAD source code as a GitHub Gist:

The original doodle with some dimensions that didn’t withstand careful measurements:

Miniblind Endcap dimension doodle

Miniblind Endcap dimension doodle


Vacuum Tube LEDs: Miniature 7-pin Tubes With a Bottom Shield

Apart from the Bakelite bases on octal tubes, I figured there should be no problem shining a light up through the glass envelope. Come to find out that some of the tubes with Miniature 7 bases have an electrostatic shield (?) across the bottom that pretty well blocks the light.

This 6BJ6 has a neatly trimmed octagon:

6BJ6 - octagon shield

6BJ6 – octagon shield

The shield plate, if that’s what it is, doesn’t have a standardized shape. This 6CB6 sports a simple square:

6CB6 Square Shield

6CB6 Square Shield

The Box o’ Hollow State Electronics contains one 6BE6 tube (a heptode with five grids connected to four pins) without a shield:

6BE6 - Clear base

6BE6 – Clear base

Yeah, those pins are rather grotendous.

And another 6BE6 with a semitransparent smudge not connected to anything else; it would look accidental if it weren’t inside the tube:

6BE6 - Tinted Base

6BE6 – Tinted Base

All the shielded tubes are pentodes, for whatever difference that makes.

These tubes may be a bit too small compared to the hard drive platters; Novals will work just fine for my simple purposes.

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Raspberry Pi Serial vs. TNC-Pi2 vs. APRX

The APRX iGate program I’m using produces a hardware & software event log file:

2016-09-03 11:24:40.368 TTY /dev/serial0 read timeout. Closing TTY for later re-open.
2016-09-03 11:25:10.373 TTY /dev/serial0 Opened.
2016-09-03 11:32:05.485 CLOSE APRSIS heartbeat timeout
2016-09-03 11:32:15.495 CLOSE APRSIS reconnect
2016-09-03 11:32:15.776 CONNECT APRSIS
2016-09-03 12:25:11.154 TTY /dev/serial0 read timeout. Closing TTY for later re-open.
2016-09-03 12:25:46.154 TTY /dev/serial0 Opened.
2016-09-03 15:50:14.905 TTY /dev/serial0 read timeout. Closing TTY for later re-open.
2016-09-03 15:50:46.155 TTY /dev/serial0 Opened.
2016-09-03 16:50:51.155 TTY /dev/serial0 read timeout. Closing TTY for later re-open.
2016-09-03 16:51:26.155 TTY /dev/serial0 Opened.

I have no idea what’s going on with the “read timeout” messages. They seem to occur almost exactly a hour apart, except when they’re a few hours apart. The TNC-Pi2 board includes a PIC processor; maybe it loses track of something every now & again, but APRX only notices if it happens in the middle of a read operation.

The APRSIS server connection drops every few days and APRX seems well-equipped to tolerate that.

All in all, it’s working fine…