Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Quite some time ago, I picked up a nice monitor that turned out to be a debranded (all OEM labels removed or covered) HP w2408. It eventually became erratic, refusing to turn on or return from power-save mode, so I took it apart. All the caps looked good and seemed to have low ESR, except for the big one in the middle of the power supply board:
HP 2408 monitor power supply – HV cap
It’s 30 mm in diameter, with 10 mm lead spacing, and stands a squat 26 mm tall, ignoring a millimeter or two of bulge in its should-be-flat black cap:
HP 2408 monitor power supply – HV cap bulge
Having never seen one of that size before, I sent a note and picture to folks who sell re-capping kits for monitors, in the hope that they’ll have a lead.
Lunar eclipses happens so rarely it’s worth going outdoors into the dark:
Supermoon eclipse 2015-09-27 2250 – ISO 125 2 s
That’s at the camera’s automatic ISO 125 setting. Forcing the camera to ISO 1000 boosts the grain and brings out the stars to show just how fast the universe rotates around the earth…
One second:
Supermoon eclipse 2015-09-27 2308 – ISO 1000 1 s
Two seconds:
Supermoon eclipse 2015-09-27 2308 – ISO 1000 2 s
Four seconds:
Supermoon eclipse 2015-09-27 2308 – ISO 1000 4 s
Taken with the Sony DSC-H5 and the 1.7 teleadapter atop an ordinary camera tripod, full manual mode, wide open aperture at f/3.5, infinity focus, zoomed to the optical limit, 2 second shutter delay. Worked surprisingly well, all things considered.
Mad props to the folks who worked out orbital mechanics from first principles, based on observations with state-of-the-art hardware consisting of dials and pointers and small glass, in a time when religion claimed the answers and brooked no competition.
ISS Moon Transit – 2015-08-02 – NASA 19599509214_68eb2ae39f_o
The next eclipse tetrad starting in 2032 won’t be visible from North America and, alas, we surely won’t be around for the ones after that. Astronomy introduces you to deep time and deep space.
I duct-taped a pair of D cells onto the case and returned it to the bedroom shelf. According to the date scrawled on the tape, that was five years ago: 26 November 2010.
Over the last few months, the LED gradually faded from a blink to a steady glow as the battery voltage dropped below 2 V and the WWVB receiver output no longer reached the MOSFET’s threshold.
We’ll see how long these last:
Alpha Geek Clock – new batteries
Yeah, I should probably do something involving 3D printing…
The big bag o’ new-old-stock Inmac ball-point plotter pens had five different colors, so I popped a black ceramic tip pen in Slot 0 and ran off Yet Another Superformula Demo Plot:
HP 7475A – Inmac ball pens – weak blue
All the ball pens produce spidery lines, but the blue pen seemed intermittent. Another blue pen from the bag behaved the same way, so I pulled the tip outward and tucked a wrap of fine copper wire underneath. You can see the wire peeking out at about 5 o’clock, with the end at 3-ish:
HP 7475A – Inmac ball pen – wire spacer
The wire holds the tip slightly further away from the locating flange and, presumably, makes it press slightly harder against the paper:
HP 7475A – Inmac ball pen – stock vs. extended
A bit more pressure helped, but not enough to make it dependable, particularly during startup on the legend characters:
HP 7475A – Inmac ball pens – extended blue
That black line comes from an ordinary fiber-tip pen that looks like a crayon on a paper towel by comparison with the hair-fine ball point lines.
Delicacy doesn’t count for much in these plots, so I’ll save the ball pens for special occasions. If, that is, I can think of any…
Being that type of guy, I measure the single-layer skirt threads to keep track of the platform alignment. Most of the time, nothing happens, because the M2 has a remarkably stable platform, but some of the objects I’d done in early August showed more than the usual variation and, worryingly, no discernible trend.
Adjusting the platform alignment between each of those sets produced no consistent effect, which is most unusual. The X in the bottom set shows where that thinwall box came unstuck from the platform, indicating that the clearance was considerably more than the nominal 0.25 mm layer height.
Peering under platform revealed something else that was quite unusual:
M3 washer – bad seating
That washer should be flat against the spider mounting plate. My first thought was a burr on the plate, but that didn’t make any sense, as the plate was clean & smooth when I installed the platform; I’d enlarged those holes with a fine file and would have checked for burrs as part of that operation.
Removing the screw nut and extracting the washer revealed the true problem:
M3 washer with burrs
It’s a bad washer!
Tossing that one in the trash and installing a good washer put everything in order:
M3 washer – proper seating
Well, that’s after re-doing the alignment to un-do the previous flailing around, of course.
As nearly as I can tell, that washer sat there without causing any trouble since I installed the hotrod platform. or, more likely, when I repaired a failed screw. In late July I poked the platform to measure how much it moved under pressure, which apparently dislodged the washer and put the burr in play.
That’s how sensitive a 3D printer is to mechanical problems…
The Smell of Molten Projects in the Morning 