Lenovo Headset Boom: Repair Faceplant

I picked up a Lenovo headset on sale and over the course of a few weeks the mic boom pivot worked itself loose, until I finally dismantled the left ear cup to see what was inside. Come to find out that the mic boom has a molded threaded section held into the cup with a simple nut and no locking mechanism at all:

Lenovo headset - OEM mic boom pivot nut
Lenovo headset – OEM mic boom pivot nut

I think the metal washer was intended as a low-friction pivot atop the compliant silicone (?) washer underneath, but the net effect was that the nut unscrewed a little bit more every time the mic boom moved. By the time I got in there, the nut was completely off the threads.

The original nut left a thread or two showing, so I found a thicker replacement nut with a better grip. The obvious solution involves a dab of Loctite to jam the nut in position, but we all know that some plastics, most notably acrylic, react badly to threadlocker and tend to disintegrate. Although I considered just epoxying the nut in place, that seems so, well, permanent.

So I dutifully tested a dab of Loctite on an inconspicuous spot inside the ear cup, got no reaction at all, put a drop on the boom pivot threads, and reassembled everything:

Lenovo headset - replacement mic boom pivot nut
Lenovo headset – replacement mic boom pivot nut

Alas, by the time I got back upstairs and hung the mic on the rack, the boom fell completely out of the earcup! Back in the Basement Laboratory, I dismantled the thing again and confronted this mess:

Lenovo headset- Acrylic plastic vs. threadlock
Lenovo headset- Acrylic plastic vs. threadlock

Huh. The ear cup isn’t made of the same plastic as the mic boom: one shrugs off threadlock, the other disintegrates.

That’s obvious in retrospect, eh?

The only threads that aren’t ruined lie completely within the ear cup frame, with just a stub sticking up around the wire. So I cleaned things up and did what I should have done originally: put a dab of epoxy inside the nut to bind the pivot firmly in place. A snippet of unshrunk heatshrink tubing around the wire provides a bit of strain relief:

Lenovo headset - boom pivot nut with epoxy
Lenovo headset – boom pivot nut with epoxy

There’s no longer any space for the compliant washer in that stack, so we’ll see how long this lasts. The next repair will certainly venture far inside non-economical territory. I like the headphones, though.

Memo to Self: Check in an inconspicuous spot on the same material.

Sony NP-FS11 Battery Rebuild Repair

One of the battery packs I’d re-rebuilt failed in short order, which I wrote off to a bad cell and tossed it on the heap. Having recently found a small stack of Round Tuits, I’ve been cleaning off the bench and took the pack apart again. Turns out I blundered the solder joint between the positive cell terminal and the protective circuit board: the strap in the foreground joining those two points didn’t make a good connection to the cells.

I suppose it was just another cold solder joint:

Rebuilt NP-FS11 battery - Pack A
Rebuilt NP-FS11 battery – Pack A

That’s an awkward joint at best, because the protective circuit doesn’t come willingly out of the housing and you (well, I) must solder it without scorching the cells, the plastic case, or the PCB. It can be done, but it’s not easy.

Charged it up and it’s back in the A/B/C pack rotation again.

Memo to Self: Tough to find good repairmen these days, eh?

Macro Lens Focus Stacking

Begin by mounting the Canon SX230HS on the macro lens adapter, zooming to about the maximum, fiddling with a ruler to put the end at the closest focus point, and eventually get an overall view like this:

Ruler - macro mid-focus
Ruler – macro mid-focus

The images below were batch cropped from similar views with ImageMagick:

for f in $(seq 17 22) ; do convert -crop '1500x1126+1900+1800' \
   img_18${f}.jpg img_18${f}-crop.jpg ; done

Yes, I’ve taken a bit over 1800 images since getting that camera… the old DSC-F505V recently rolled over at 10K images.

Take a set of six identically exposed pictures starting with the focus at infinity (about 95 mm in real life):

macro far focus
macro far focus

And ending with the closest focus at about 1 meter for this zoom setting (and 80 mm in real life):

macro near focus
macro near focus

Then apply enfuse (from the Ubuntu repositories) with a handful of parameters suggested there that combine the sharpest parts of each image into a single image:

enfuse --verbose --exposure-weight=0 --saturation-weight=0 \
   --contrast-weight=1 --hard-mask --output=stacked.jpg \

Which produces this nice result:

Ruler - macro combined focus
Ruler – macro combined focus

It’s not perfect, it needs a few more intermediate images, there’s fringing around high-contrast edges, and so forth and so on, but for a first pass it ain’t bad at all.

I bar-clamped the camera & macro adapter to the desk in order to eliminate all motion. My usual tripod mount for the macro setup isn’t all that stable and the microscope stand isn’t particularly rigid, either, so I must improve a bunch of mechanical structures. In principle, you can post-process the pictures to realign them, although the tolerances seem daunting enough to make mechanical fixturing look downright attractive by comparison.

Now, if it should turn out that the SX230HS supports the CHDK USB remote trigger, that’d be nice. Or maybe the right way to proceed involves converting the problem to A Simple Matter of Software by writing a CHDK script that tweaks the focus by multiples rather than increments.

Canon Hack Development Kit for SX230HS

Although the macro lens adapter and microscope mount work well enough, the relatively small sensor and lens in my Canon SX230HS make for a razor-thin depth of field:

Macro lens depth of field
Macro lens depth of field

Those are, of course, millimeter divisions on the ruler.

A bit of rummaging leads to the notion of Focus Stacking, which involves taking a sequence of images with identical exposure settings and different focus points, then compositing the in-focus parts of each image to produce a single image with everything in focus. Although some examples show a manual process involving layers in, say, The GIMP or Photoshop, I think an automated process would be better.

Given that I have a Canon SX230HS camera, the first step is to download the proper version of the Canon Hack Development Kit, unpack it onto a spare SD card, and get used to it.

As it turns out, the focus bracketing works exactly as intended, but doesn’t do quite what I need: it changes the focus in linear steps by adding a constant bracketing distance. The macro lens adapter drags the “infinity” focus point inward to maybe 15 mm beyond the innermost focus point, but the camera’s focus range still shows 1 m to ∞. Stepping in 1 m increments generates a bazillion pictures that don’t differ by much at all after 5 m, but you still need a few near the far end.

However, it seems the only way to get a bazillion pictures is by holding the shutter button down with the drive mode set to Continuous, as the camera’s Custom Timer mode has a 10 shot upper limit. If I must do that, I may as well adjust the focus manually: the assumption being that the camera shall be firmly mounted to keep the pix in alignment, which currently isn’t true in any of my setups and certainly won’t be true with my finger on the button.

The camera already has exposure bracketing, although not to the extreme range available through CHDK. RAW images (or the roughly equivalent DNG format) might come in handy at some point, but right now they’re just a temping digression available only through CHDK.

If I’m going to keep using CHDK, I must conjure up an artificial NB-5L battery with an external power source. Those cheap eBay batteries work fine for the usual duty cycle, but constant zooming & focusing & suchlike chew them pretty hard…

Gas Flareoff

While I was on that ride, I found this at the bottom of a smoky pillar rising along the Hudson River:

Turns out Central Hudson Gas & Electric has a pipeline under the Hudson at that point and I’d admired their spherical storage tank from ground level some years back:

Gas Storage Tank
Gas Storage Tank

I don’t know what they’re flaring off, but it looks messier than, say, propane. There’s another flare nozzle just out of the picture on the lower left, both along the edge of the circular concrete pad left over from a cylindrical storage tank, so they do this often enough to have some permanent infrastructure.