The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Tag: Repairs

If it used to work, it can work again

  • Bafang Headlight Circuit Current Limit

    Bafang Headlight Circuit Current Limit

    Having just replaced Rev 1 of the amber running light with Rev 3 (about which, more later) on Mary’s Tour Easy, both the front and rear lights began blinking erratically. Given that they have completely independent circuitry, this strongly suggests a power problem.

    Herewith, the headlight circuit voltage:

    Bafang headlight voltage - two 1 W running lights
    Bafang headlight voltage – two 1 W running lights

    The voltage should be a constant 6 or 6.3 V, depending on which description you most recently read. That is the case with only one light attached, so the problem occurs only when running both lights.

    The four pulses come from the amber LED’s Morse code “b” (dah-dit-dit-dit) with a 85 ms dits; the first dah pulse should be three times longer than the dits and definitely isn’t. The rear light’s red LED stays on continuously, except for two dark dits, so it draws a constant current and does not produce any changes in this trace.

    Both lights have 2.0 Ω sense resistors setting the LED current to 400 mA, which corresponds to 250 mA each from the Bafang controller’s 6.3 V headlight circuit. The headlight circuit’s total of 500 mA should work fine, although the “spec” seems to be basically whatever the OEM headlight requires.

    The Rev 1 amber light ran the LED at 360 mA with a supply current around 450 mA. That light and the rear light on the back ran fine, so the supply seems to have a hard maximum current limit at (a bit less than?) 500 mA.

    The least-awful solution seems to be backing off both LED currents to 360 mA to keep the total supply current well under 500 mA.

  • UPS SLA Battery Status

    UPS SLA Battery Status

    The UPS coddling the M2 printer began complaining about a bad battery, so I ran (nearly) all the UPS batteries through the tester:

    UPS SLA 2021-10-10

    The two blue flubs in the lower left come from the failed battery, with the dotted trace after charging to 13.7 V and letting the current drop to 20 mA.

    The red and green traces come from two other UPS batteries installed in 2016, with the dotted traces after charging similarly. The orange-ish trace is from the battery in a Cyberpower UPS bought in 2016, so it looks like all batteries of that vintage fade equally.

    Except for another pair of batteries in another UPS that had discharged stone cold dead; it may have been shut down and unplugged during a power outage and they never quite recovered.

    After five years, it’s time to refresh the fleet …

  • Bondhus Wrench Replacement

    Bondhus Wrench Replacement

    The Bondhus Lifetime Guarantee works, as a replacement wrench just arrived:

    Bondhus hex wrenches - 7-64 ball end - replacement
    Bondhus hex wrenches – 7-64 ball end – replacement

    A close look at the aligned tips suggests the defective wrench blank was mis-chucked in the machine cutting the ball end:

    Bondhus hex wrenches - 7-64 ball end - replacement - detail
    Bondhus hex wrenches – 7-64 ball end – replacement – detail

    All’s well that ends well: thank you, Bondhus!

  • Beverage Faucet Replacement

    Beverage Faucet Replacement

    The lesser kitchen faucet began dribbling and required replacement, as there are no user serviceable parts within. One of the 3D printed adapters I built during the previous iteration had disintegrated:

    Beverage faucet base plate adapter disintegration
    Beverage faucet base plate adapter disintegration

    The new faucet came with a somewhat different baseplate and I managed to conjure a firm, sealed mount from the various parts without further construction.

    The nicely curved brass snout is the third in my collection. Surely they’ll come in handy for something!

    While I was in a plumbing state of mind, I again replaced the spout O-rings in the never-sufficiently-to-be-damned American Standard Elite (hah!) faucet, as it was also dribbling.

    This time, I used oxalic acid to remove the assorted scale and crud inside the spout. It seemed to be more effective than the usual white vinegar, although nothing seems to preserve the O-rings.

  • Rail Trail: Fallen Tree Clearing

    Rail Trail: Fallen Tree Clearing

    We rolled up to a pair of walkers who had just watched a long-dead tree fall across the Dutchess Rail Trail ahead of them:

    Rail Trail - fallen tree - 2021-09-15
    Rail Trail – fallen tree – 2021-09-15

    Which is why I now carry a fold-out pruning saw in my tool kit:

    Rail Trail - fallen tree - cleared - 2021-09-15
    Rail Trail – fallen tree – cleared – 2021-09-15

    The mowing crew we encountered half a mile ahead had a chainsaw and cleared the remainder.

    Stay alert out there!

    Although I don’t have a picture, there was a freshly dead bat lying underneath the main trunk. I think it rode the tree down, only to get slapped hard against the gravel beside the trail. I’m sure bats power up faster than I do, but not quite fast enough.

  • Bondhus Wrench: Missing Ball

    Bondhus Wrench: Missing Ball

    Around the beginning of the year, I updated my collection of somewhat worn hex wrenches with a set of metric and inch ball-end hex wrenches from Bondhus sold by and shipped from Amazon:

    Bondhus hex wrenches - missing 7-64 ball
    Bondhus hex wrenches – missing 7-64 ball

    When I applied the 7/64 wrench to a setscrew, the missing ball came as a surprise.

    Even though the inch wrench set doesn’t get a lot of use, it’s possible I broke the ball off during a previous adventure, but a look at the end shows the black oxide coating covering the end:

    Bondhus hex wrenches - missing 7-64 ball - detail
    Bondhus hex wrenches – missing 7-64 ball – detail

    Yeah, it was born that way.

    I wonder if and how their lifetime guarantee works.

    [Update: It does!]

    Protip: as of this writing, the Amazon listing has two other “sizes” showing exactly the same set at significantly higher prices from two randomly named sellers:

    Bondhus hex wrench set - Amazon listing
    Bondhus hex wrench set – Amazon listing

    It is safe to assume Amazon no longer has its customers’ best interests in mind.

  • 1-by-One Folding Bluetooth Keyboard: Flex Cable Fix

    1-by-One Folding Bluetooth Keyboard: Flex Cable Fix

    Four years ago I got a folding Bluetooth keyboard for my then-newish Pixel phone:

    Folding keyboard - front
    Folding keyboard – front

    A few days ago, the 2 W S X Win keys stopped working, suggesting a problem with the matrix scan of that column.

    The trim cover over the fold on the back of the keyboard disengages from the hinge with gentle prying at the obvious places, exposing a flex cable pressed against a disturbingly right-angled edge:

    Folding keyboard - acute cable fold edge
    Folding keyboard – acute cable fold edge

    Unfolding the keyboard makes the acute bend against the case obvious, even though it’s hidden under the cable:

    Folding keyboard - failed cable - borrom view
    Folding keyboard – failed cable – borrom view

    Some tedious poking around with a continuity meter revealed not only a broken trace, but a crack in the flex cable:

    Folding keyboard - cracked flex conductor
    Folding keyboard – cracked flex conductor

    Protip: when you have nothing to lose, poke a pin through the flex cable into the trace to localize the break. The point leaves little holes, but so what?

    I scraped off the black coating and the insulation over the traces with an Xacto knife under the microscope, which definitely reveals my need for a tiny Waldo manipulator.

    Coating the exposed copper with solder and bridging the crack with one strand of the finest wire in my collection produced a truly horrific scene:

    Folding keyboard - patched flex conductors
    Folding keyboard – patched flex conductors

    The glop on the left is flux applied before soldering. The rugged terrain on the right is the exceedingly gummy adhesive holding the cable to the keyboard, which turned out to be surprisingly heat-sensitive.

    Fairly obviously, those patches will not survive much more flexing, so wrap the cable with Kapton tape and apply a stiffening layer of thick plastic tape:

    Folding keyboard - reinforced cable section
    Folding keyboard – reinforced cable section

    Apply more reinforcing tape and button it up again:

    Folding keyboard - reinforced cable flex edge
    Folding keyboard – reinforced cable flex edge

    I stuck the flex cable down with the repaired joint about a millimeter under that sharp edge, with double-sided sticky tape underneath to help immobilize the bruised area.

    While I had the covers off, I also reinforced the same section of the cable on the other side of the keyboard, in the hopes of preventing a crack.

    I have little faith in the long-term survival of this repair. Similar keyboards routinely emerge from the quantum froth of randomly named Amazon sellers, most of which have negative reviews reporting the failure of entire key columns; there’s no indication of any design improvement.

    The alert reader will have noted the cable has eight traces, enough for a 3×5 matrix of 15 keys, but the folding wing has 16 keys: the second row has four keys. I have no idea how they made that work, other than perhaps resistive coding for some of the keys.