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

  • Thing-O-Matic: HBP Connector Failure

    This has been a long time coming, as the connector shell over that pin connecting the MOSFET to the heater has been getting crispier despite my attention, cleaning, and occasional DeoxIT application.

    Burned-out HBP connector
    Burned-out HBP connector

    Notice that the burned pin now stands at a slight angle to the others. The PCB pad has no additional copper traces on that side to conduct the heat away from the failing connection, so the joint got hot enough to put the solder into its semi-liquid state, whereupon the springy connector rammed it upwards through the softened plastic shell. If the PCB fab shop used 60-40 lead solder, that’s around 188 °C. Silver solder would reach 220-ish °C. If the solder was eutectic, it would turn liquid and just drip off.

    What doesn’t show: the SMD pads that pulled free from the PCB surface, fortunately only under the rightmost three pins leading to the thermistor. Repairing the pads and connector makes no sense, so I think I’ll go with pigtail leads anchored to the plywood, with offboard connectors to reduce the strain on those pads. Powerpoles will be bulky, but maybe pigtails long enough to get them onto the case might work.

    As a general rule, soldering wires or connectors to SMD pads with no mechanical support is a Bad Idea and applying repeated mechanical stress to those connectors is a Very Bad Idea. Doing all that on a PCB running well over 100 °C with current right up near the connector’s absolute maximum, well…

  • Sony NP-FS11 Batteries: After the Aftermarket

    The batteries I rebuilt for our much-beloved Sony DSC-F505V camera back in early 2010 have faded away with constant use. Having already sawed the cases open, rebuilding three of them didn’t pose much of a challenge; this time I added a short tab of Kapton tape to help extract them from the camera socket.

    Rebuilt NP-FS11 batteries
    Rebuilt NP-FS11 batteries

    Three batteries seems to be about the minimax for ordinary use:

    • One in the camera
    • One in the carrying case
    • One in the charger

    You (well, we) can’t keep track of more than three: it always seems one battery gets overused and another gets lost in the dark. We’ll see how three works in practice; there’s a set of six more raw cells lying in wait.

    The new batteries produced these results on their first two charge-discharge cycles:

    Sony NP-FS11 2011 Packs - First Charges
    Sony NP-FS11 2011 Packs – First Charges

    One battery didn’t come up to speed on the first charge, but after that they’re all pretty close.

  • Ativa Cordless Phone Batteries

    These were cheap-after-rebate phones with 2/3 AA NiCd cells that lasted nigh onto five years. We rarely talk on the phone and even more rarely use these, so they’re on the dreaded continuous trickle charge and low usage cycle that kills rechargeable batteries. Of course, they’ve been sitting there for five years…

    The rebuild was no big deal, although I had to replace the original 360 mAh NiCd cells with 650 mAh NiMH cells (with tabs) because that’s what’s available nowadays. The trickle rate will be even lower relative to the capacity, of course, which may or may not be a Bad Thing.

    The packs contained a simple fuse consisting of a thinned section of the usual nickel strap connecting two cells, covered with a fiberglass sleeve under the shrink overwrap. For lack of anything smarter, I harvested the fuse and soldered it in the new pack. although the risk of a catastrophic short seems fairly low:

    NiCd pack with thin-wire fuse
    NiCd pack with thin-wire fuse

    The final result looks about as you’d expect, complete with obligatory Kapton tape wrap:

    Ativa phone - rebuilt battery
    Ativa phone – rebuilt battery

    The old pack is kaput and new pack delivers pretty nearly its rated capacity at an arbitrary 550 mA discharge (which is, admittedly, a bit stiff for the old pack):

    Ativa phone battery tests
    Ativa phone battery tests

    That takes care of one phone… the other one’s probably in the same condition, so I have enough cells to rebuild it, too.

  • Roof Shingle Fungus Redux

    Cleaned the gutters a while ago and the shingle fungus is getting worse: more sites and more stains. I sprized some general-purpose fungicide on the area over the kitchen:

    Shingle fungus - east slope
    Shingle fungus – east slope

    And down the valley between the north and east slopes:

    Shingle fungus - north and east slopes
    Shingle fungus – north and east slopes

    We’ll see what happens by next spring; I hope the larger moss clumps will take the hint.

    However, that short length of copper wire seems to be improving things. Here’s the before:

    Copper effect on roof discoloration
    Copper effect on roof discoloration

    Compared with the current state, from a different spot:

    Shingle fungus - below Cu wire
    Shingle fungus – below Cu wire

    The intense streaks have vanished, leaving a uniform lighter gray layer, and the upper area near the wire looks, mmm, less awful than the lower areas. I think running copper wire or zinc strips (which I have not found at the big box stores) along the ridge vent will do wonders, although I’m not sure how to anchor either one along the hip joints between the other slopes.

  • Weller EC1201A Soldering Handle Failure

    For the last few days, my trust Weller EC1000 soldering iron (well, station) has been misbehaving: shortly after cleaning the tip, it would become covered in charred residue and slag. Today, the LED I’d hacked across the heater terminals inside the base stayed dark, even though the tip was hot, and then became sensitive to the handle position. Obviously there’s a loose wire inside, right?

    So I took the handle apart by removing the two screws on the front plate:

    Weller EC1201A soldering handle innards
    Weller EC1201A soldering handle innards

    The trick to getting the guts out is to push down on the tab inside the handle that locks the cord strain relief block into the handle. After that, everything comes apart with very little force at all.

    Contrary to what I thought, the heater is in the tube surrounding the temperature sensor probe. Looking at the connector on the front of the base unit, the key is on the left side and the wires going clockwise from above the key are:

    • Yellow: heater
    • White: heater
    • Black: sensor
    • Red: sensor
    • Green: shield

    I would have sworn the red & black were the heater, as they have special-looking brass/bronze/copper colored pins & sockets. Wrong again.

    The temperature probe comes apart thusly:

    Weller EC1201A temperature probe disassembly
    Weller EC1201A temperature probe disassembly

    Basically, slide the connector and ceramic-coated sensor out of the back of the black shell, then pull the spring-loaded sheath out the front.

    I hoped for a laying-on-of-hands fix, but it was not to be: the tip heats while the LED (which I wired there early in the iron’s life) across the heater power remains off. But the LED blinked on intermittently with slight pressure on the iron’s tip; a bit more poking and prodding isolated an intermittent open-circuit to the ground wire just outboard of the strain relief at the handle:

    Soldering iron cable failure
    Soldering iron cable failure

    A bit more poking & tugging isolated an intermittent high-resistance short (a few hundred ohms, more or less) to a section of cable half a foot from the base connector at the bottom of the cable’s natural loop when the iron’s in the holder.

    Unfortunately, fixing all that didn’t restore the iron to life. It seems that the temperature sensor (a thermocouple?) has failed, allowing the tip to heat well beyond any rational temperature. Now that I’m looking, a cleaned solder layer turns blue with oxidation in a matter of seconds and rosin chars instantly. The temperature control knob has no effect whatsoever.

    The date codes inside the box show it’s been with me since late 1982, so on a dollars-per-year basis the thing has been a bargain. A new sensor is $60, a new handle is twice that, and I think it’s time for a new iron… at less than the price of the sensor alone, I think that’s OK.

  • Brita Pitcher Lid Hinge

    This pitiful excuse for a hinge actually lasted far longer than I expected:

    Brita pitcher lid hinge pins
    Brita pitcher lid hinge pins

    Also much to my surprise, the plastic solvent-bonded to itself, although I doubt either of those pins will survive another four years.

    The yellow discoloration seems to be most prominent on the inside of the lid, which suggests the water is nastier than they’d have you believe. The disinfection additive has switched from chlorine to chloramine and back to chlorine over the last few years, which may have something to do with it.

  • Digital Voltmeter Fuse Gotcha

    Measuring some low-value resistances with  one of my DVMs produced weird results: dead shorts around 10 Ω.

    Differential diagnosis:

    • Test lead tips clean
    • Wires firmly mounted in probes
    • Banana plugs OK
    • Short banana jumper across jacks reads 10+ Ω

    Took the meter apart and what do we see? An ABC ceramic fuse in good old PCB clips:

    DVM fuse holder
    DVM fuse holder

    Spinning the fuse dropped the resistance by a few ohms. Adding a minute drop of DeoxIT to each end, rotating the fuse to scrub it in, and wiping off the excess put the total resistance back around 0.2 Ω where it should be.