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.

Category: Oddities

Who’d’a thunk it?

  • S-100 Bus Computer: Capacitor Reforming

    S-100 Bus Computer: Capacitor Reforming

    I volunteered to reform the hulking electrolytic capacitors in a long-unused S-100 Bus computer:

    S-100 Bus Cap Reforming - Codex 7200 Modem case
    S-100 Bus Cap Reforming – Codex 7200 Modem case

    Yes, it’s built into a recycled modem case. No, they don’t make modems like they used to, either. Regrettably, the five status indicators on the left were not set up as Der Blinkenlichten.

    The inside view:

    S-100 Bus Cap Reforming - inside view
    S-100 Bus Cap Reforming – inside view

    The multi-winding transformer in the back feeds bridge rectifiers (out of sight behind the caps) producing bulk DC:

    S-100 Bus Cap Reforming - bulk supply caps
    S-100 Bus Cap Reforming – bulk supply caps

    The gray cap is 52 mF = 52000 µF 15 V for the +5 V regulators supplying the TTL logic on each board.

    Two of the three blue caps (each 9 mF = 9000 µF 50 V) are for the +12 V and -12 V supplies. I think the third cap is a separate supply for a different purpose, but I did not trace out the wiring.

    The on-board regulators seem to use solid electrolyte caps that should still be in fine shape you should replace on principle, per ericlscott’s experience. You’d want to bring up each board separately while probing the voltages; the box of stuff accompanying the system has an extender card that should make probing easier.

    I hoped to boot the thing after restoring the caps, but a casual inspection showed wire corrosion:

    S-100 Bus backplane - jumper wire corrosion
    S-100 Bus backplane – jumper wire corrosion

    You’d want to pull the backplane out and replace those jumpers, as well as clean the bus contacts, before applying power.

    The system has two 8 inch floppy drives in a separate case with its own power supply:

    S-100 Bus floppy drives - overview
    S-100 Bus floppy drives – overview

    There was some corrosion in there, too:

    S-100 Bus Floppy Drive - optical sensor corrosion
    S-100 Bus Floppy Drive – optical sensor corrosion

    So I confined myself to reforming the caps and must let someone with more powerful motivation restore the rest of the system before trying to connect everything and booting CP/M.

    The general idea behind “reforming” an electrolytic capacitor is to regrow the oxide layer separating the anode and cathode electrodes, which involves passing a current of about 1 mA for as long as it takes to bring the terminal voltage up to the cap’s maximum rated voltage:

    S-100 Bus Cap Reforming - 52mF 15V
    S-100 Bus Cap Reforming – 52mF 15V

    That setup consists of an absurd number of PowerPole adapters putting the meter in series with a fuseholder repurposed to hold resistors to limit the current, with leads eventually ending up on the capacitor:

    S-100 Bus Cap Reforming - 52 mF 15 V cap connection
    S-100 Bus Cap Reforming – 52 mF 15 V cap connection

    The red dot is the overpressure vent, not a polarity marker.

    Apparently the Greek mu symbol wasn’t in the font available for the labels, as all the capacitors use m in its place: that capacitor is 52 mF = 52000 µF.

    The white plastic ejection handle belongs on the right end of the CPU board seen in the second picture, which was not plugged into its slot when I opened the case. I snapped the handle in place and plugged the board in just to keep it out of trouble. The case does not have board guide slots along the edges that would let the handle eject the board, but all that was definitely in the nature of fine tuning back then.

    I started with +15 V through a 16.9 kΩ resistor and swapped in 3.3 kΩ, 1 kΩ, and 220 Ω resistors as the cap voltage crept upward over the course of two days and eventually settled to a steady state:

    S-100 Bus Cap Reforming - 52mF 15V final voltage
    S-100 Bus Cap Reforming – 52mF 15V final voltage

    After discharging, the cap measured 59.5 mF with a 0.3 Ω ESR, which definitely seemed Good Enough.

    I reformed the three 9 mF 50 V caps at the same time by applying 50 V to three resistors captured on their screw terminals, changing the resistors as the voltages rose:

    S-100 Bus Cap Reforming - 50 V caps
    S-100 Bus Cap Reforming – 50 V caps

    Those three caps eventually measured (clockwise from upper right):

    • 9.66 mF, 1.0 Ω ESR
    • 9.76 mF, 2.6 Ω ESR
    • 10.46 mF, 3.4 Ω ESR

    The ESRs suggest they’re somewhat dried out, but I’d be tempted to run them anyway, because the on-board regulators should knock down the ripple.

    All of the reformed caps had leakage currents of a few hundred microamps. They’re not new capacitors and never will be, but they may be Good Enough.

    Getting the caps out of the diskette drive power supply required easing the entire supply frame / heatsink out of the case before unscrewing the capacitor clamps:

    S-100 Bus Cap Reforming - 16 mF 50V
    S-100 Bus Cap Reforming – 16 mF 50V

    That one eventually measured 22.1 mF with 0.14 Ω ESR. Its sibling, nominally 38 mF at 15 V, came in at 48.9 mF with 0.95 Ω ESR.

    The power supply PCB carries a handful of smaller aluminum electrolytic caps that are impossible to remove without unsoldering all the TO-3 transistor leads coming through the aluminum heatsink / frame, then completely dismantling the power supply:

    S-100 Bus floppy drives - power supply PCB
    S-100 Bus floppy drives – power supply PCB

    Although I reformed the big caps, I think a better plan would be to replace the whole thing with a contemporary switching supply. AFAICT it has 24 V and 5 V outputs; because we live in the future, dual-output switchers are cheap & readily available.

    And then I closed the cases to get them ready for the next part of their adventure …

  • Medicare Advantage Mail Merge: FAIL

    Medicare Advantage Mail Merge: FAIL

    A postcard arrived last week telling me to call a special number for special deals on Medicare Advantage plans. Being that type of guy, I managed to read the microscopic Fine Print and found this amusing blooper amid the disclaimers weasel wording:

    Medicare Advantage mail spam
    Medicare Advantage mail spam

    Inserting insurance carrier names should have happened before printing the card, so [CarrierA] and [CarrierB] are either placeholders or mail-merge variables.

    Also, you’re seeing the contrast-blown and magnified version of the postcard. The original Fine Print had faint orange ink on light green cardstock: colors having different hues with the same saturation and value to minimize legibility. In general, folks eligible for Medicare Advantage plans have trouble reading Fine Print, so the choice was not accidental.

    Not a compelling value proposition, as they say.

  • If Only I Were A Hotel

    Every few days this month, a Korean company has sent identical spam email messages to a series of plausible, albeit unused, addresses at softsolder dot com:

    As a forward-thinking hotel, we know you prioritize cleanliness and guest satisfaction.
    That’s why we’re excited to introduce Harington, an advanced sterilization device designed to provide
    99.99% bacteria and germ elimination for toilets, ensuring the highest standards of hygiene for your guests.

    Wikipedia reminds us Sir John Harington gets credit for inventing the flush toilet, thus explaining the device’s name. Surprisingly, a casual search with the obvious keywords suggests a different origin story much closer to the (nominal) company sending the spam.

    Another sentence definitely gained something in translation:

    A short but happy time spent on the toilet with a trustworthy friend who protects my secret and precious place from bacterial infection!

    The emails have an unsubscribe link, but experience shows clicking only encourages the senders.

    I wonder how much they spent to buy whatever list says my domain is a hotel …

  • Metallic Layered Paper

    Metallic Layered Paper

    With various iterations of the Letter sheet fixture in place, I made some layered paper “art” using metallic paper:

    Metallic layered paper - Pyrotechnics block
    Metallic layered paper – Pyrotechnics block

    That’s the Pyrotechnics quilt block pattern.

    This is the RGBY Subpixel pattern:

    Metallic layered paper - RGBY subpixels
    Metallic layered paper – RGBY subpixels

    The dotted rectangle in the lower left corner is the (turned off) front light in my low-budget light box and the glare in the upper left comes from the overhead basement LED strip lights.

    AFAICT, “metallic paper” consists of shiny aluminum film bonded to heavy paper / cardstock, with transparent colored film bonded atop the aluminum. The sheet is, of course, highly reflective, which looks dark unless it’s reflecting a bright surface, like the well-lit Sewing Room ceiling:

    Metallic layered paper - vs art paper
    Metallic layered paper – vs art paper

    I made the bright Pyrotechnics block in the upper left with art paper that looks bright & cheerful in any lighting:

    Metallic layered paper - art paper Pyrotechnics block
    Metallic layered paper – art paper Pyrotechnics block

    That’s the difference between specular reflectors and Lambertian reflectors.

    I cut the metallic paper face-down in the fixture:

    Pyrotechnics - metallized paper fixture
    Pyrotechnics – metallized paper fixture

    Although I’m underwhelmed by the metallic-layered-paper results, the stuff does make spectacular chaff:

    Letter paper fixture - on knife bars
    Letter paper fixture – on knife bars

    I should give our neighbor’s two-year-old lad a gift box …

  • Road Construction: Right Turn Only

    Road Construction: Right Turn Only

    The previous layout of Rt 376 had two lanes approaching the Raymond Avenue intersection from the south (from the right in this rotated & ruthlessly contrast-blown Google Maps screenshot):

    Rt 376 at Raymond - prior two-lane striping
    Rt 376 at Raymond – prior two-lane striping

    The right lane is marked Only ↱ for the Raymond intersection, starting just past the Vassar Security Office entrance in the top middle of the screenshot.

    Given this preliminary striping with faded Only ↱ markings, one might assume a similar lane layout is in effect for the new traffic circle at the intersection:

    Vassar Security Office Lane - A
    Vassar Security Office Lane – A

    The lighting poles may seem snugly placed, but not too much out of the ordinary:

    Some drivers seem concerned at this point:

    Vassar Security Office Lane - C
    Vassar Security Office Lane – C

    With any luck, they can swerve back into what is the only lane going all the way to the circle, because the right lane is dedicated to Vassar Security Office traffic:

    Vassar Security Office Lane - D
    Vassar Security Office Lane – D

    If you happen to be walking southbound, toward the traffic, in the middle of the shoulder beyond the turn lane, you will look that driver directly in the eye, as happened to me while walking back from Mary’s garden.

    As I mentioned last week, my money says that first lamp post, the one with the barrel guarding it, won’t survive the year.

    Given the utter lack of pedestrian facilities (f.k.a. “sidewalks”) south of the circle, I can only hope the road furniture will absorb all the damage / fatalities.

  • TEC Drawing Kit: Reconditioned Cover

    TEC Drawing Kit: Reconditioned Cover

    Our Young Engineer recently rebuilt the cover of a “vintage” drawing kit, with fabric pockets for protractors & scales and real leather hinges, thereby raising a long-procrastinated project to the top of my to-do list:

    TEC Drawing Set - top old
    TEC Drawing Set – top old

    I know my father used it when he took drafting after high school in 1929. His penmanship and drawing ability were up to par well before that.

    The inside sports a TEC logo:

    TEC Drawing Set - open old
    TEC Drawing Set – open old

    Some searching revealed it’s a No. 718 Drafting Set from the Technical Supply Company of Scranton and appeared in their 1913 catalog:

    TEC Brand Catalog p68
    TEC Brand Catalog p68

    The printing on the inside of the flap differs, but the logo has TEC in the middle.

    My father did not attend college and, in the teeth of The Great Depression, $26.50 was certainly too spendy for his family:

    CPI Calculator - 1929 to 2025
    CPI Calculator – 1929 to 2025

    When the catalog was printed in 1913, No. 718 cost the equivalent of $862.82. Nowadays, similar sets once again cost about twenty bucks on eBay, which tells you something about economics.

    None of that information changes what I know.

    Having recently touched a roll of Kraft-Tex while shelving some boxes, this seemed reasonable:

    TEC Drawing Set - top new
    TEC Drawing Set – top new

    It lacks pockets for the tools I’ve added:

    TEC Drawing Set - scales new
    TEC Drawing Set – scales new

    In retrospect, I should have used two leather snaps, but three would be excessive.

    I folded the Kraft-Tex flat across a steel scale to make the first folds around the base, then finger-crimped folds at the top of the base with subsequent crisping around the scale:

    TEC Drawing Set - open new
    TEC Drawing Set – open new

    The underside of the original case seemed stable:

    TEC Drawing Set - case bottom
    TEC Drawing Set – case bottom

    This may be sacrilege, but I saw no point in peeling the bottom just to cover it up,so I stuck the Kraft-Tex in place with a rectangle of adhesive sheet.

    It doesn’t look the same, but it still gives me a warm feeling.

    It still has the tiny wrench needed to adjust all its screws:

    TEC Drawing Set - wrench
    TEC Drawing Set – wrench

    It’s on 0.1 inch graph paper and is 40 mil = 1 mm thick, should you want to make your own. The blades taper down to essentially a knife edge, which is why it’s made from hard blue steel.

    I remember being fascinated by that little pig when I was a pup.

    Putting some scraps to good use, I stuck a cushion in the anvil for the next time I punch down a leather snap:

    Leather Snap kit - cushioned anvil
    Leather Snap kit – cushioned anvil

    The LightBurn SVG layout as a GitHub Gist:

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    view raw TEC Drafting Set cover – LightBurn layout.svg hosted with ❤ by GitHub
  • Road Construction: New Lamp Bases

    Road Construction: New Lamp Bases

    Seen in the equipment marshalling yard for the new traffic circle at the intersection of Raymond Avenue and Rt 376 / Hooker Avenue:

    Street Lamp Base - excavated
    Street Lamp Base – excavated

    The backstory:

    Apparently they excavated around the smashed bases and sawed off the conduits:

    Street Lamp Base - sawed conduit
    Street Lamp Base – sawed conduit

    Then they yoinked the concrete cylinders, installed new bases, re-connected the conduits, cast more concrete, and installed the posts:

    Street Lamp Base - Rombout House Ln - detail
    Street Lamp Base – Rombout House Ln – detail

    I think the two “Signal” box covers flush with the surface on either side of Rombout House Lane lie just beyond the edges of what will eventually be the repaved road at the intersection.

    Street Lamp Base - Rombout House Ln - overview
    Street Lamp Base – Rombout House Ln – overview

    Given how much damage the base at that intersection encountered, my visualization of the Cosmic All says that pole will not survive the year unless they install a few well-spaced bollards.

    There’s another pole on the other side of the road I expect will have a full-on collision, too.