Category: Oddities

Who’d’a thunk it?

Mystery Not-Copper Line Cord

Harvesting a line cord for a widowmaker test setup revealed its inner secret:

Mystery not-copper wire – as found

The conductors are as thin as I’ve ever seen in an AC line cord, with 0.5 mm² = just under 20 AWG. The color code doesn’t match USA-ian standards, but neither does the labeling, so I’m not surprised.

If the individual strands seem unnaturally straight, they are, because they’re made of (presumably) copper plated on a (presumably) metallic core. Here’s what they look like after bending them sharply around my fingernail:

Mystery not-copper wire – bending

Wonderfully springy, utterly non-magnetic, and surprisingly durable.

Scraping the 0.02 mm strands with a sharp blade reveals a silvery interior, so it’s (presumably) not copper-coated plastic. Aluminum springs (ahem) to mind, but I’d expect tiny aluminum strands would snap (or at least deform) when bent and erode quickly when scraped.

Each wire measures about 1 Ω / m from the plug (a convenient 40 inch = 1 m away), which is the resistance you’d get from a single hair-fine 5 mil = 0.13 mm strand of 35 AWG solid copper. An 18 AWG aluminum wire would have the same resistance as a 20 AWG copper wire, both of which should be 32 mΩ / m: a factor of 30 less than this crap.

I have no idea what low-end Chinese factories use in place of copper, but it’s gotta be really cheap.

A hank of the wire goes into the Box o’ Springs, in the event I ever need a tiny straight spring rod; you definitely can’t wind this stuff into a coil! It might be fine enough for a crosshair / reticle, at least for crude optics.

2022-02-03
Euphorbia Horrida Flower

A Euphorbia horrida (one of the prickly plants) on the shelves just inside the front window burst into bloom:

Euphorbia Horrida – flowers

The flowery part looks unappetizing, but some critter must find the blooms attractive:

Euphorbia Horrida – flower – side

The small reddish balls look like the desert equivalent of nectar, as they’re viscous to the point of solidity:

Euphorbia Horrida – flower resin – top

I’m unwilling to experiment, but the resin ought to very sweet, lethally toxic, or wildly hallucinogenic. Maybe all three at once?

2022-01-22
Tektronix AM503: Q230 Dual JFET Replacement

Some suggested 151-1032-00 replacements obviously won’t work, such as Tekwiki’s 2N5397 single JFET. Bonding a pair into a single heatsink might suffice, but two separate cans generally aren’t identical enough for the purpose.

Curiously, Tekwiki also lists the 2N5911 as a 151-1032-00 replacement, which (being an actual dual JFET) looks more promising. This agrees with another cross-reference, although the “Sim[ilar] to” suggests considerable caution.

The 2N5911 pinout, as taken from its datasheet:

2N5911 Dual JFET pinout

The actual Tek 151-1032-00 can in its heatsink, oriented with the tab at the top (just visible to the right of the heatsink fin):

Tek 151-1032-00 – top view

Testing one side (with the tab on the left):

Tek 151-1032-00 test side A

And the other side (tab still on the left):

Tek 151-1032-00 test side B

A picture being worth a kiloword:

Tek 151-1032-00 – measured pinout

The drain and source over on the left side seem to be swapped compared to the 2N5911, although both gates are on the proper pins. This being a JFET, the source and drain may be electrically identical and it’s possible the tester labelled them backwards. The only way to be sure Tek wasn’t tragically clever is to poke around the PCB to figure out which pins connect to which other components.

So take a picture of the component neighborhood around the Q230 sockets:

PXL_20220105_210538214

Overlay it with a similar picture of the solder side, suitably reversed / recolored / transformed to match:

Tek AM503 – 151-1032-00 area – X-ray traces

The copper-side traces aren’t complete, as the red coloring marks only traces under the soldermask and omits bare solder-coated traces. Some traces on the component side run invisibly under parts. If I were doing it for money, not love, I’d pay more attention to the details.

Devote some time to tracing the traces and labeling the parts:

Tek AM503 – 151-1032-00 area – part IDs

Then doodle out the actual connections:

Tek 151-1032-00 – part connections

R246 shows Q230B lives in the left side of the can, because it’s connected between the B gate and B source pins, and confirms the tester swapped the B source and B drain pins. Whew!

R236 connects the B drain and the A source, confirming the pinout matches the 2N5911.

Comfortingly, the A side gate goes to all those other parts as it should.

So a 2N5911 will drop right into the Q230 socket with the proper pins going to the proper places. Whether it’s electrically Close Enough™ to the Tek spec, whatever it might have been, remains to be seen, but a good transistor circuit won’t depend too much on the actual transistor parameters.

2022-01-07

Blog Summary: 2021

The overall page view count may be down, but people have been replacing water heater anode rods at an increasing pace:

Home page / Archives	23775
Water Heater Anode Rod Access Done Right	8432
CNC 3018-Pro: GRBL Configuration	5301
G-Code and M-Code Grand Master List	5049
Why You Need a 6-Point Socket to Remove a Water Heater Anode Rod	4300
American Standard Elite Kitchen Faucet Disassembly	2621
Toyota Sienna: ABS Trouble Codes	2531
Raspberry Pi: Forcing VNC Display Resolution	2011
CNC 3018-ProXL: Y-axis Extension	1641
Subaru Forester Fuse Boxes	1276
Broom Handle Screw Thread: Replacement Plug	1239
Removing a Water Heater Anode Rod	1221
Auto-V.I.N Gauge Scam	1029
Low Budget Bench Power Supply	984
CNC 3018-Pro: DRV8825 Hack for 1:8 Microstep Mode	980
Kensington Expert Mouse Trackball: Scroll Ring Troubles	929
Whirlpool Water Heater “Lifetime” Warranty: The Good and the Bad	917
Digital Tattoo Power Supply: Polarity Doesn’t Matter	912
Bed Bugs: Thermal Kill	908
Review Phreesia Authorization	834
Huion H610Pro (V2) Tablet vs. Ubuntu 18.04	821
Kenmore 158.17032 Handwheel Clutch Disassembly	799
Shimano SPD Pedals: Creaking Resolved	788
2000 Toyota Sienna: Replacing the Bank 1 Sensor 2 Oxygen Sensor	753
Schwab / Symantec VIP Access vs. Yubikey	751
Toyota Sienna: Rear ABS / Speed Sensor Failure	729
HP-48GX Calculator Disassembly: Case Rivets	688
Reversible Belt Buckle: Post Restaking	683
Kensington Expert Mouse Scroll Ring Fix	629
Makerbot-style Endstop Power Adapter for Protoneer Arduino CNC Shield	616
Displaying Variables in Gnuplot	614
Kohl’s Guest WiFi Terms & Conditions: The Short Version	613
Replacing Phil Wood Hub Bearings	595
Magnesium Water Heater Anode Rod: Seven Years Later	576
Adding a Device to LTSpiceIV	564
Philips Sonicare Essence 5000: Battery Replacement	550
Browning Hi-Power Magazine Dimensions	545
MPCNC: Emergency Stop / Feed Hold / Resume Pendant	544
Raspberry Pi Interrupts vs. Rotary Encoder	538
CNC 3018-Pro: Home Switches	534
Resistance Soldering: Transformer	510
Adafruit Touch-screen TFT LCD Rotation	489
Quick-and-easy IR-passing / Visible-blocking Optical Filter	476
Dis-arming a Steelcase Leap Chair	471
Icecast and Ezstream Configuration	470
Why You Shouldn’t Use Heat Pumps in the Northeast US	465
Baofeng UV-5R Squelch Settings	460
Mini-Lathe Tailstock: Alignment	449
Homebrew Magnetizer-Demagnetizer	446
Arduino Serial Optical Isolator	444
Mysterious Noise in Toyota Sienna Minivan: Fixed!	444
Baofeng UV-5: Squelch Pop Suppression	434
bCNC Probe Camera Calibration	432
Demolition Card GTA 5-10-9	431
Multimeter Range Switch Contacts: Whoops!	425
Realigning Tweezer Tips	421
Schwalbe Marathon Plus and Michelin Protek vs. Glass Chip	418
Kenmore Model 158 Speed Control: Carbon Disk Replacement	417
Kenmore Electric Dryer: Power Resistor Replacement	416
Old Kenmore Sewing Machine Foot Control Repair	414
Closing the Dmesg Audit Firehose	400

Blog Page Views

That adds up to 200 k page views from 122 k visitors, for an average of 1.6 pages / visitor, down slightly from last year. For a variety of reasons, I wrote only 242 posts over the course of the year, so more folks read only the single post matching their search terms.

To give you an idea of how awful online advertising has become, WordPress shoveled 817 k ads at those readers, slightly more than four ads per view. Given the toxicity of online advertising, I just started paying $50/year for a “personal” plan to get a few more gigabytes of media storage, which also let me turn off the ads. Most of you won’t notice, as you already run ad blockers, but it will calm the results for everybody else.

Fortunately, losing the $250 / year income from those ads won’t significantly affect my standard of living.

2022-01-01

Christmas Bonus

An email arrived yesterday:

Subject: [redacted] review blog invitation about bluetooth programmer
Message: Hi dear,
Thanks for taking time to read this email.
I am Colleen from [redacted] brand, we sell two way radio on Amazon. I learned that you have wrote two way radio review blog before and I think your blog was written well.
Now we have a product named bluetooth programmer that need to be reviewed. […] We would like to invite you to write a review blog about it.
Your can earn $2 from each product sold! We promise it. Just put the link we provided you in your blog and the Amazon backstage will count the data. And we will pay you $2 for per product sold by your link through PayPal on the 30th of every month. (Please provide your PayPal account)
If you are willing to help us write a blog, please tell us if you have a radio and your address we will send you the product for free to review.
You can view more detailed information through this link:
[redacted]

Perhaps this “review” caught their eye:

Baofeng UV-5RE radio – overview

Or maybe it was my opinion of the Baofeng intermod problem?

Most likely, it’s just the result of an ordinary web search.

You might think everybody would know about Amazon’s crackdown on out-of-band review kickback scams, but either word hasn’t gotten around or the rewards still exceed the penalties. I think the latter applies, particularly when the offender (or its parent company) can spin up another randomly named Amazon seller with no loss of continuity.

“Earning” two bucks on a few purchases during the course of a year won’t move my Quality of Life needle, so I reported them to Amazon and that might be that.

For future reference, the chat with Amazon’s Customer Support rep produced a deep-ish link to their otherwise un-discoverable “Report Something Suspicious” page; the randomly named nodeld is a nice touch.

Speaking of randomly named sellers, it’s highly likely any Brand Name you remember from the Good Old Days has been disconnected from the tool / hardware / service you remember. Perusing a snapshot of the who-owns-who tool landscape as of a few years ago may be edifying: I didn’t know Fluke and Tektronix now have the same corporate parent.

Enjoy unwrapping your presents and playing with your toys …

2021-12-25
The Machine Stops

As foretold by E. M. Forster in 1909, we have two exhibits of the machine grinding to a halt.

Amazon sent one of their prescription savings cards, followed a few days later by a note:

We recently mailed you a physical copy of your Amazon Prime Rx savings card, and are writing to inform you that the BIN listed on your Prime Rx card printed incorrectly. The correct BIN is 019363.

So I wrote the corrected number on my card, not that I will ever use it:

Amazon RX – BIN error

Although the BIN (whatever that stands for) is a numeric value, it’s not treated as a number by whoever reads it. I’d lay money down that the source code’s formatting string changed from %6d to %06d or the equivalent in whatever fancy language they use nowadays.

The Social Security Administration sent me an email telling me to check a corrected version of a statement they sent a few months ago. Unfortunately, attempting to do so while writing this post produces a heads-up notice:

We apologize for any inconvenience accessing my Social Security. We are aware of some technical difficulties and are working on them at this time. We appreciate your patience as we work to solve the problems as quickly as possible.

Attempting to sign on seems to proceed normally, until this technical difficulty popped up:

We’re Sorry…
There has been an unexpected system error.
Your login session has been terminated. For security reasons, please close all of your internet browser windows.

The first statement put my nearest Social Security office 130 miles away in Wilkes Barre, PA. The corrected statement put it back where it belongs, in the hot urban core of Poughkeepsie.

Perhaps an off-by one error in the database lookup?

As far as I can tell, the world now depends on software nobody can understand or control.

2021-12-08
Halogen Blinky Test

Dropping the ordinary flashlight bulb into the drawer where it belonged revealed what I think is a halogen flashlight bulb, so I rebuilt the blinky test setup:

Halogen flashlight bulb test setup

This time I used a BUZ71A MOSFET (13 A, 100 mΩ RDS) driven with a 10 V gate pulse to make sure it acted like a switch instead of a current sink.

The first attempt looked … odd:

Halogen 3V – no cap – 4ms 1A-div

The gate pulse is yellow, the drain voltage is magenta, the bulb current is cyan at 1 A/div, and the timebase ticks along at 2 ms/div.

Moving the magenta trace to the supply voltage on the other side of the bulb produces even more weirdness:

Halogen 3V – no cap – Vsupply – 4ms 1A-div

Apparently, slugging a 3 A bench supply with a 3 A pulse lasting only 4 ms causes distress of the output tract.

Kludging a hulking 22 mF (yes, 22000 µF) cap across the power supply provides enough local storage to make things work properly:

Halogen 3V – 22000µF – Vsupply – 4ms 1A-div

With the cap in place, the drain terminal looks less unruly:

Halogen 3V – 4ms 1A-div

The drain voltage starts at about 600 mV with the 3 A pulse, a bit more than you’d expect from the alleged 100 mΩ drain-source resistance, but those numbers are generally aspirational and the test setup leaves a lot to be desired.

A 10 ms pulse produces a distinct flash, rather than a dull orange blip (timebase now at 10 ms/div):

Halogen 3V – 22000µF – 10ms 1A-div

A 30 ms pulse reaches full brightness as the filament settles at normal operating temperature:

Halogen 3V – 22000µF – 30ms 1A-div

A 20 ms flash might suffice for decorative purposes, in which case each pulse requires 90 mW·s = 3 V × 1.5 A × 20 ms of energy. Running it all day requires 7.8 kW·s = 2.2 W·h, so it’s even less appealing than that old skool tungsten bulb.

Which is, of course, why LED flashlight bulbs are a thing.

2021-12-07