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.

Author: Ed

Rehabilitating an Old Variac

Variac Rotor Before Fixup

Variac Brush Holder and Staking

Variac Rotor After Fixup

So I’ve had this ancient 5 A Variac on the heap for far too long, finally came up with an actual application, and discovered that not only was the line cord shot, it basically didn’t work.

Of course, I had to replace the cord & outlet before I discovered that it didn’t work…

The classic Variac failure happens when the carbon brush wears down to nothing, at which point the holder scrapes on the windings and the whole thing burns out. In this case, the brush still had 3/16″ left, but the sliding holder was firmly corroded in place.

I soaked it in PB’laster, rapped it all over with a small drift punch, and managed to drive the holder out. In the process, the brass sleeve around the brush holder came out, putting the entire problem on the bench.

The rotor had two brass rivets securing the brush contact bar (the part that’s connected to the actual brush holder by a length of copper braid) that would not come out, nohow. After I broke one off (the first picture), I found that they were swaged over on the bottom, so I broke the other one off and punched both stubs out.

I spent a few hours wearing a headband magnifier and gently filing everything to a pair of slip fits: brush holder into sleeve, sleeve into rotor. The rotor is aluminum, so I applied a liberal dose of oxidation inhibitor, slipped the sleeve in place, and staked that sucker down.

Which meant I spent another half hour filing the brush holder to restore the slip fit…

Turned out that the rivets were 40 mils, the holes were 43, and 00-90 machine screws are 43.5. I don’t have a 00-90 tap (mostly because I know I’d break it by looking hard at it), so I just ran a screw into the hole and formed the threads. They must have 10% engagement, tops, but this isn’t a high-stress application.

This is, I think, the first time I’ve ever used those 00-90 screws and nuts. The washers are 0-80 so they reach over the brush contact bar far enough to hold it in place. Dang, those things are small!

The main conduction path seems to be through a brass slip contact, into the aluminum rotor, through the brass sleeve, and into the carbon brush. I’m not convinced the rivets / screws conduct any appreciable amount of current to the contact bar and through the braid, but I shined up the contact patches anyway.

Put it all back together, fired it up, and it worked!

Ought to be good for the next half-century, at least…

2008-12-26
License to Laugh?

Washington DC License Plate

Found this one in a Hershey motel parking lot.

It turns out that these are official DC tags, not some weird protest movement’s idea of a good time!

http://dmv.dc.gov/serv/plates/tax.shtm

2008-12-26
Counterfeit Memory Stick from eBay

Bogus Memory Stick – Front

Last year I bought a “generic” Sony Memory Stick using eBay’s Bidding Assistant to get one of a whole bunch of similar items. Got it for a reasonable price, opened it up, and it turned out to be “too good to be true”: it looked to be a genuine Sony stick in sealed Sony packaging.

I checked the “how to identify a counterfeit Memory Stick” sites and concluded that it really was genuine, what with good printing and laser engraving. Sometimes these things happen; maybe the seller got a pallet of leftovers?

Bogus Memory Stick – Rear

It failed a few months later, I mailed it to Sony for a warranty replacement, they concluded it was a fake, and sent it back. Huh. Those cunning Chinese are getting really good at making fakes; maybe this was a “fourth-shift” product from the real Sony factory.

I contacted the seller, who said he sells “generic” products. I pointed out that “generic” means a second-tier manufacturer’s correctly labeled product, but that he sold a falsely labeled item. He offered a refund, I asked for money to cover my shipping, and he agreed. Knock me over with a feather.

So I sent it back and he actually refunded my money, plus shipping both ways. More feather toppling.

Sony Warranty Rejection

The term “fraud” did not enter the conversation, but I think he knew he was on thin ice and was willing to do whatever it took to make me Go Away.

From what I can tell, reporting this to eBay has no effect, because they already know and simply do not care.

2008-12-26
Database Follies
My “biz” (I use the term loosely) credit card statement had a $7.25 mystery charge from “NEWARK US CHICAGO IL”. I have done biz with Newark Electronics (and their HQ is in the Windy City), but not recently. Soooo, I gives ’em a call to ask WTF. Got passed from ear to ear, eventually reaching Jolanta in Credit Card Billing.

I described what I knew, she tapped in my credit card number, paused for a moment, then said “Oooooh, I know what happened!”

Turns out that they use “general account numbers” (or order numbers, or some such) for low-budget customers like me and that they recycle those numbers. A while ago it seems “the computer” started
1. Assigning some no-doubt-carefully-chosen general account number to the new transaction
2. Reaching into the database for, um, data
3. Sending the bill to the old account holder
Oops.

She says “the programmers are working on it right now” and she’ll refund the money muy pronto.

Wanna bet that a few somebodys got mystery charges for a few kilobucks apiece?

Uh-huh…
2008-12-26
Replacing a Refrigerator Bulb

Chandelier Bulb in Refrigerator

Subtitle: ya gotta have stuff!

Our refrigerator went dim; poking around inside revealed one of the two bulbs was dead.

It was obviously a replacement: both are 40-W flame-shaped bulbs that I bought for the chandelier that might still hang in 89 Burbank Road. I intended to leave them for the new owners, but they got swept up in the moving frenzy.

Being the sort of bear I am, I had written the replacement date on the bulb’s base: May 01. So that fancy bulb survived only six years!

Nothing lasts!

I picked the next-to-last flame-shaped bulb from the “Decorative Bulbs” box in the basement storage room, wrote the date on it (with a notation that the last one lasted 6 years), and screwed it in. Problem solved!

Being the sort of bear I am, I can do all that with a completely straight face…

2008-12-26
Bizarre Sink Styling

Or, perhaps, what were they thinking?

The lip around the sink works pretty well on the left side, but doesn’t stand a chance on the right.

Although it’s not visible here, there’s a nice water stain on the floor in the corner, plus the runoff you’d expect down the right side of the sink.

Nice styling, but …

2008-12-26
Door Chocks

Radial Arm Saw Setup

So I volunteered to make 40-odd door chocks for the Marching Band’s motel stay in Syracuse: by edict, all room doors must remain open until lights out. You’re probably not astonished to hear that the kids can think up all manner of reasons why their room doors just sort of drifted shut…

I contributed two battered maple library bookshelves (which my father salvaged from a flooded library three decades ago) to the cause, whacked ’em into 5-inch chunks, then ripped each chunk into two wedges. Being the sort of bear I am, I had those suckers immobilized every which way from zero, with a push stick to make sure nothing exciting happened near my knuckles.

Worked like a champ; nothing exciting happened at all. It just looks like the blade should suck the wedges into itself and fling ’em across the shop; they’re actually held in position from the outside and wind up quietly zinging against the blade without being caught.

I applied my cute little corner-rounding plane to one of the wedges, did some mental math, then came to my senses: Mr Chock, meet Mr Belt Sander. Ten minutes later, they’re all done!

A pleasant hour of shop time that made the whole basement smell of cut wood… which means that I’m breathing all those fine particles, even with the shopvac catching nearly everything else. Ran the lah-dee-dah radon reducer for a few hours, which helped a bit, and played with my upstairs toys for the rest of the afternoon.

2008-12-26