Sunday, June 20, 2010


To check or test old-fashioned magnetic headphones use a very small battery, a 1.5V AAA cell is fine -- or just use an adaptor and plug them into your iPod. Important Note, if it says "Brush" or "Clevite" on your headphones, they are crystal headphones and will be ruined by any DC-type test. Check the label. Most Brush headphones have octagonal instead of cylindrical backs and a cast-in label.

Really old ones with tip plugs on the ends of the leads will often "click" just from touching the tips together in a damp palm. (The tip plating was porous -- so, brass, nickel, a little salt water, you get a current flow).

The adapter/iPod trick may be okay for even Brush-Clevite crystal headphones, I don't know and would not advise it. If you're an electronics type, a series condenser, say .01 or .05 mF, would make it safer. A 1:1 transformer might be even better -- 600:600 ohms, like a coupling transformer from an old modem, would do. (I've ruined a Brush earpiece plugging into the headphone jack on a reel-to-reel, so trust me and be careful).

Someone, malicious or ill-informed, is going around on eBay, asking headphone sellers to use a nine volt battery to "test" them. Please don't do this. It can do damage to some types. The wire used for the windings is tiny and can be melted by excessive current. Use a 1.5 Volt cell at most. Or use an ohmmeter; the current will be limited. Anything other than open or dead short indicates some degree of function.

Another thing -- if you're selling headphones on an auction site, why oh why would you unscrew the caps and take the diaphragms out? There's a permanent magnet in there, one with some oomph, and it will grab any little ferrous particles around. They'll get between the pole pieces and the diaphragm and make for trouble. The diaphragms themselves are a bit fragile; bend 'em and they are ruined. Last of all, the caps -- and often but not always the backs or "cups" -- are brittle Bakelite or hard rubber. They can chip, jam and break when unscrewed or dropped.

Be nice to old-style headphones. They will never make balanced-armature, mica-diaphraghm Baldwins (very complex inside) ever again. You will not find new Brush-Clevite cans (with their high-fidelity sound -- hams even used them as microphones) and the last stocks of Trimm "Commercial,*" "Professional*" and even the ubiquitous "Dependable" model ran out decades ago. What we have is all we'll have. Every set you break is gone. (But save the parts! Sometimes three broken sets add up to one working pair).

Related, Modern Radio Labs sells the definitive handbook on maintenance and repair of old headphones. It's worth owning.
* Highly recommended. My fave set of radio "cans" for years have been Commercials. Trimm's little "Featherweights" are nice, too.

Wednesday, June 16, 2010


I was taken with it at first sight; then I wondered if it was sacrilige. The USB Typewriter, though it is mildly invasive, doesn't ruin the function of the typewriter and should be reversible -- though I do wish he'd pad the platen:

I would not do this to a rare machine but as typewriter mods go, it is among the better. There are ways to slick it up (Pogo[tm] pins for the keybar contacts, for instance) but it's not bad.

Sunday, June 13, 2010


Someone hit this blog, looking for "Gerstner toolbox restoration." Interestingly, Gerstner is your best source for this; sure, their professional toolboxes are expensive, but they are selling quality and durability for that money -- and they stand behind their products. They offer an extensive array of replacement parts including felt lining, pulls, hinges, handles, locks, replacement keys and labels. This level of support is unusual for any product other than an automobile, industrial machinery or a major appliance and I think it's plain wonderful.

So, if you're out to restore your Gerstner toolchest, go the source!

Saturday, June 12, 2010


The author (?) calls it "The Pennsylvania Dutch Handbook" but you find examples anywhere you find old tools for sale.


There must be something about Thief River Falls, Minnesota.

I've known for years that modern-as-tomorrow RF switching manufacturer Dow-Key started U.S. operations there, building interesting and unusual semi-automatic telegraph keys, then branched out into coaxial relays, which eventually became the entire business. In 1966, they left Minnesota for California -- but that wasn't the end of the telegraphy connection for Thief River Falls.

In the early 1970s, then college student and amateur radio operator Ron Stordahl began selling an electronic speed-key kit, which he called a "Digi-Keyer." In the process, he found that a lot of hams and others were looking for a source of modern electronic components; in 1972, his home-town smaller-than-garage kit company became a fledgling parts house called Digi-Key and today, Dr. Ronald A. Stordahl is CEO of the fifth-largest electronic distributor in North America, the biggest employer in Thief River Falls.

In my career, I've seen their print catalog grow from a skinny magazine into something the size and heft of a big-city telephone book, small print, thin paper. No tubes but Digi-Key is Retrotechnologist-approved: like the famous mail-order outfits of yore, they carry a huge variety of items and are happy to sell to anyone. Orders go out the door the same day, too.

Both companies have sold parts in use from Kansas City to geosynchronous orbit. And it all started with telegraph keys. Twice!