A Crummy Commercial

When I needed a test lead, cord or cable at work (20th century) I would go over to a metal bracket screwed into the wall of the lab with closely spaced metal fingers like this one from Pomona: The cables and test leads were all hung by their connectors in the slots.  Usually finding the one you wanted meant taking out a bunch of other cables in front to get to it. But at home I either put cables in a box or draped them over a board I had cantilevered under my digital scope.  The scope sits on top of a bookshelf next to the bench.  This was fine until K9MMS gave me an idea to steal.  He had attached a horizontal board to his workbench shelving and added 3 drawer pull knobs to drape his various cordage onto that board, neat: I just happened to have a weird little unused thingy in the basement, kind of a combination of a small bookshelf and a board with 3 coat pegs.  I ripped the board with the pegs off the bookself, screwed it to a hunk of plywood and voila, cord ...

 Commercial power supplies again ?  Yes, one area where it's nice to use a commercial supply is for your electonics bench.  The built in metering and circuit protections are handy, you don't have to connect up yet another dvm or vom to the circuit under development. I purchased this HP 6281a supply: from where I used to work along with a bunch of other stuff, it was in pristine shape, must have been a spare used by the (Adar was a memory circuit board tester manufacturer) test engineers.  It remains THE item from that stuff that I still use on a daily basis and it works perfectly after 30 years.  It is spec'd at 0 to 7.5 volts (but works fine up to 9) at 5 A.  At the time (early 1990s) the low voltage supplies like the 6281a weren't valued as highly as the  others in the HP 62xx series that had higher output voltages, dual meters, dual voltages and so on.  As I recall I got it for less than $10. I keep the HP supply under the bench on top of a T...

 I found these Sprague Vitamin Q caps while looking through a parts drawer: Apparently they are still highly prized by our fellow travelers, musicians: https://www.theartoftone.com/new-old-stock-sprague-vitamin-qs-more/ Exactly why this is I'm not sure.  The "Vitamin Q" is apparently some proprietary oil used by Sprague to fill the cap (impregnant).  They are paper caps, oil filled, metal bodied with glass ends and are considered hermetically sealed.  Vitamin Q caps are supposed to be stable even at high/low temperatures and were prized for their longevity.   Incidentally hermeticity implies the use of metal, glass and/or ceramic as packaging materials.  Plastics are NOT considered hermetic packaging materials.  But due to the cost even the military uses commercial plastic devices in the 21st century.  The idea with modern plastics used in packaging ICs is that even if moisture gets in it won't foul up the works. I tried looking in several Allied ...

 One thing that I started building early during my time as an electronics enthusiast were power supplies.  With  transistorized radios and cassette recorders it was a pain to be buying batteries all the time.  Rechargeable batteries were available but expensive.  Also remembered that the GE Nicad Charger had a hinged cover because there was a *chance* of a explosive rupture of the cell during charge, yikes, that cover didn't inspire confidence. I can remember in high school getting directed by the librarian to a bunch of defunct wall warts in the library garbage can. Then it was just a matter of taking them home, figuring out how to open them up, changing the rectifiers and filter caps and adding 3 terminal regulators.  It was fun and I actually learned a lot. Here is a variable supply I made later out of an old Knight KG-240 tube amp: The supply is now in the garage and is used to power an old car radio.  I stripped off the high voltage windings from ...

 Here is a test fixture for 8 pin keyer chips that I still use daily even though it's old enough to vote: Started with a cut down Vector 3677-6 protoboard which has similar traces to a solderless prototype board. Then built a keyer circuit on the board (the PK-2):  http://wb9kzy.com/pk2a.pdf   However instead of a regular socket, used a ZIF (Zero Insertion Force) socket.  Also, made many of the connections: the timing capacitor C6, the output transistor Q1 and the voltage regulator U2 with pin sockets.  That way it's easy to test out other chips/transistors/capacitors without requiring a soldering iron.  A piece of cut down 2x4 softwood was used for the sides.  A saw kerf was cut into the wood to hold the circuit board.  Two aluminum plates were attached to the wood to hold everything together. (Drywall screws screwed into end grain !): The RCA jack on the side is a power output jack, the bracket originally held a switch so that's the reason for t...

 The Bureau of Labor Statistics operates a nice web page where a price and date of a historical item can be entered and the inflated price in today's dollars is revealed.  This makes for stunning reading as far as classic ham gear is concerned.   http://data.bls.gov/cgi-bin/cpicalc.pl   The most extreme example of this for ham radio is the Hallicrafters FPM-200 transceiver, per the 1963 Allied catalog on the World Radio History site: it sold for $2650, plugging that into the BLS calculator: which is $23,910 in December 2021  dollars !  As you might imagine it's a rare rig.  A teen making $1.15 per hour minimum wage in 1963 would have to work well over a year (2304 hours) to buy one and that doesn't include shipping ! Where do I use the BLS inflation calculator the most ?  on Ebay for bidding on items from my past that I can't really justify other than "I want one" An example was this Lionel 3270 Communications Lab that I was gifted for Christ...

One of my favorite circuit additions is putting a Light Emitting Diode (LED) in series with the positive input of an LDO (Low DropOut) voltage regulator: An LDO regulator will keep the output voltage constant even though the input voltage may only be a few tenths of a volt higher.  In addition, these regulators often have very low idle (aka quiescent) currents sometimes as little as 1 microamp.  Many ham radio projects that use a microcontroller have the capability to sleep, essentially stopping the clock or "heartbeat" of the chip until awakened by something like a key press for a keyer.  While sleeping the current is so low it's hard to measure.  Behold the amazing lack of power of unclocked CMOS. Adding the LED to the circuit allows the builder to take advantage of the LDO regulator's characteristics to provide a visual indication of current.  As shown in this video a keyer is "sleeping" at first, there is a barely visible crackle of light at the roughly ...

9V batteries and electronic projects First, holding a 9V battery securely is important, especially for portable gear.  Originally I'd use commercially sold clips like this stainless one from Keystone: But they are somewhat expensive and require some method of attaching them to the enclosure (here nailed into the top of a piece of wood on a test fixture) that won't have too high a profile and make the battery stick out of the holder.  Finally as can be seen with this steel cased alkaline battery, the metal clip will scratch the battery:     So I changed to a new method using a cable tie with a screw hole: Now a single 6-32 sized nut/bolt will hold the battery to the enclosure.  The cable ties are inexpensive (about a nickel each quantity 200 on Ebay) and will hold the battery in place without scratching the paint.  Also it's easy to change from horizontal to vertical orientation.  Note that 9V battery dimensions vary quite a bit so don't cinch the cable...

SMT refers to Surface Mount Technology which home builders shouldn't be afraid of.  I find that magnification along with good quality solder wick helps a lot.  One thing the builder may need is a way to hold parts in place while soldering them to a circuit board.   In industry this isn't usually a problem because solder paste is printed onto the board prior to placing the components.  This paste does "hold" the parts in place while they are being placed.  Then the board with mounted parts is heated until the solder melts.  One bonus is that the surface tension of the melted solder will align slightly misplaced parts.  But solder paste does have problems, mainly a finite shelf life, if not used before expiration the result is just a lump of solder stuck in a container.  Also sellers of solder paste like Digi-key will insist on rapid (expensive) shipment, the strong recommendation is to store it cold.  So I still use regular wire solder fo...