A Crummy Commercial

 I always try to twist the bare leads of a piezo together before mailing a kit, especially if the piezo is put in the same bag as the rest of the kit. bare leads twisted together (left side) Why ?  As seen here a piezo sounder is not only a speaker but can also function as a microphone: waveform of me yelling into a piezo And as seen here, if a piezo is rapped on a bench top it'll generate a substantial voltage of over 20 volts - don't want that applied to static sensitive parts. waveform of piezo brought down hard on bench AND, the piezo is a highly capacitive part, seen here measuring 63 nF (or .063 uF) the piezo measured at 63 nF , we don't want whatever charge is stored on that capacitor to be discharged into the other kit parts. Is shorting the leads together effective ?  I dunno, but most mechanical meter movements are stored/shipped with their terminals shorted together (also some VOMs have an off position that does the shorting), I figure it can't hurt to do the...

 Recently and probably as long as I can remember it's been the 2n7000 MOSFET (n-channel).  In the last week or two I've toasted a couple of them while working on the Wien Bridge audio oscillator.  This is from horsing the op-amp in and out of the solderless breadboard.   No, I wasn't wearing my static strap. But it wasn't like there was a lot of static discharging going on.   So I made up a sign and am placing it on the workbench to remind me: Also, for the Wien Bridge audio oscillator keying I tried a direct sub of a PN2222 for the 2n7000.  Looking at the flat marked side the 2n7000 leads are Source-Gate-Drain, the PN2222 leads are Emitter-Base-Collector.  It did work but as you can see there is an extended ramp down: PN2222 direct substitution for 2N7000 in keying circuit I then changed the ramp down cap from .1 uF to .018 uF and got this result: changed .1 uF cap to a .018 uF cap So replacing the MOSFET with a less susceptible to static damage NPN t...

 Does your soldering iron plug look like this: or like this: There is no way for an iron with the 2 wire plug to have a grounded tip. So an anti-static strap and mat may not be enough to prevent static damage when used with a 2 wire iron.  There could be mitigating factors with a "hardware store" iron like the Weller SP23, for example if the builder uses a wet sponge to wipe the tip maybe that discharges any static buildup ?    But what about the in-between time when the iron is being used ?  I think a grounded tip is the "suspenders and belt" solution. I modified my Weller SP23 2 prong iron with a ground wire connected to the tip via the mounting screws on the handle. The wire is Teflon - I didn't use a series 1 meg-ohm resistor maybe because I wasn't sure what might happen as it heated up.  The grounded Weller measures 2.4 kohms on my DVM from the tip to the banana plug.  One other mod was to wedge in a small, iron plated tip in place of the reg...

I heard a fellow on the air recently saying that he was shocking and being shocked by static discharge and that it seemed to affect him the most amongst his family.  To quote The Seekers song, Georgy Girl, "or is it the clothes you wear ?" - think natural fibers, natural materials.  Cotton or wool clothing and leather soled shoes may help prevent the static charge separation that vexes some more than others. One other item that will help prevent zapping our electronic stuff is an anti-static wrist strap. We used to use these 3M straps at GTE:    They are pretty standard, there is the fabric wrist strap, a 1 meg-ohm resistor located in the snap swivel and a long cord terminated with a banana plug for connecting to a grounded terminal.  Note that the banana plug is plugged into a medium sized alligator clip.  The actual wrist strap is elastic cloth which in my experience makes the strap worthless.  As time goes on the elastic degrades and there are time...

It's winter here with the dry air and the annoying static discharges.   But of course static charge buildup can damage modern electronics very quickly, here is my tale of woe from the turn of the century: I used to listen to the radio during the day using the (now discontinued) Morse Watch kit   as configured in this document .  I used a TEN-TEC RX-320 radio to listen to AM at 25 and 55 minutes past the hour.  During one winter day the RX-320 output came on and I started hearing an occasional loud popping sound from the speaker.  By the time I realized what was happening and turned the radio off/disconnected the antenna it was too late, the front end was damaged by static. I had been using the RX-320 with a 40 meter dipole, the popping sound must have been due to accumulated static charge finally reaching a high enough voltage to arc over.  The dipole was fed with RG-58 coax which would make for a potentially sizable high voltage capacitor at roughly ...