[xsdb] had a real problem. His JBL L8400P 600 watt subwoofer went up in flames – literally. Four of the large capacitors on the board had bulged and leaked. The electrolyte then caused a short in the mains AC section of the board, resulting in a flare up. Thankfully the flames were contained to the amplifier board. [xsdb's] house, possessions, and subwoofer enclosure were all safe. The amplifier board however, had seen better days. Most of us would have cut our losses and bought a new setup. Not [xsdb] he took on the most extreme PCB repair we’ve seen in a long time.
After removing the offending caps and a few other components, [xsdb] got a good look at the damage. the PCB was burned through. Charred PCB is conductive, so anything black had to be cut out. The result was a rather large hole in the middle of an otherwise serviceable board. [xsdb] had the service manual for the JBL sub. Amazingly, the manual included a board layout with traces. Some careful Photoshop work resulted in an image of the section of PCB to be repaired. [Xsdb] used this image to etch a small patch board.
The amplifier and patch were milled and sanded to match up nearly perfectly. Incredibly, all the traces aligned. [Xdsb] soldered the traces across the join with small sections of wire and solder wick. After soldering in some new high quality capacitors, the amplifier was back in action!
If you’re a big fan of burned PCB’s, check out Hackaday Prize Judge Dave Jones latest EEVblog video, where he works on a Ness home alarm panel with a similarly cooked section of FR4.
[Thanks for the link JohnS_AZ!]
Lithium ion supercapacitors. No, not lithium ion batteries, and yes, they’re a real thing. While they’re astonishingly expensive per Farad, they are extremely small and used as the first line of defense in some seriously expensive heavy-duty UPS installations. Here’s a Kickstarter using these supercaps to replace the common AA, C, and D cell batteries. Even better, they can be recharged in seconds.
For each size battery, the caps used actually have a slightly higher energy density than a similarly sized dollar store battery. By adding a little bit of circuitry to drop the 3.8 Volts out of the cap down to the 1.5 V you expect from a battery, this supercap becomes a very expensive rechargeable battery, but one that can be recharged in seconds.
This is one of those crowdfunding campaigns we really like: an interesting tool, but something we just can’t figure out what the use case would be. These lithium ion supercaps are too expensive to be practical in anything we would build (save for a Gauss pistol), but the tech is just too cool to ignore. If you have a use case for these caps in mind, please leave a note in the comments.
Somewhat relevant Mouser link.
We’ve seen a few builds from the Flite Test guys before, like a literal flying toaster, airsoft guns mounted to planes, and giving an electric plane an afterburner (that actually produced a little extra thrust). Now the Flite Test crew is gearing up for the Flite Fest, an all things remote-controlled flight convention in Malvern, Ohio during the last weekend in July. Seems like a pretty cool way to spend spend a weekend.
Unless you get one of those fancy resistor kits where every value has its own compartment in a case or plastic baggie, you’ll soon rue the day your loose resistors become disorganized. [Kirll] has an interesting solution to hundreds of loose resistors: packaging tape. If you want a resistor, just grab a pair of scissors.
Okay, these Adafruit “totally not Muppets™” are awesome. The latest video in the Circuit Playground series is titled, “C is for Capacitor“. There’s also “B is for Battery“, because when life gives you lemons, light up an LED. Here’s the coloring book.
A few years ago, a couple of people at the LA Hackerspace Crashspace put together an animated flipbook device – something between a zoetrope and the numbers in those old electromechanical clocks – and launched a kickstarter. Now they’re putting on a show, presented by Giant Robot, featuring the animated art of dozens of artists.
Vintage electronics? Yes. Vintage Soviet electronics? Here’s 140 pages of pictures, mostly of old measurement devices.
The inductor is an often forgotten passive electrical elements used to design analog circuitry. [Charles's] latest proof of concept demonstrates how to measure inductance with an oscilloscope, with the hopes of making a PIC based LCR meter.
It is not that often one needs to measure inductance, but inductors are used in switching regulators, motor circuits, wireless designs, analog audio circuitry, and many other types of projects. The principles of measuring inductance can be used to test inductors that you have made yourself, and you can even use this knowledge to measure capacitance.
[Charles] originally saw a great guide on how to measure impedance by [Alan], and decided to run with the idea. Why spend over $200 on an LCR meter when you can just build one? That’s the spirit! Be sure to watch [Alan's] and [Charles's] videos after the break. What kind of test equipment have you built in order to save money?
Continue reading “The Beginnings of an LCR Meter”
[Moogle] wrote in to see if anyone can figure out why his unused electrolytic capacitors are popping. This is the behavior you see in populated caps whose electrolyte dries out. But these are still in his parts bin. Anyone know why they would pop when going unused?
We see a lot of BIOS flashing hacks; but it’s always a handy thing to know about when you get in a bind. Here [Adan] shows us how to reflash a corrupt BIOS using a Tiva C Launchpad board.
Wanting to hack together her own blow gun [Carlyn] scrapped a handheld vacuum cleaner. When she discovered the pump could not easily be converted from suck to blow she made a handheld suction manipulator which picks up paper plates and a few slightly heavier objects.
Unfortunately a drill press is not one of the tools we have in our lair right now. If we did, this tip about using it to help tap threads in a hole would come in really hand.
Retro computing fans will appreciate this Z80 computer build (translated). It’s a fairly large mainboard with plenty of chips, resistors, buttons, and seven segment displays. Excellent. [Thanks Daniel]
We start to drool a little bit when we see a teardown post that shows off a piece of equipment really well. We’ve already reached for a bib to catch the slobber from pawing our way through [David's] teardown of an HP 6010A bench supply.
In reaction to the other air gap flash unit we featured a few days ago, [Eirik] sent us a tip about another one he recently made. In his setup, the duration of the flash peak intensity is around 300ns (1/3,333,333 of a second). As a reminder, an air flash unit consists of a circuit charging a high voltage capacitor, a circuit triggering a discharge on demand, a high voltage capacitor and the air flash tube itself. The flash tube contains two wires which are separated just enough to not spark over at max potential. Isolated from the other two, a third wire is placed in the tube. This wire is connected to a trigger/pulse transformer, which will ionize the gap between the two capacitor leads. This causes the gap to breakdown and a spark to form, thereby creating a flash of light.
[Eirik] constructed his flash tube using an olive jar and a glass test tube. As you can see from the (very nice) picture above, the spark travels along the glass test tube, making the quenching much faster than in an open air spark. [Eirik] built his own high voltage capacitor, using seven rolled capacitors of roughly 2nF each made with duct-tape, tin foil and overhead transparencies. For ‘safety’ they are stored in a PP-pipe. A look at the schematics and overall circuit shown on the website reveals how skilled [Eirik] is, making us think that this is more a nice creation than a hack.
Disclaimer: As with the previous airgap flash, high voltages are used here, so don’t do this at home.
[Valentin] tipped us about his latest project: a homemade railgun. For the few that may not know already, a railgun is an electrically powered electromagnetic projectile launcher. It is comprised of a pair of parallel conducting rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail. [Valentin]‘s writeup starts with a detailed explanation of this principle, then a simple proof of concept is shown where a metal stick with two small round magnets on each end is accelerated along two alumium strips powered by a 9V battery.
The final build shown above is powered by a capacitor bank consisting of three 400V 2200uF capacitors in parallel. [Valentin] opted for a hot rail design, where the power is always present on the rails. The projectile is inserted into the assembly by a spring-loaded lever. A video is embedded after the break. If you found this interesting, you’re going to love the fully-automatic Gauss gun.
Continue reading “Building a Rail Gun”