Vacuum Tube Repair After a Spectacular Failure

[Eric] has an Atwater Kent 55C AM radio from the early 1900’s. He’s been trying to restore the radio to proper working condition. His most recent pain has been with the rectifier tube. The tube is supposed to have a complete vacuum inside, but that’s not the case here. When the tube is powered up, it glows a beautiful violet color. It may look pretty, but that’s indicative that gas has leaked into the tube. It needed to be replaced.

[Eric] had a tube that would serve as a good replacement, but it’s plug didn’t fit the socket properly. He was going to have to use this old broken tube to make an adapter. Rather than just tearing the old tube apart, he decided to have some fun with it first. He hooked it up to a variac, an ammeter, and a volt meter. Then he slowly increased the voltage to see what would happen. The result was visually stunning.

The tube starts out with the same violet/blue glowing [Eric] experienced previously. As the voltage increases, it gets more and more intense. Eventually we start to see some green colors mixing in with the violets. [Eric’s] reaction to this unexpected result is priceless. As the tube gets increasingly hot, the anode starts glowing an orange-red color. Finally, the filament starts to crackle like a sparkler before the tube just gives up and completely fails.

After the light show, [Eric] moves on to replacing the tube. He begins by tapping on the old tube’s socket with the end of a screwdriver. After much tapping, the glass starts to come lose from the socket. After a bit of wiggling and twisting the tube finally came free from the socket. [Eric] luckily had an unused octal socket that fit perfectly inside of the old socket. All he needed to do to build his adapter was to connect the four pins from the old adapter to the proper pins on the octal socket. Piece of cake.

…Or so [Eric] thought. After testing some new tubes with a tube tester, he realized he had soldered all four pins incorrectly. On top of that, he had super glued the adapter together. He eventually got the two pieces apart. This time he removed all of the unused pins from the octal socket so he wouldn’t get it wrong. Another run on the tube tester confirmed that everything looked good. After plugging the tube into the radio, it worked just as expected

If you need fabrication rather than repair, we’ve got you covered there as well. Check out [Charles Alexanian’s] process for making new vacuum tubes in his garage. Now if you just have too darn many of them around, you can always decorate your pad with ‘em.

Continue reading “Vacuum Tube Repair After a Spectacular Failure”

Fixing a Broken Postage Scale

[Starhawk] had an old Pitney Bowes G799 postage scale that wasn’t working as it should. After years of faithfully measuring packages and cooking ingredients, the scale stopped working. At first it fell out of calibration. Then the power up sequence stopped working. The scale normally would turn on, light up the entire display, then change to dashes, and finally set itself to 0.0 lbs. In this case, it would get stuck at the dashes and never change to 0.0.

[Starhawk] ended up purchasing another duplicate scale from eBay, only to find that when it arrived it had the exact same power up problem. Using deductive reasoning, he decided that since the scale was broken during shipping the problem would likely be with a mechanical component. He turned out to be correct. The cheap momentary power button was at fault. When pressing the button, the contact would get stuck closed preventing the scale from zeroing out properly. [Starhawk] easily fixed his problem by replacing the switch.

Next [Starhawk] replaced the old scale’s LCD module with one from the new scale, since the old one looked to be on its way out. The scale still had a problem correctly measuring weight. [Starhawk] tried swapping the load cell from the new scale to the old one, but he found that the new load cell had some kind of problem that prevented the scale from zeroing out properly. The solution ended up being to use the newer “analog board” as [Starhawk] calls it.  The end result was the old scale with two newer circuit boards, an older load cell, and a new power switch. Next time it might be easier to just build his own scale.

A New Handle For An Old Soldering Station

About 20 years ago, [Simon] spent a few week’s pay on a soldering station, a Micron W/2172. It served him well for the past few decades, but lately he hasn’t been able to find a supply of new tips for it. The Micron went into a cupboard and he upgraded to a newer Hakko soldering station.

The old Micron was still sitting in the cupboard when [Simon] realized both stations use a 24V supply for the heater, and you can buy replacement Hakko handle for a few bucks. Having two soldering stations would be handy, so [Simon] set out to convert the old Micron station to accept Hakko handles.

The only technical challenge for this modification was to figure out how the old circuit board in the Micron would read the thermistor  in the new handle. The original circuit used a dual op-amp, with one side used to amplify the thermocouple and the other to compare it to the temperature set point. After measuring the set point and a bit of Excel, [Simon] had a small circuit board that would replace the old op-amp. After that it was only a matter of wiring the new handle into the old station, calibrating the temperature settings, and enjoying the utility of two soldering stations.

Faulty ESP8266s Release Smoke, Then Keep Working?

[Ray] is in a bit of a pickle. All appeared well when he began selling an ESP8266-based product, but shortly thereafter some of them got hot and let the smoke out. Not to worry, he recommends ignoring the problem since once the faulty components have vaporized the device will be fine.

The symptom lies in the onboard red power indicator LED smoking. (Probably) nothing is wrong with the LED, because upon testing the batch he discovered its current limiting resistor is sometimes a little bit low to spec. Off by a hair of, oh, call it an even 1000x.

HAD - HotESPY3Yep, the 4700 ohm resistor is sometimes replaced with a 4.7 ohm. Right across the power rail. That poor little LED is trying to dissipate half a watt on a pinhead. Like a sparrow trying to slow a sledgehammer, it does not end well. Try not to be too critical, pick ‘n place machines have rough days now and then too and everyone knows those reels look practically the same!

The good news is that the LED and resistor begin a thermal race and whoever wins escapes in the breeze. Soon as the connection cuts the heat issue disappears and power draw drops back to normal. Everything is fine unless you needed that indicator light. Behold – there are not many repairs you can make with zero tools, zero effort, and only a few seconds of your time.

[Ray] also recommends measuring and desoldering the resistor or LED if you are one of the unlucky few, or, if worst comes to worst, he has of course offered to replace the product too. He did his best to buy from authentic vendors and apologizes to the few customers affected. As far as he knows no one else has had this problem yet so he wanted to share it with the community here on Hackaday as soon as possible. Keep an eye out.

If you have never seen smoke ISO9001-certified electronics repair before, there is a short video of this particular disaster upgrade caught live on tape after the break.

Continue reading “Faulty ESP8266s Release Smoke, Then Keep Working?”

Repairing and Reviewing a 1976 PONG Clone

Hackaday alum [Todd] has been searching for an old PONG clone for the last two years. This variant is called, “The Name of the Game”. [Todd] has fond memories of playing this game with his sister when they were young. Unfortunately, being the hacker that he is, [Todd] tore the game apart when he was just 14 to build his own Commodore 64 peripherals. He’s been wanting to make it up to his sister ever since, and he finally found a copy of this game to give to his sister last Christmas.

After opening up the box, [Todd] quickly noticed something strange with the power connector. It looked a bit charred and was wiggling inside of the enclosure. This is indicative of a bad solder joint. [Todd] decided he’d better open it up and have a look before applying power to the device.

It was a good thing he did, because the power connector was barely connected at all. A simple soldering job fixed the problem. While the case was still opened, [Todd] did some sleuthing and noticed that someone else had likely made repairs to several other solder joints. He also looked for any possible short circuits, but everything else looked fine. The system ended up working perfectly the first time it was started.

The end of the video shows that even after all this time, simple games like this can still capture our attention and be fun to play for hours at a time. [Todd] is working on part 2 of this series, where he’ll do a much more in-depth review of the system. You can watch part 1 below. Continue reading “Repairing and Reviewing a 1976 PONG Clone”

Repairing Burnt Speakers with a Steady Hand

[Martin] seems to have a knack for locating lightly damaged second-hand audio gear. Over the years he’s collected various types of gear and made various repairs. His most recent project involved fixing two broken tweeter speakers.

He first he needed to test the tweeters. He had to remove them from the speaker cabinet in order to gain easier access to them. The multimeter showed them as an open-circuit, indicating that they had likely been burned. This is an issue he’s seen in the past with this brand of speaker. When too much power is pumped through the speaker, the tiny magnet wire inside over heats and burns out similar to a fuse.

The voice coil itself was bathing in an oily fluid. The idea is to help keep the coil cool so it doesn’t burn out. With that in mind, the thin wire would have likely burned somewhere outside of the cooling fluid. It turned out that it had become damaged just barely outside of the coil. [Martin] used a sharp blade to sever the connection to the coil. He then made a simple repair by soldering the magnet wire back in place using a very thin iron. We’ve seen similar work before with headphone cables.

He repeated this process on the second tweeter and put everything back together. It worked good as new. This may have ultimately been a very simple fix, but considering the amount of money [Martin] saved on these speakers, it was well worth the minimal effort.

Repairing A Router Plagued By Capacitors

[psgarcha]’s modem/router comes straight from his internet provider, is on 24/7, and is built with the cheapest components imaginable. Eventually, this will be a problem and for [psgarcha], this problem manifested itself sooner than expected. Fortunately, there was a soldering iron handy.

The problems began with a boot loop – starting the router up, watching the blinking LEDs, and watching these lights follow the same pattern forever. Initially thinking this would be a problem with the firmware, [psgarcha] did the only thing he could do – take it apart. Inside, he found some bulging capacitors. Unsheathing his iron and replacing the obviously faulty components, [psgarcha] plugged the router in and had everything work. Great. Until those caps failed again a few months later.

There was obviously something wrong with the circuit, or wrong with the environment. Figuring it was hot out anyway, [psgarcha] replaced those caps again and added a fan and a small heatsink to the largest chip on the board. This should solve any overheating problems, but the real testing must be done in summer (or putting the router in a well-insulated enclosure). It’s an easy fix, a good reminder of exactly how often caps fail, and a great example of reducing the electronic cruft building up in landfills.