Repair Hacks

577 Articles

Burnt Resistor Sleuthing

October 15, 2023 by 7 Comments

You smell smoke and the piece of gear you are working on stops working, probably at an inopportune time. You open it up and immediately see the burned remains of a resistor. You don’t have the schematic, the Internet has nothing to say, and the markings on the resistor are burned away. What do you do? [Learn Electronics Repair] has some advice.

The resistor is probably open, but even if it isn’t, you can’t count on any measurement you make. The burning could easily change the value. The technique comes from comments on one of his earlier videos where he had such a burned resistor but was able to find the correct value. He decided to test the suggestion: cut away the burned resistor and measure the pieces that are left. It probably won’t give you the exact value, but it will get you in the ballpark.

So a rotary tool did the surgery, and you can see it all in the video below. We aren’t sure this method would work on every type of resistor you might encounter, and surface mount will also present special problems. However, if you are stabbing in the dark anyway, it won’t hurt to try.

Everyone knows the smoke that comes out is magic. Sometimes, you cut into components by necessity. Other times, it is for art’s sake.

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PCB Repair Is A Sticky Proposition

October 14, 2023 by 9 Comments

What do you do when a PCB is cracked or even broken in two? [MH987] has a plan: superglue the board back and then bridge the traces with solder, solder paste, or wire. The exact method, of course, depends on the extent of the damage.

We’ve had some success with similar techniques, and, honestly, for single-sided boards, we would be tempted to add a thin backer behind the crack. We’ve also used conductive paint to repair traces, but it’s good to have having as many tricks as possible because you never know what will work best for a particular repair. The post mentions that this is easier to do on a single-sided board, but it is certainly possible to do on a two-layer board.

The example repair is a Walkman which — if you are a youngster — was a portable music player that takes cassette tapes. These haven’t been made since 2010, so it is important to repair what you have.

If you can’t repair your Walkman, you could build an updated version. If your board is seriously damaged, you might get hope from this more extreme repair.

Blaupunkt Tube Radio Is The Sultan Of Radios

October 8, 2023 by 16 Comments

According to [M Caldeira], the Blaupunkt Sultan 24300 was one of the last tube radios made in the 1960s. He’s got one but it needed some tender loving care, and you can see how he approaches a restoration like this in the video below.

The radio was actually in better shape physically than most of the old radios we see. It wasn’t perfect, but it looked good on the outside. Electrically, though, it did need some work, and the dial had problems, too. The first obstacle was identifying exactly the model of the radio since there were a number of Sultan radios produced.

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Saving A Scope From The Dumpster

September 24, 2023 by 9 Comments

If you read Hackaday, you probably get the title of [SunEstra’s] post: A Casual Date with the Dumpster. Many great hacking projects start with finding one man’s trash. This June, [SunEstra] rescued an old Tektronix 2465B oscilloscope, which appeared to be in good shape. Why we never find four-channel 400 MHz scopes in the dumpster is hard to explain, but we are still happy for him, if not a little jealous.

As you might expect, powering up the scope was a disappointment. Relays clicked. Lights flashed. But no display. Adjusting the grid bias on the CRT brought up the display, but it also brought up something else: an error message.

The scope was complaining of “test failure 05-40.” A look through the manual reveals that is “positive level too positive.” Huh. Too much of a good thing, we guess. The test checks the A5 board, so a visual inspection there was the first step.

Unsurprisingly, there were electrolytic capacitors leaking electrolyte. This is, apparently, a well-known problem with this scope. Replacing the electrolytics with some similar tantalum capacitors. In a few cases, the corrosion had eaten pads off the PCB, and some were damaged during the removal. It took a little ingenuity to connect the new parts on the board.

The result? A working scope. Maybe the scope will help repair the next thing that comes out of the dumpster. Sometimes, the best dumpster dives involve intercepting the gear before it hits the dumpster. We keep hoping to run into one of these on the curb (the linked post seems dead, but the video is still there).

DIY Repair Brings An X-Ray Microscope Back Into Focus

September 22, 2023 by 6 Comments

Aside from idle curiosity, very few of us need to see inside chips and components to diagnose a circuit. But reverse engineering is another story; being able to see what lies beneath the inscrutable epoxy blobs that protect the silicon within is a vital capability, one that might justify the expense involved in procuring an X-ray imager.  But what’s to be done when such an exotic and expensive — not to mention potentially deadly — machine breaks down? Obviously, you fix it yourself!

To be fair, [Shahriar]’s Faxitron MX-20 digital X-ray microscope was only a little wonky. It still generally worked, but just took a while to snap into the kind of sharp focus that he needs to really delve into the guts of a chip. This one problem was more than enough to justify tearing into the machine, but not without first reviewing the essentials of X-ray production — a subject that we’ve given a detailed look, too — to better understand the potential hazards of a DIY repair.

With that out of the way and with the machine completely powered down, [Shahriar] got down to the repair. The engineering of the instrument is pretty impressive, as it should be for something dealing with high voltage, heavy thermal loads, and ionizing radiation. The power supply board was an obvious place to start, since electrostatically focusing an X-ray beam depends on controlling the high voltage on the cathode cup. After confirming the high-voltage module was still working, [Shahriar] homed in on a potential culprit — a DIP reed relay.

Replacing that did the trick, enough so that he was able to image the bad component with the X-ray imager. The images are amazing; you can clearly see the dual magnetic reed switches, and the focus is so sharp you can make out the wire of the coil. There are a couple of other X-ray treats, so make sure you check them out in the video below.

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Putting The Magic Smoke Back Into A Dodgy Spectrum Analyzer

September 12, 2023 by 3 Comments

The trouble with fixing electronics is that most devices are just black boxes — literally. Tear it down, look inside, but it usually doesn’t matter — all you see are black epoxy blobs, taunting you with the fact that one or more of them are dead with no external indication of the culprit.

Sometimes, though, you get lucky, as [FeedbackLoop] did with this Rigol spectrum analyzer fix. The instrument powered up and sort of worked, but the noise floor was unacceptably high. Even before opening it up, there was clearly a problem; in general, spectrum analyzers shouldn’t rattle. Upon teardown, it was clear that someone had been inside before and got reassembly wrong, with a loose fastener and some obviously shorted components to show for it. But while the scorched remains of components made a great place to start diagnosis, it doesn’t mean the fix was going to be easy.

Figuring out the values of the nuked components required a little detective work. The blast zone seemed to once hold a couple of resistors, a capacitor, a set of PIN diodes, and a couple of tiny inductors. Also nearby were a pair of chips, sadly with the markings lasered off. With some online snooping and a little bit of common sense, [FeedbackLoop] was able to come up with plausible values for most of these — even the chips, which turned out to be HMC221 RF switches.

Cleaning up the board was a bit of a chore — the shorted components left quite a crater in the board, which was filled with CA glue, and a bunch of missing pads. This called for some SMD soldering heroics, which sadly didn’t fix the noise problem. Replacing the two RF switches and the PIN diodes seemed to fix the problem, albeit at the cost of some loss. Sometimes, good enough is good enough.

This isn’t the first time [FeedbackLoop] has gotten lucky with choice test equipment in need of repairs — this memory module transplant on a scopemeter comes to mind.

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When Tail Lights Lose Touch With Reality

September 9, 2023 by 129 Comments

To study the history of the automobile is to also be a student of technological progress — as with each decade’s models come new innovations to make them better handling, more corrosion-resistant, faster, more efficient, or whatever the needs of the moment dictate. But sometimes that technological advancement goes awry and works against the motorist, making for a vehicle that’s substantially worse than what went before. [FordTechMakuloco] has a video with an example in a Ford pickup, which we believe deserves to be shared.

The problem with the vehicle was simple enough, indeed it’s one we’ve had in the past ourselves. Water got into a tail light, and corroded some connectors. The difference with this Ford though was that such a simple fault took out the whole car, and that the fix for a simple tail light cost $5600. The first was due to a vehicle-wide CAN bus going down due to the electrical short, and the second was due to the assembly containing an assortment of wiring and modules which couldn’t be replaced separately. These included some form of side-facing parking radar, a component unnecessary for operation of the light itself. Some relatively straightforward design and component supply decisions such as separating subsystems across multiple CAN busses, ensuring individual modules are separately available, and even designing connectors to face downwards and self-drain, could have fixed it, but the automaker chose instead to build in some planned obsolescence. Would you buy a Ford truck after seeing the video below the break?

We’ve written here before about how automotive design has taken this wrong path, and even advanced a manifesto as to how they might escape it. This Ford tail light seems to us an egregious example of electronics-as-the-new-rust rendering what should be a good vehicle into a badly designed piece of junk, and honestly it saddens us to see it. Oddly, there was once a time when a Ford truck was about as good as you could get.

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