Faulty Electrolytic Caps Don’t Always Look Bad

July 18, 2021 by Donald Papp 49 Comments

Old electrolytic capacitors are notorious for not working like they used to, but what exactly does a bad capacitor look like, and what kinds of problems can it cause? Usually bad caps leak or bulge, but not always. In [Zak Kemble]’s case, a bad cap caused his Samsung HT-C460 Home Cinema System to simply display “PROT” then turn itself off. Luckily, replacing the troublesome cap fixed everything, but finding the problem in the first place wasn’t quite so straightforward. A visual inspection of the device, shown open in the photo above, didn’t reveal any obvious problems. None of the capacitors looked anything out of the ordinary, but one of them turned out to be the problem anyway.

The output cap had developed an internal short, but visually looked fine.

The first identifiable issue was discovering that the -5 V supply was only outputting about -0.5 V, and there was a 6 V drop across two small 0805-sized resistors, evidence that something was sinking far more current than it should.

Testing revealed that the -5 V regulator wasn’t malfunctioning, and by process of elimination [Zak] finally removed the 470 uF output capacitor on the -5 V output, and the problem disappeared! Inspecting the capacitor revealed no outward sign of malfunction, but it had developed an internal short. [Zak] replaced the faulty cap (and replaced the others just to be safe) and is now looking forward to getting years more of use out of his home cinema system.

When a PSU gives up the ghost, bad capacitors are almost always to blame, but we’ve seen before that it’s not always easy to figure out which ones are bad. One thing that helped [Zak] plenty in his troubleshooting is finding a full schematic of the power supply, just by doing a search for the part number he found on it. A good reminder that it’s always worth throwing a part number into a search engine; you might get lucky!

Repair Hack Saves Tesla Owner From Massive Bill

July 16, 2021 by Dan Maloney 74 Comments

As expensive as a new car is, it almost seems like a loss leader now to get you locked into exorbitantly expensive repairs at the dealership’s service department. That’s the reason a lot of us still try to do as much of the maintenance and repairs on our cars as possible — it’s just too darn expensive to pay someone else to do it.

Case in point: this story about a hapless Tesla owner who faced a massive repair bill on his brand new car. [Donald]’s tale of woe began when he hit some road debris with his two-wheel-drive Model 3. The object hit penetrated the plastic shield over the front of the battery pack, striking a fitting in the low-pressure battery cooling plumbing. The plastic fitting cracked, causing a leak that obviously needed repair. The authorized Tesla service center gave him the bad news: that he needed a new battery pack, at a cost of $16,000. Through a series of oversights, [Donald]’s comprehensive insurance on the car had lapsed, so he was looking at funding the repair, approximately half the cost of a new Model 3, out of pocket.

Luckily, he got in touch with [Rich Benoit] of The Electrified Garage, one of the few independent garages doing Tesla repairs and customizations. The video below is queued up to the part where they actually do the repair, which is ridiculously simple. After cutting off the remains of the broken fitting with a utility knife, [Rich]’s tech was able to cut a thread in both the fitting and the battery pack, and attach them together with a brass nipple from the plumbing section of the local home store. The total bill for the repair was $700, which still seems steep to us, but a far cry from what it could have been.

Hats off to [Rich] and his crew for finding a cost-effective workaround for this issue. And if you think you’ve seen his EV repairs before, you’re right. Of course, some repairs are more successful than others.

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Chip Transplant Brings Timex 2048 Back From Grave

July 12, 2021 by Tom Nardi 16 Comments

The 1984 Timex Computer 2048 that [Drygol] recently got his hands on was in pretty poor shape. Not only did it have the mangled exterior that comes from several decades of hard use and furious typing, but the internals appeared to be shot as well, with the machine showing nothing but vertical lines when powered up. Thankfully, this retro computer virtuoso was more than up to the challenge of bringing it back from the brink.

After a good cleaning and the installation of a reproduction front panel, the Timex was already looking much better. Unfortunately [Drygol] says he doesn’t currently have the equipment necessary to touch up the graphics and lettering on the key caps, but the fact that he had to qualify that statement with “currently” has us all sorts of excited to see what he’s planning down the line.

Of course beauty is only skin deep, and this particular TC-2048 was still bad to the bone. [Drygol] had a hunch its Z80 processor was dead, but after swapping it and its socket out, the machine still wouldn’t start. Though he did note that the garbled graphics shown on the screen had changed, which made him think he was on the right track. He then replaced all the RAM on the board, but that didn’t seem to change anything.

There isn’t a whole lot else to go wrong on these old machines, so the final step was to try and replace the ROM. Sure enough, after installing a new Winbond W27C512 chip with the appropriate software burned onto it, the nearly 40 year old computer sprang back to life.

Another classic computer saved from the trash heap, but it’s all in a day’s work for [Drygol]. Over the years we’ve seen him perform meticulous repairs on computer hardware that any reasonable person would have given up on. Even if you’re not into retro hardware, his restorations are always full of fascinating tips and tricks that can be applied when repairing gadgetry from whatever era happens to tickle your fancy.

Steady Hand Brings GBA Cart Back From The Grave

June 22, 2021 by Tom Nardi 15 Comments

The flash chips used in Game Boy Advance (GBA) cartridges were intended to be more reliable and less bulky than the battery-backed SRAM used to save player progress on earlier systems. But with some GBA titles now hitting their 20th anniversary, it’s not unheard of for older carts to have trouble loading saves or creating new ones. Perhaps that’s why the previous owner tried to reflow the flash chip on their copy of Golden Sun, but as [Taylor Burley] found after he opened up the case, they only ended up making the situation worse.

A previous repair attempt left the PCB badly damaged.

When presented with so many damaged traces on the PCB, the most reasonable course of action would have been to get a donor cartridge and swap the save chips. But a quick check on eBay shows that copies of Golden Sun don’t exactly come cheap. So [Taylor] decided to flex his soldering muscles and repair each trace with a carefully bent piece of 30 gauge wire. If you need your daily dose of Zen, just watch his methodical process in the video below.

While it certainly doesn’t detract from [Taylor]’s impressive soldering work, it should be said that the design of the cartridge PCB did help out a bit, as many of the damaged traces had nearby vias which gave him convenient spots to attach his new wires. It also appears the PCB was designed to accept flash chips of varying physical dimensions, which provided some extra breathing room for the repairs.

Seeing his handiwork, it probably won’t surprise you to find that this isn’t the first time [Taylor] has performed some life-saving microsurgery. Just last year he was able to repair the PCB of an XBox controller than had literally been snapped in half.

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Restoring A Vintage Tube Tester To Its Former Glory

June 9, 2021 by Tom Nardi 38 Comments

It can be difficult for modern eyes to make much sense of electronics from the 1960s or earlier. Between the point-to-point soldering, oddball components, and the familiar looking passives blown up to comical proportions like rejected props from “Honey, I Shrunk the Kids”, even experienced hardware hackers may find themselves struggling to understand what a circuit is doing. But that didn’t stop [Cat0Charmer] from taking the time to lovingly restore this Hickok Cardmatic KS-15874-L2 tube tester.

The good news was that the machine had nearly all of its original parts, down to the Hickok branded tubes in the power supply. Unfortunately it looks like a few heavy handed repairs were attempted over the years, with a nest of new wires and components intermixed with what [Cat0Charmer] actually wanted to keep. The before and after shots of individual sections of the machine are particularly enlightening, though again, don’t feel to bad if you still can’t make heads or tails of the cleaned up version.

Hiding new capacitors inside of the old ones.

As you’d expect for a machine of this age, many of the original components were way out of spec. Naturally the capacitors were shot, but even the carbon composition resistors were worthless after all these years; with some measuring 60% away from their original tolerances.

We particularly liked how [Cat0Charmer] hollowed out the old capacitors and installed the new modern ones inside of them, preserving the tester’s vintage look. This trick wasn’t always feasible, but where it was applied, it definitely looks better than seeing a modern capacitor adrift in a sea of 60’s hardware.

After undoing ham-fisted repairs, replacing the dud components, and installing some new old stock tubes, the tester sprung to life with renewed vigor. The previously inoperable internal neon lamps, used by the tester’s voltage regulation system, shone brightly thanks to all the ancillary repairs and changes that went on around them. With a DIY calibration cell built from the schematics in an old Navy manual, [Cat0Charmer] got the tester dialed in and ready for the next phase of its long and storied career.

We love seeing old hardware get restored. It not only keeps useful equipment out of the scrap heap, but because blending new and old technology invariably leads to the kind of innovative problem solving this community is built on.

Riding Mower Repair Uncovers Miniature Culprit

June 4, 2021 by Tom Nardi 62 Comments

Most people would be pretty upset it the lawn mower they spent $4,000 USD on had a major failure within the first year of owning it. But for [xxbiohazrdxx], it was an excuse to take a peek under the hood and figure out what brought down this state-of-the-art piece of landscaping gear.

It should be said that, at least technically, the Husqvarna TS 348XD in question was still working. It’s just that [xxbiohazrdxx] noticed the locking differential, which is key to maintaining traction on hilly terrain, didn’t seem to be doing anything when the switch was pressed. Since manually moving the engagement lever on the transmission locked up the differential as expected, the culprit was likely in the electronics.

As [xxbiohazrdxx] explains, the switch on the dash is connected to a linear actuator that moves the lever on the transmission. The wiring and switch tested fine with a multimeter, but when the actuator was hooked up to a bench power supply, it didn’t move. Even more telling, it wasn’t drawing any power. Definitely not a good sign. Installing a new actuator would have solved the problem, but it was an expensive part that would take time to arrive.

Repairing the dead actuator seemed worth a shot at least, so [xxbiohazrdxx] cracked it open. The PCB looked good, and there were no obviously toasted components. But when one of the internal microswitches used to limit the travel of the actuator was found to be jammed in, everything started to make sense. With the switch locked in the closed position, the actuator believed it was already fully extended and wouldn’t move. After opening the switch itself and bending the contacts back into their appropriate position, everything worked as expected.

A tiny piece of bent metal kept this $4,000 machine from operating correctly.

As interesting as this step-by-step repair process was, what struck us the most is [xxbiohazrdxx]’s determination to fix rather than replace. At several points it would have been much easier to just swap out a broken part for a new one, but instead, the suspect part was carefully examined and coaxed back to life with the tools and materials on-hand.

While there’s plenty of folks who wouldn’t mind taking a few days off from lawn work while they wait for their replacement parts to arrive, not everyone can afford the luxury. Expedient repairs are critical when your livelihood depends on your equipment, which is why manufacturers making it harder and more expensive for farmers to fix their tractors has become such a major issue in right to repair battles all over the globe.

Repairing A Vintage HP 9825 The Hard Way

May 19, 2021 by Jonathan Bennett 16 Comments

[CuriousMarc] is at it again, this time trying to undo the damage from a poorly designed power circuit, that fried the internals of his HP 9825 computer. (Video, embedded below.)

The power supply on this particular model has a failure mode where a dying transistor can lead to 13 V on the 5 V line. This causes all the havoc one would expect on the internals of a 1970s era portable computer. This particular computer is rather rare, so instead of calling it a lost cause, our protagonist decides to replace the faulty transistor, install a proper overvoltage protection circuit, and then start the tedious hunt for which chips actually let their magic smoke out.
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