Fixing An Agilent Oscilloscope Power Supply

April 18, 2020 by Jenny List 22 Comments

We should all be so lucky as [Salvaged circuitry], who scored a cheap Agilent oscilloscope from an online auction. Of course, its low price had a reason behind it, the ‘scope didn’t work. At fault was its power supply, the repair of which was documented in the video below.

These ‘scopes have relatively straightforward 12 V power supplies, extremely similar to off-the-shelf parts. The video is an interesting primer in switch-mode power supply repair, as the obvious failure of the filter capacitor and a MOSFET is traced further to the PSU controller chip. We see a new capacitor mounted proud of the board to reduce the risk of heat damage, and then some careful solder rework to save some lifted pads.

The result, a working oscilloscope. Maybe we’d have hacked in another 12 V supply, but given that this is a piece of test equipment perhaps it’s best to stay as close to the original spec as possible. As a parting shot he shows us an equivalent power supply, and promises us a side-by-side test in a future video.

These ‘scopes aren’t as popular in our circles as the cheaper Rigol range, but it’s worth remembering that they also have a budget model.

Continue reading “Fixing An Agilent Oscilloscope Power Supply” →

3.2 GHz Vector Signal Generator Tear Down

March 17, 2020 by Al Williams 15 Comments

[The Signal Path] snagged a fancy Rohde & Schwarz vector signal generator that can go up to 3.2 GHz, but sadly it wasn’t in working order. It powered up and even put out a 1 GHz signal, but the amplitude output was very wrong. Interestingly relative changes to the output were correct, it was just that the absolute output amplitude was off by quite a bit and changed with frequency. That started a detective job which you can follow along in the video below.

The instrument is pretty high-end, and did not report any problems even during self-check. This implied that all the internals were probably good and whatever was wrong probably lay close to the output. The service manual’s block diagram wasn’t terribly useful, especially given that all the processing portions appear to work well.

Continue reading “3.2 GHz Vector Signal Generator Tear Down” →

Dissecting China-Sourced Vintage HP 1970s ICs: Genuine Or Not?

March 16, 2020 by Maya Posch 10 Comments

While repairing a real-time clock module for a 1970s HP computer that had been damaged by its leaky internal battery, [CuriousMarc] began to suspect that maybe the replacement clock chips which he had sourced from a seller in China were the reason why the module still wasn’t working after the repairs. This led him down the only obvious path: to decap and inspect both the failed original Ti chip and the replacement chip.

The IC in question is the Texas Instruments AC5948N (along with the AC5954N on other boards), which originally saw use in LED watches in the 1970s. HP used this IC in its RTC module, despite it never having been sold publicly. This makes it even more remarkable that a Chinese seller had the parts in stock. As some comments on the YouTube video mention, back then there wasn’t as much secrecy around designs, and it’s possible someone walked out of the factory with one of the masks for this chip.

Whether true or not, as the video (also included after the break) shows, both the original 1970s chip and the China-sourced one look identical. Are they original stock, or later produced from masks that made their way to Asia? We’ll probably never know for sure, but it does provide an exciting opportunity for folk who try to repair vintage equipment.

Continue reading “Dissecting China-Sourced Vintage HP 1970s ICs: Genuine Or Not?” →

Plastic Cleanup Via Retrobrighting

March 13, 2020 by Al Williams 31 Comments

If you work on old radios, electronics is only one of the skills you need. The other is wood or metal working to restore the cabinets and chassis. However, more recent electronics have plastic and old plastic tends to turn yellow. [Odd Experiments] shows how to whiten plastic using a UV light source, aluminum foil, and hydrogen peroxide. Generally, ABS is the plastic at fault, especially those mixed with bromine as a fire retardant. You can see the results in the video below.

Note the peroxide in use was 12% — much stronger than what’s probably in your medicine cabinet. That’s usually only 3% solution, although you can get different strengths including some over 30% if you shop. However, if you search you’ll find that people have used 12%, 6%, and even 3% successfully, although we’d imagine it takes more time with 3%.

Continue reading “Plastic Cleanup Via Retrobrighting” →

See The Damage 250-Pound Combat Robots Get

March 9, 2020 by Donald Papp 14 Comments

Combat robots have been a thing for a while, but we don’t normally get a close look at the end results of the sort of damage they can both take and deal out. [Raymond Ma] spent time helping out with season four of BattleBots and wrote about the experience, as well as showed several pictures of the kind of damage 250-pound robots can inflict upon each other. We’ve embedded a few of them here, but we encourage you to read [Raymond]’s writeup and see the rest for yourself.

The filming for a season of BattleBots is done in a relatively short amount of time, which means the pacing and repair work tends to be more fast and furious than slow and thoughtful. [Raymond] says that it isn’t uncommon for bots, near the end of filming, to be held together with last-minute welds, wrong-sized parts, and sets of firmly-crossed fingers. This isn’t because the bots themselves are poorly designed or made; it’s because they can get absolutely wrecked by the forces at play.

Continue reading “See The Damage 250-Pound Combat Robots Get” →

Dumpster Finds Combined Into 4K Desktop Monitor

March 6, 2020 by Tom Nardi 31 Comments

Dumpster diving is a time honored tradition in the hacking community. You can find all sorts of interesting hardware in the trash, and sometimes it’s even fully functional. But even the broken gadgets are worth taking back to your lair to strip for parts. If you’re as lucky as [Jamz], you might be able to mash a few devices together and turn them into something usable.

In this case, [Jamz] scored a LG 27UK650 monitor with a cracked display and a Dell OptiPlex 7440 “All-in-One” computer that was DOA. Separately these two pieces of gear were little more than a pile of spare parts waiting to be liberated. But if the control board could be salvaged from the monitor, and the working LCD pulled from the Dell…

After taking everything apart, [Jamz] made a frame for this new Frankenstein monitor using pieces of aluminum channel from the hardware store and 3D printed side panels. With the Dell LCD mounted in the skeletal frame, the control board from the LG monitor was bolted to the back and wired in. Finally the center section of the LG monitor’s back panel was cut out and mounted to the new hybrid display with a 3D printed frame.

Admittedly, these were some pretty solid finds as far as trash goes. You won’t always be so lucky. But if you can keep an open mind, the curb is littered with possibilities. How about some impressive home lighting that started life as a cracked flat screen TV?

The Art Of USB Dongle Repair

February 20, 2020 by Erin Pinheiro 40 Comments

Faced with a broken USB dongle for our wireless devices, most of us would likely bin the part and order a replacement, after all the diminutive size of those things probably means hard to impossible repairability, right? Well, [The Equalizor] took it as a challenge and used the opportunity to practice his microscopic soldering skills just for funsies.

The wireless adapter in question, which came from one of his clients who accidentally bent it while it was plugged into a laptop, refused to be recognized by a computer under any circumstances. After sliding out the metal casing for the USB plug and snapping off the plastic housing, [The Equalizor] discovered that the slightly bent exterior hid a deeply cracked PCB. Then, with an inspection of the severed traces and lifted components, it was simply a matter of reflowing solder a few times to try to make the board whole again. Once the dongle was confirmed working, a new 3D shell was printed for it, replacing the original which had to be broken off.

It might not seem extraordinary to some people, but this video is a good example to show that repairs to delicate electronics in such a small scale are feasible, and can serve to reduce the amount of electronic waste we constantly dump out. Just because some electronics seem dauntingly elaborate or beyond salvaging, it doesn’t always mean there isn’t light at the end of the tunnel. You can see the work performed on this tiny dongle after the break.

Continue reading “The Art Of USB Dongle Repair” →