Rohde & Schwarz FSIQ 7 Logic Analyzer's RF module, back side. (Source: Roberto Barrios)

Rohde & Schwarz FSIQ Signal Analyzer IF-Filter Module Repair

January 12, 2022 by Maya Posch 9 Comments

Who can’t resist snapping up a piece of really expensive laboratory testing gear for next to nothing when browsing eBay or similar? Maybe it’s giving you mournful eyes when browsing through a yard sale. Often such gear is sold for cheap because it’s defective, but with a bit of attention, can be brought back to life. This is how [Roberto Barrios] ended up with a Rohde & Schwarz FSIQ 7 signal analyzer lounging around his place for a few months until he got it fixed.

Part of the fix was replacing a busted RF converter module (A160 IF-Filter) with a used-but-working replacement, but this left the device with odd calibration failures. In the process of tracing down the cause, [Roberto] took many high-resolution images of both sides of the PCBs in order to reverse-engineer the circuit. To complicate matters, the calibration results indicated that the unit’s filters were fine on boot-up, but would deviate after a few minutes.

After extending the filter module to work outside the enclosure and experimental use of a hot air gun, ultimately the cause was tracked down to an unsoldered pad. Considering the extremely simple cause of the failure, it would seem that R&S QA had an off-day when that replacement module was produced. If there’s a lesson to be learned here it is probably that a simple visual inspection is sometimes all that is needed to fix a hardware issue.

What are your expensive gear repair stories? What did you learn that could save others hours of their time?

Get A Grip On Troubleshooting Your Vintage Pinball Machine

January 10, 2022 by Chris Wilkinson 1 Comment

Restoring vintage technology can be a tricky business, especially without the appropriate schematics and documentation. To this end [Mark] has spent the past twelve months building a comprehensive schematic editor and circuit simulator library for electromechanical pinball machines.

Rather than explore each and every table in excruciating detail, the emSim software aims to examine how specific circuits work, and how they are used as part of the gaming experience. The aim of the project is to aid in the diagnosis and repair of vintage electromechanical pinball machines, the types that rely on a dizzying array of switches, gears, motors and coils in their operation, operating like clockwork underneath the play field. While these older pinball machines typically use alternating current, the game logic (for the most part) is still binary, and can be effectively described with Boolean operators.

Like any machine with moving parts, these systems will eventually wear down and require servicing, a task which may not be in the wheelhouse for your casual pinball enthusiast. [Mark]’s hope is that his circuit simulations will allow just about anyone to repair these classic tables, and keep them around for future generations to explore and enjoy.

If tinkering with pinball innards isn’t for you, then make sure to check out our coverage of this awesome virtual pinball table.

Adding An Audio Jack To Classic Headphones Is A Nifty Upgrade

January 8, 2022 by Lewin Day 15 Comments

One of the most common ways to junk a pair of headphones is to damage the cord. Obviously, the lead can be repaired, but it involves busting out the soldering iron and can be tedious when dealing with the tiny little coated wires.

It does involve soldering, but ideally, you only have to do it once.

[mauriziomiscio.mm] has a way of dealing with the problem in a once-and-done fashion, by installing a female audio jack into his vintage headphones. The benefit is that if the cable is damaged, it can simply be unplugged and replaced with a new one, and is commonly seen on headphones from companies like KRK.

The hack is simple when applied to a classic pair of AKG K141 headphones. The little plastic casing on one earpiece is popped off, and replaced with a 3D-printed version that stoutly holds a female TRS jack in place. This can then be soldered up to the wiring inside the headphones.

With everything assembled, the headphones can now use an easily-replaceable cable, and one needn’t worry about having to bust out the soldering iron if the lead is damaged in future. It’s a particularly useful hack for those who use their headphones on the road, always throwing them into backpacks between gigs.

If that’s not hardcore enough, consider attaching a headphone jack to an old 8-track player for the most ridiculous Walkman you can imagine. If you’ve been working on your own portable audio hacks, be sure to drop us a line!

An image describing parts of a Tesla modem board

LTE Modem Transplant For A Tesla Imported Into Europe

January 3, 2022 by Arya Voronova 24 Comments

When modern connected cars cross continents, novel compatibility problems crop up. [Oleg Kutkov], being an experienced engineer, didn’t fret when an USA-tailored LTE modem worked poorly on his Tesla fresh off its USA-Europe import journey, and walks us through his journey of replacing the modem with another Tesla modem module that’s compatible with European LTE bands.

[Oleg]’s post goes through different parts on the board and shows you how they’re needed in the bigger picture of the Tesla’s Media Computer Unit (MCU), even removing the LTE modem’s shield to describe the ICs underneath it, iFixit teardown diagram style! A notable highlight would be an SIM-on-chip, essentially, a SIM card in an oh-so-popular DFN package, and thankfully, replacing it with a socket for a regular SIM card on some extender wires has proven fruitful. The resulting Tesla can now enjoy Internet connectivity at speeds beyond those provided by EDGE. The write-up should be a great guide for others Tesla owners facing the same problem, but it also helps us make electric cars be less alike black boxes in our collective awareness.

Not all consequences of Tesla design decisions are this minor; for instance, this year, we’ve described a popular eMMC failure mode of Tesla cars and how Tesla failed to address it. Thankfully, Tesla cars are becoming more of a hacker community target, whether it’s building a computer-vision-assisted robot to plug in a charging cable, getting it repaired for a fraction of the dealership cost, or even assembling your own Tesla from salvage parts!

A CH341 programmer dongle with a stack of adapters on top (one for 1.8V and one for clip connection), and a test clip to the right of it

BIOS Flashing Journey Writeup Puts Tutorials To Shame

December 26, 2021 by Arya Voronova 18 Comments

A couple of weeks ago, [Doug Brown] bought a Ryzen motherboard, advertised as “non-working” and discounted accordingly. He noticed that the seller didn’t test it with any CPUs old enough to be supported by the board’s stock BIOS revision, and decided to take a gamble with upgrading it.

Not having a supported CPU in hand either, he decided to go the “external programmer” route, which succeeded and gave this board a new life. This is not why we’re writing this up, however. The reason this article caught our eye is because [Doug]’s research leaves no stone unturned, and it’s all there to learn from. Whether through careful observation or thorough research, this article covers all the important points and more, serving as an example to follow for anyone looking to program their BIOS.

For instance, [Doug] correctly points out a design issue with these common programmers resulting in 5 V getting onto the 3.3 V data lines, and fixes it by rewiring the board. Going through all the letters in the ICs part number, something that many of us would dismiss, [Doug] notices that the flash chip is 1.8 V-only and procures a 1.8 V adapter to avoid the possibility of frying his motherboard. After finding out that the 1.8 V adapters don’t work for some people, he reverse-engineers the adapter’s schematics and confirms that it, indeed, ought to work with the specific parts on adapter he received.

Noting another letter in the part number implying the flash chip might be configured for quad-SPI operation, he adds series resistors to make sure there’s no chance of the programmer damaging the BIOS chip with its hardwired pinout. This is just an example of the insights in [Doug]’s article, there’s way more that we can’t mention for brevity, and we encourage you to check it out for yourself.

With this level of care put into the process, it’s no surprise that the modification was successful. The kind of inquisitiveness shared here is worth aspiring to, and writeups like this often surpass general-purpose tutorials in their insights and usefulness. What’s your “successfully making use of something sold as non-working” story?

If you’re looking for other insightful BIOS stories, we’ve covered someone reverse-engineering their BIOS to remove miniPCIe card whitelisting. We’ve typically covered BIOS modification stories in laptops, since there’s more incentives to modify these, but a lot of laptop BIOS articles will apply to desktop motherboards too, such as this supervisor password removal story or this LibreBoot installation journey by our own [Tom Nardi].

Thank you [Sidney] for sharing this with us!

A briefcase sized electronic machine with many indicator lamps and switches

Restoring A Vintage IBM I/O Tester

December 19, 2021 by Chris Wilkinson 12 Comments

By now, [CuriousMarc] and his team of volunteers are well versed in 1960s hardware restoration. So when a vintage IBM I/O Tester came into their possession, a full machine makeover was all but inevitable.

The I/O Tester dates from around 1965, which roughly coincides with the introduction of IBM’s lauded System/360 computer mainframe. In addition to the computer itself, business customers could order a variety of peripherals with their computing system. These included storage devices, printers, additional operator consoles, and so on. Since these peripherals shared the same I/O design, a portable hardware testing rig was a sensible design choice. One portable low-voltage tester could be paired with any number of IBM peripherals, doing away with the need to have unique debugging panels on every piece of computing hardware.

Fast forward to the present day, and the IBM I/O Tester looks positively antique with its blinkenlight lamp panel and switches. To use the tester, simply connect up one (or both) of its chunky 104-pin connectors to your IBM peripheral of choice, insert the accompanying paper overlay, and voilà. Operators could then observe the status of the many lamps to evaluate the inner digital workings of the connected peripheral. Depending on the connected hardware, the tester could reveal the contents of data registers, printing status, disk and tape transfer status, and probably much more. The purpose of the tester’s ninety indicator lights is completely dependent on the attached peripheral, and the paired paper overlays are essential to comprehend their meaning.

After [Ken Shirriff] deciphered the documentation, it wasn’t long before the tester could be powered up using 24 VAC (normally supplied by the equipment being tested). Several burned out lamps were noted for replacement. The lamp assemblies required minor surgery due to a dubious design choice, and at least one of the toggle switches needed a new guide and a heavy dose of contact cleaner before it came back to life.

For the moment, [CuriousMarc] is using the blinkenlights panel as a surprisingly striking retro clock. With a literal truckload of vintage IBM hardware sitting in his storage, it’ll be exciting to see whether this restored tester will be pulled back into operational service someday. Readers should also check out our coverage of his previous major project, restoring an Apollo Guidance Computer.

Continue reading “Restoring A Vintage IBM I/O Tester” →

PCB Microsurgery Puts The Bodges Inside The Board

December 14, 2021 by Dan Maloney 23 Comments

We all make mistakes, and there’s no shame in having to bodge a printed circuit board to fix a mistake. Most of us are content with cutting a trace or two with an Xacto or adding a bit of jumper wire to make the circuit work. Very few of us, however, will decide to literally do our bodges inside the PCB itself.

The story is that [Andrew Zonenberg] was asked to pitch in debugging some incredibly small PCBs for a prototype dev board that plugs directly into a USB jack. The six-layer boards are very dense, with a forest of blind vias. The Twitter thread details the debugging process, which ended up finding a blind via on layer two shorted to a power rail, and another via shorted to ground. It also has some beautiful shots of [Andrew]’s “mechanical tomography” method of visualizing layers by slowly grinding down the surface of the board.

[Andrew] has only tackled one of the bodges at the time of writing, but it has to be seen to be believed. It started with milling away the PCB to get access to the blind via using a ridiculously small end mill. The cavity [Andrew] milled ended up being only about 480 μm by 600 μm and only went partially through a 0.8-mm thick board, but it was enough to resolve the internal short and add an internal bodge to fix a trace that was damaged during milling. The cavity was then filled up with epoxy resin to stabilize the repair.

This kind of debugging and repair skill just boggles the mind. It reminds us a bit of these internal chip-soldering repairs, but taken to another level entirely. We can’t wait to see what the second repair looks like, and whether the prototype for this dev board can be salvaged.

Thanks to [esclear] for the heads up on this one.