Ask Hackaday: Calling All 68k Experts

This is a tale of old CPUs, intensive SMD rework, and things that should work but don’t.

Released in 1994, Apple’s Powerbook 500 series of laptop computers were the top of the line. They had built-in Ethernet, a trackpad instead of a trackball, stereo sound, and a full-size keyboard. This was one of the first laptops that looked like a modern laptop.

The CPU inside these laptops — save for the high-end Japan-only Powerbook 550c — was the 68LC040. The ‘LC‘ designation inside the part name says this CPU doesn’t have a floating point unit. A few months ago, [quarterturn] was looking for a project and decided replacing the CPU would be a valuable learning experience. He pulled the CPU card from the laptop, got out some ChipQuick, and reworked a 180-pin QFP package. This did not go well. The replacement CPU was sourced from China, and even though the number lasered onto the new CPU read 68040 and not 68LC040, this laptop was still without a floating point unit. Still, it’s an impressive display of rework ability, and generated a factlet for the marginalia of the history of consumer electronics.

Faced with a laptop that was effectively unchanged after an immense amount of very, very fine soldering, [quarterturn] had two choices. He could put the Powerbook back in the parts bin, or he could source a 68040 CPU with an FPU. He chose the latter. The new chip is a Freescale MC68040FE33A. Assured by an NXP support rep this CPU did in fact have a floating point unit, [quarterturn] checked the Mac’s System Information. No FPU was listed. He installed NetBSD. There was no FPU installed. This is weird, shouldn’t happen, and now [quarterturn] is at the limits of knowledge concerning the Powerbook 500 architecture. Thus, Ask Hackaday: why doesn’t this FPU work?

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Hackaday Links: March 20, 2016

Western Digital introduced their second revision of the PiDrive this week. This is a native USB hard drive – formatted to 314GB – based on the WD Blue drive. The earlier version of the WD PiDrive was 1TB, and cost about $70 USD. The new, 314GB version, sells for about $35. Does Western Digital manufacture 314GB hard drives? No, that would be stupid. Who’s taking bets on the actual capacity of these drives?

[SopaXorsTaker] has introduced us to a brand new way of removing BGA chips. PCBs are usually more flexible than chips, and a few whacks with a hammer is all that’s needed.

For the last few months, [quarterturn] has been upgrading a PowerBook 520. He’s trying to replace the CPU with a 68040 that has an FPU. His first attempt failed, and his second attempt – a new Freescale part that certainly has an FPU – also failed. It’s great experience in desoldering and reworking fine-pitch QFP parts, but [quarterturn] has no idea why the Apple System Profile reports an FPU-less CPU. It might be something in the ROM that tells the PowerBook not to use the FPU, in which case the obvious upgrade would be to replace the ROM with one from a PowerBook 550c or a Sonnet upgrade card. If you have either of those, I’m sure [quarterturn] would like to have a word with you.

LIDAR! We all know what the coolest use of LIDAR is, but it’s also useful for robots, drones, and other autonomous thingamadoos. Here’s a Kickstarter for a LIDAR module, 40 meter range, 360 degree range, 500 samples per second, and UART/USB connections.

[Bill] is trying to start a Makerspace in Fort Lauderdale. Here’s the indiegogo campaign.

We launched the 2016 Hackaday Prize this week. Why should you enter? Because last year, it seemed everyone who entered early won something. There’s $300,000 worth of prizes on the line. Need an idea? [Dave Darko] has just the thing for you. It’s the Hackaday Prize Buzzword Generator, the perfect thing for spitballing a few ideas and seeing what sticks.


Upgrading and Desoldering a Fake CPU

[quarterturn] had an old Apple Powerbook 520c sitting around in his junk bin. For the time, it was a great computer but in a more modern light, it could use an upgrade. It can’t run BSD, either: you need an FPU for that, and the 520 used the low-cost, FPU-less version of the 68040 as its main processor. You can buy versions of the 68040 with FPUs direct from China, which means turning this old Powerbook into a BSD powerhouse is just a matter of desoldering and upgrading the CPU. That’s exactly what [quarterturn] did, with an unexpected but not surprising setback.

The motherboard for the Powerbook 500 series was cleverly designed, with daughter cards for the CPU itself and RAM upgrades. After pulling the CPU daughter card from his laptop, [quarterturn] faced his nemesis: a 180-pin QFP 68LC040. Removing the CPU was handled relatively easily by liberal application of ChipQuik. A few quick hits with solder braid and some flux cleaned everything up, and the daughter card was ready for a new CPU.

The new FPU-equipped CPU arrived from China, and after some very careful inspection, soldering, and testing, [quarterturn] had a new CPU for his Powerbook. Once the Powerbook was back up and running, there was a slight problem. The chip was fake. Even though the new CPU was labeled as a 68040, it didn’t have an FPU. People will counterfeit anything, including processors from the early 90s. This means no FPU, no BSD, and [quarterturn] is effectively back to square one.

That doesn’t mean this exercise was a complete loss. [quarterturn] did learn a few things from this experience. You can, in fact, desolder a dense QFP with ChipQuik, and you can solder the same chip with a regular soldering iron. Networking across 20 years of the Macintosh operating system is a mess, and caveat emptor doesn’t translate into Mandarin.

Desoldering Doesn’t Necessarily Suck

What’s your favorite way to fix soldering mistakes or get usable components off that board you found in a Dumpster? I’ve always been partial to desoldering braid, though I’ve started to come around on the vacuum pump depending on the situation. [Proto G] sent in an Instructable that outlines nine different ways to desolder components that take varying amounts of time and skill.

He starts with one that is often overlooked if you don’t have a solder pot. [Proto G] recommends this method only when you don’t want to keep the board. Cover the solder joints of the components you want to keep with flux and hold it over the solder pot while pulling out the components with pliers. The flux isn’t critical, but it makes removal faster and easier.

For boards in need of repair, [Proto G] uses a manual pump or copper desoldering braid that comes coated with flux. If you can afford one, a desoldering machine seems like the way to go—it combines the heat of a soldering iron with the vacuum of a manual pump. Desoldering tweezers and hot air rework stations look like great ways to remove surface mount components.

If you enjoyed this, check out [Bil Herd’s] guide on component desoldering. There are also few ways that [Proto G] doesn’t mention, like holding the board over an alcohol flame. Let us know your favorite desoldering method in the comments.

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Tricky Repair of Power Driver for CNC Machine


Designing and building something from scratch is one thing. But repairing fried electronics is a much different type of dark art. This video from [Mike’s Electric Stuff] is from more than a year ago, but we didn’t think you’d mind since what he accomplishes in it is so impressive. He’s got a burnt out pick and place hybrid power module which isn’t going to fix itself.

The power module construction includes a part that has chip-on-board-style MOSFETs and the circuitry that goes with them enclosed in a black plastic housing. It’s kind of like a submodule was encapsulated using the same plastic as integrated circuits. After cracking it open it appears the bonding wire has burnt away. [Mike] connects a jumper wire to one of the board traces in order to use an external MOSFET. This is much easier said than done since the module substrate is ceramic designed to dissipate heat. We’re amused by his technique of melting the jumper into the plastic housing to protect it from the heat sink that goes over the package. In the end he gets his CNC running again. This may not be the best long-term fix but he just needed to continue running until a proper replacement part arrives.

Oh, one more thing: the Metcal vacuum desolderer he uses in the video… do want!

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Troubleshooting household light timers


When [Todd Harrison’s] Christmas lights stayed on well past the pre-defined shut off time, he knew there was something wrong with the timer. He took the device into his workshop and spent some time diagnosing and repairing the device, a process he recorded for all to see.

After busting the screw-less timer open with a hammer, he inspected the PCB for any apparent signs of damage. After seeing what looked like a damaged transistor, he desoldered it from the board for testing. After the transistor passed his tests with flying colors, [Todd] assumed that the fault had to be in the relay which the transistor was responsible for switching.

Sure enough, the relay had shorted out, and upon cutting it open he found that the contact points were fused together. He separated and sanded the contacts down, enabling him to get the timer working – at least for the time being.

Part of [Todd’s] goal with this video was to show off different methods of desoldering, including a manual solder sucker (my favorite), desoldering braid, and a purpose built desoldering iron. If you’re in the market for some desoldering tools, but don’t know what to buy, [Todd] is more than happy to offer his advice.

Continue reading to see a video of [Todd’s] troubleshooting process.

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Hackaday Links: April 13, 2011

Oven parts scrounging


In response to last week’s post about parts scrounging with a heat gun, Hackaday forum member [BiOzZ] decided to try doing the same thing in his oven. It seems to work quite well, but we’re wondering if there should be any concerns over the lead content of the solder. Anyone care to chime in?

Spill-proof parts holder


Have you ever been in the midst of disassembling something and knocked over your container full of screws onto the floor? [Infrared] has a simple solution to the problem which also happens to keep a couple of plastic bottles out of the landfill.

Easy button stops abuse of the word awesome


Do you often repeat a word ad nauseam? Make author Matt Richardson does, and he hacked a Staples “Easy” button to help him break his addiction to the word “Awesome”.

Cheap Remote-controlled baseboard lighting


[Sean] scored a pair of LED deck lighting kits for a steal and decided to install them into his newly renovated kitchen. They are currently remote operated, but he plans on adding an X10 interface as well as PIR sensors for automatic triggering in the near future.

Yet another LCD recapping guide


It starts with a finicky backlight, or perhaps a high-pitched whine from the back of your display – by now, we’re sure that everyone knows the symptoms of an LCD panel that’s just about to die. [Eric’s] Syncmaster recently quit on him, so he pried it open and got busy recapping. It’s running again, and he wanted to share his repair process in case others out there own the same display.