Repairdown: Disklavier DKC500RW Control Unit

If you’ve been kind enough to accompany me on these regular hardware explorations, you’ve likely recognized a trend with regards to the gadgets that go under the knife. Generally speaking, the devices I take apart for your viewing pleasure come to us from the clearance rack of a big box retailer, the thrift store, or the always generous “AS-IS” section on eBay. There’s something of a cost-benefit analysis performed each time I pick up a piece of gear for dissection, and it probably won’t surprise you to find that the least expensive doggy in the window is usually the one that secures its fifteen minutes of Internet fame.

DKC500RW installed on right side.

But this month I present to you, Good Reader, something a bit different. This time I’m not taking something apart just for the simple joy of seeing PCB laid bare. I’ve been given the task of repairing an expensive piece of antiquated oddball equipment because, quite frankly, nobody else wanted to do it. If we happen to find ourselves learning about its inner workings in the process, that’s just the cost of doing business with a Hackaday writer.

The situation as explained to me is that in the late 1990’s, my brother’s employer purchased a Yamaha Mark II XG “Baby Grand” piano for somewhere in the neighborhood of $20,000. This particular model was selected for its ability to play MIDI files from 3.5 inch floppy disks, complete with the rather ghostly effect of the keys moving by themselves. The idea was that you could set this piano up in your lobby with a floppy full of Barry Manilow’s greatest hits, and your establishment would instantly be dripping with automated class.

Unfortunately, about a month or so back, the piano’s Disklavier DKC500RW control unit stopped reading disks. The piano itself still worked, but now required a human to do the playing. Calls were made, but as you might expect, most repair centers politely declined around the time they heard the word “floppy” and anyone who stayed on the line quoted a price that simply wasn’t economical.

Before they resorted to hiring a pianist, perhaps a rare example of a human taking a robot’s job, my brother asked if he could remove the control unit and see if I could make any sense of it. So with that, let’s dig into this vintage piece of musical equipment and see what a five figure price tag got you at the turn of the millennium.

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Reproducing Vintage Plastic Parts In Top-Notch Quality

Plastic is a highly useful material, but one that can also be a pain as it ages. Owners of vintage equipment the world over are suffering, as knobs break off, bezels get cracked and parts warp, discolor and fail. Oftentimes, the strategy has been to rob good parts from other broken hardware and cross your fingers that the supply doesn’t dry up. [Eric Strebel] shows us that’s not the only solution – you can replicate vintage plastic parts yourself, with the right tools.

In the recording industry there’s simply no substitute for vintage gear, so a cottage industry has formed around keeping old hardware going. [Eric] was tasked with reproducing VU meter bezels for a classic Neve audio console, as replacement parts haven’t been produced since the 1970s.

The first step is to secure a good quality master for replication. An original bezel is removed, and polished up to remove scratches and blemishes from 40+ years of wear and tear. A silicone mold is then created in a plywood box. Lasercut parts are used to create the base, runner, and vents quickly and easily. The mold is then filled with resin to produce the final part. [Eric] demonstrates the whole process, using a clear silicone and dyed resin to make it more visible for the viewer.

Initial results were unfortunately poor, due to the silicone and hardener used. The parts were usable dimensionally, but had a hazy surface finish giving very poor optical qualities. This was rectified by returning to a known-good silicone compound, which was able to produce perfectly clear parts first time. Impressively, the only finishing required is to snap off the runner and vents. The part is then ready for installation. As a final piece of showmanship, [Eric] then ships the parts in a custom laser-engraved cardboard case. As they say, presentation is everything.

With modern equipment, reproducing vintage parts like knobs and emblems is easier than ever. Video after the break.

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Recover Data From Damaged Chips

Not every computer is a performance gaming rig. Some of us need cheap laptops and tablets for simple Internet browsing or word processing, and we don’t need to shell out thousands of dollars just for that. With a cheaper price tag comes cheaper hardware, though, such as the eMMC standard which allows flash memory to be used in a more cost-advantageous way than SSDs. For a look at some the finer points of eMMC chips, we’ll turn to [Jason]’s latest project.

[Jason] had a few damaged eMMC storage chips and wanted to try to repair them. The most common failure mode for his chips is “cratering” which is a type of damage to the solder that holds them to their PCBs. With so many pins in such a small area, and with small pins themselves, often traditional soldering methods won’t work. The method that [Jason] found which works the best is using 0.15 mm thick glass strips to aid in the reflow process and get the solder to stick back to the chip again.

Doing work like this can get frustrating due to the small sizes involved and the amount of heat needed to get the solder to behave properly. For example, upgrading the memory chip in an iPhone took an expert solderer numerous tries with practice hardware to finally get enough courage to attempt this soldering on his own phone. With enough practice, the right tools, and a steady hand, though, these types of projects are definitely within reach.

[Leo] Repairs A MIDI Sequencer

We all have that friend who brings us their sad busted electronics. In [Leo’s] case, he had a MIDI sequencer from a musician friend. It had a dead display and the manufacturer advised that a driver IC was probably bad, even sending a replacement surface mount part.

[Leo] wasn’t convinced though. He knew that people were always pushing on the switches that were mounted on the board and he speculated that it might just be a bad solder joint. As you can see in the video below, that didn’t prove out.

The next step was to fire up a hot air gun. Instead of removing the chip, he wanted to reflow the solder anyway. He was a little worried about melting the 7-segment LEDs so he built a little foil shield to protect it. That didn’t get things working, either.

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The Mystery Of The Clacking Clanking Scraping Sound

Hackers tend to face household problems a little differently than ordinary folk. Where the average person sees a painful repair bill or a replacement appliance, the hacker sees a difficult troubleshooting job and the opportunity to save some cash. [trochilidae] was woken one day by the dreaded Clacking Clanking Scraping Sound, or CCSS, and knew that something had to be done.

[trochilidae] reports that usually, the CCSS is due to the child of the house destroying his lodgings, but in this case, the source was laundry based. The Miele tumble dryer was acting up, and in need of some attention. What follows is a troubleshooting process [AvE] would be proud of – careful disassembly to investigate the source of the problem. Initial efforts found a loose bulb that was unrelated, before landing on a mysterious spring that wouldn’t fit back into place. In the end, that’s because it had no right to be there at all – an underwire had escaped from a bra, before becoming entangled in the dryer’s bearing.¬†With the culprit identified and removed, it was a simple reassembly job with some attention also paid to the condenser and filters to keep things in ship-shape.

It just goes to show – a bad noise, if properly investigated in a prompt manner, doesn’t have to be the end of the world. A bit of investigation goes a long way, and can save you a lot of money and heartache.

We’ve seen appliances giving hackers trouble before – like this aging washing machine that got its mechanical brain replaced with an Arduino.

A Daring Search For Answers In Soyuz Mystery

If you happened to tune into NASA TV on December 11th, you’d have been treated to a sight perhaps best described as “unprecedented”: Russian cosmonauts roughly cutting away the thermal insulation of a docked Soyuz spacecraft with a knife and makeshift pair of shears. Working in a cloud of material ripped loose during the highly unusual procedure,¬†cosmonauts Oleg Kononenko and Sergey Prokopyev were effectively carving out their own unique place in space history. Their mission was to investigate the external side of the suspicious hole in the Soyuz MS-09 capsule which caused a loss of air pressure on the International Space Station earlier in the year.

That astronauts don’t generally climb out the hatch and use a knife to hack away at the outside of their spacecraft probably goes without saying. Such an event has never happened before, and while nobody can predict the future, odds are it’s not something we’re likely to see again. Keep in mind that this wasn’t some test capsule or a derelict, but a vehicle slated to return three human occupants to Earth in a matter of days. Cutting open a spacecraft in which human lives will shortly be entrusted is not a risk taken likely, and shows how truly desperate the Russian space agency Roscosmos is to find out just who or what put a hole in the side of one of their spacecraft.

Close inspection from the inside of the spacecraft confirmed the hole wasn’t made by an impact with a micrometeorite or tiny piece of space junk as was originally assumed. It appears to have been made with a drill, which really only allows for two possible scenarios: intentional sabotage or a mistake and subsequent cover-up. In either event, a truly heinous crime has been committed and those responsible must be found. As luck would have it the slow leak of air pressure was detected early and the hole was patched before any damage was done, but what if it hadn’t?

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Vintage IBM 1403 Printer Problem Evades An Easy Fix

The Computer History Museum in Mountain View has two operational IBM 1401 mainframes, which use IBM 1403 high-speed printers. They aren’t some decades-old notion of “high speed” that barely looks sluggish today, either. These monsters slam out ten lines per second thanks to a rotating chain of type slugs and an array of electromagnetic hammers. Every 11.1 microseconds, a character in the chain would be lined up with a hammer, and if the control circuitry identified it as a character that needed to be printed, the hammer behind the paper would drive the paper into the print ribbon and the slug, putting an imprint of the character onto the paper. When one of these printers failed with a sync error, it kicked off some serious troubleshooting to diagnose the problem.

The IBM 1403’s type chain has a repeating set of characters that spins around at high speed. Unlike a typewriter or label maker, the hammers are not inside this unit. The hammers are on the outside, and work by pressing the paper onto the type slugs as the required characters line up.

Investigation of the problem ultimately led to an intermittent connection in a driver card due to a broken PCB trace, but by then some fuses had been blown as well. In the end the printer was brought back online, but possibly with a slightly damaged coil on one of the hammers.

[Ken]’s writeup on the repair process is highly detailed and walks through the kind of troubleshooting and repairs involved when solving problems with vintage electronics. Electrical fundamentals might be the same, but a deep understanding of not only the architecture but also the failure modes of vintage hardware is needed in order to troubleshoot effectively.

If IBM 1401 mainframes and fixing 1403 printers sounds familiar, it’s because a printer fix has been done before. That was due to a different problem, but still a challenging task to narrow down and fix.