Repair Hacks

560 Articles

A picture of the bottom of the Pi 4 PCB, showing the three points you need to use to tap into the Pi 4 I2C bus going to the PMIC

Dead Raspberry Pi Boards, PMICs, And New Hope

March 24, 2023 by 22 Comments

Since the Raspberry Pi 3B+ release, the Pi boards we all know and love gained one more weakpoint – the PMIC chip, responsible for generating all the power rails a Pi needs. Specifically, the new PMIC was way more vulnerable to shorting 5V and 3.3V power rails together – something that’s trivial to do on a Raspberry Pi, and would leave you with a bricked board. Just replacing the PMIC chip, the MxL7704, wouldn’t help since the Raspberry Pi version of this chip is customized – but now, on Raspberry Pi forums, [Nefarious19] has reportedly managed to replace it and revive their Pi.

First off, you get a replacement PMIC and reflow it – and that’s where, to our knowledge, people have stopped so far. The next step proposed by [Nefarious19] is writing proper values into the I2C registers of the PMIC. For that, you’d want a currently-alive Pi – useful as both I2C controller for writing the values in, and as a source of known-good values. That said, if you go with the values that have been posted online, just having something like a Pi Pico for the I2C part ought to be enough.

[Nefarious19] reports a revived Pi, and this is way more hopeful than the “PMIC failures are unfixable” conclusion we’ve reached before. The instructions are not quite clear – someone else in the thread reports an unsuccessful attempt doing the same, and it might be that there’s a crucial step missing in making the values persist. However, such an advancement is notable, and we trust our readers to take the lead.

A week ago, [Mangy_Dog] on Hackaday Discord brought up fixing Raspberry Pi boards – given that the Raspberry Pi shortages are still an issue, digging up your broken Pi and repairing it starts making sense budget-wise. It’s no longer the ages where you could buy broken Pi boards by the hundred, and we imagine our readers have been getting creative. What are your experiences with fixing Raspberry Pi boards?

Fresh PCBs For The Quickshot II And II Plus Joysticks

March 21, 2023 by 13 Comments

The Quickshot II was released by Spectravideo in 1983 for the Commodore 64 and compatible systems, with the Quickshot II Plus following the next year. After decades of regular use, it’s quite understandable that these old-timers may be having some functional issues, but as long as the plastic parts are still good, [Stephan Eckweiler]’s replacement PCBs may be just the thing that these joysticks need to revitalize them for another few decades.

What may be a matter of taste is that these replace the nice tactile clicky switches on the QS II Plus with SMD push buttons, but compared to the stamped metal ‘button’ construction of the original QS II, the new board is probably a major improvement. As for the BOM, it features two ICs: a 74LS00 latch and NE555 timer, along with the expected stack of passives and switches, both through-hole and SMD.

The PCB contains break-off boards for the switches within the joystick itself, requiring a bit of wiring to be run to the main PCB before soldering on the DE-9 connector and connecting the joystick for a test run to a Commodore 64. All one needs now is a 3D printable enclosure version to create more QS II joysticks for some multiplayer action.

Replacing A Clock IC’s Battery

March 16, 2023 by 23 Comments

You can find a lot of strange things inside IC packages. For example, the Dallas DS12885 and DS12887 real time clock “chips” were available in a large package with an internal battery. The problem, of course, is that batteries die. [New Old Computer Show] wanted to restore a machine that used one of these devices and was able to repair the device. You can see two videos below. In the first video, he replaces both the battery and adds an external oscillator which would be necessary for the DS12885. However, he actually had the DS12887, which has an internal oscillator, something the second video explains.

The repair used a PCB he ordered from Tindie. However, the board is only part of the problem. You also need to disconnect the dead battery which requires a Dremel and a steady hand.

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Pi Picos Give Casio FX9000P Its Memory Back

March 8, 2023 by 12 Comments

Is the Casio FX9000P a calculator or a computer? It’s hard to tell since Casio did make calculators that would run BASIC. [Menadue] didn’t know either, but since it had a CRT, a Z80, and memory modules, we think computer is a better moniker.

He found one of these, but as you might expect, it needed a bit of work. There were two bad video RAM chips on the device, and [Menadue] used two Raspberry Pi Picos running a program to make them think they are RAM chips. The number of wires connecting the microcontollers might raise some eyebrows, but it does appear to get the job done.

He also used more Picos to emulate memory on cartridges. Then he used a test clip and a — you guessed it — another Pico to monitor the Z80 bus signals. It is amazing that the Pico can replace what would have been state-of-the-art memory chips and a very expensive logic analyzer.

The second video mostly shows the computer in operation. The use of Picos to stand in for so much is clever. It reminded us of the minimal Z80 computer that used an Arduino for support chips. The computer itself, though, reminded us more of a cheap version of the HP9845.

Continue reading “Pi Picos Give Casio FX9000P Its Memory Back” →

Showing a RAM chip being removed from a Pi 4 board, hot air gun in the shot. Area around the chip is covered with kapton tape.

Upgrade RAM On Your Pi 4, The Fun Way

March 5, 2023 by 17 Comments

The Raspberry Pi shortage has been a meme in hacker circles for what feels like an eternity now, and the Pi 4 seems to be most affected – though, maybe it’s just its popularity. Nevertheless, if you’re looking for a Pi 4, you would need to look far and wide – and things are way worse if you need the 8 GB version specifically. Or so we thought – [MadEDoctor] shows us that refreshing online store pages isn’t the only way, having successfully upgraded the RAM chip on the Pi 4 from 1 GB to 8 GB with help of a hot air gun.

These chips are BGA, and those might feel intimidating if you’re just starting out with hot air – however, we recommend you watch this video, as [MadEDoctor]’s approach is of the kind that brings BGA replacement to hobbyist level. First off, you get a compatible RAM chip somewhere like Aliexpress – lucky for us, those come equipped with a set of balls from the factory. The default balls are made of lead-free solder, and [MadEDoctor] reballed the RAM chip with leaded solder balls to lower the melting point, but it’s by no means a requirement that you do the same.

In fact, you only need a hot air gun, flux, a soldering iron and some solder wick to perform the replacement – no reballing equipment. Put some kapton or metal tape on the board for heat shielding, get the old chip off with hot air, use an iron with wick to clean the pads, add some flux, align the chip, then use hot air to solder a new chip onto the board. Replacing this chip can get your Pi 4 to the highly-sought-after 8 GB target – as an aside, we’re surprised that there was no configuration needed, as the Pi 4 booted right up and successfully recognized the extra RAM added.

We’d personally recommend preheating for such an upgrade – that said, this sure went without a hitch, and such a RAM swap method doesn’t require any stencils, solder paste or solder ball applications. Drop by the video description for compatible RAM chip part numbers, make sure you have your tacky flux and solder wick in order, and let [MadEDoctor] walk you through upgrading your Pi 4 the hacker way. Is this hack to your liking? Take it up a notch with this laptop soldered-in RAM upgrade journey, or that one RAM upgrade for an old GPU to comply to Apple’s whims.

A closeup of the faulty section of the dial - you can spot the plastic rivets that broke off

The Tale Of Two Broken Flukes

March 1, 2023 by 11 Comments

Some repairs happen as if by pure luck, and [Sebastian] shows us one such repair on Hackaday.io. He found two Fluke 175 meters being sold on eBay, with one having a mere beeper issue, and another having a “strange error”. Now, theoretically, swapping beepers around would give you one working meter and a kit of spare parts – but this is Fluke we’re talking about, and [Sebastian] wasn’t satisfied leaving it there.

First, he deduced that the beeper issue could be fixed by repositioning the piezo disk – and indeed, that brought the meter number one to working order. This left the mysterious error – the meter would only power up in certain rotations of the dial, and would misbehave, at that. Disassembly cleared things up – the dial mechanics failed, in that a half of the metal contacts came detached after all the plastic rivets holding the metal piece in place mysteriously vanished. The mechanics were indeed a bit intricate, and our hacker hoped to buy a replacement, but seeing the replacement switch prices in three-digit range, out came the epoxy tube.

An epoxy fix left overnight netted him two perfectly working Fluke meters, and while we don’t know what the listing price was for these, such a story might make you feel like taking your chances with a broken Fluke, too. The tale does end with a word of caution from [Sebastian], though – apparently, cleaning the meters took longer than the repairs themselves. Nevertheless, this kind of repair is a hobbyist’s dream – sometimes, you have to design a whole new case for your meter if as much as a wire breaks, or painstakingly replace a COB with a TQFP chip.

Fixing A Reflow Oven’s Conveyer Belt With An NE555 And Stepper Motors

February 23, 2023 by 10 Comments

Some design choices on manufacturing equipment really leave you scratching your head for a while, as recently happened to [Chris Cecil] when the belt on a reflow oven’s conveyer snapped. Although the solution seems simple enough, getting a new belt on the thing would involve essentially taking the entire machine apart, before reassembling it again. Thus the frayed belt went through the oven over and over until during a recent production run of Smoothieboard controller boards until [Chris] heard a funny noise and the conveyer ground to a halt.

Moving the conveyer by hand kind of worked, but with a more permanent fix urgently needed to finish the production run, two stepper motors took the place of the belt, which just left driving these steppers to keep the conveyer moving in sync. Lacking a simple Arduino board to toss at it, and with a Smoothieboard being absolute overkill, [Chris] figured that a humble NE555 timer IC ought to do the job just as well.

Using a project on Hackaday.io by [KushagraK7] as the starting point, and a 1992-vintage NE555 IC harvested from an old project, [Chris] managed to put together a basic stepper driver that uses the NE555 to provide the timing signal. In addition to restoring basic functionality like starting and stopping the conveyer belt, [Chris] added a new feature with the reversing of the conveyer direction. Along with some cobbled together components to physically rotate the conveyer’s two rollers, it restored the reflow oven to working condition.

And one day the prototyped driver board will be updated to a proper PCB. It’s only temporary, after all :)

Continue reading “Fixing A Reflow Oven’s Conveyer Belt With An NE555 And Stepper Motors” →