It used to be you could crack open a TV or radio and really work on the components inside. The smallest thing in there was maybe a disc capacitor a little smaller than your pinky’s nail. Nowadays, consumer electronic boards are full of tiny SMD components. Luckily [StezStix Fix?] has a microscope and the other tools you need. Someone sent him an Amazon Echo Show with a bad touchscreen. Can it be fixed?
The video below shows that it can, but there’s a twist. The bad capacitor was mounted on one of those flexible PCB cables that are so hard to work with. It is hard enough not to damage these when you aren’t trying to remove and replace a component from the surface of the cable.
There was a time when the desktop peripherals such as your keyboard and mouse were expensive items that you hung on to and cared for. But several decades of PC commoditization and ever-cheaper manufacturing have rendered each of them to an almost throwaway level, they are so cheap that when one breaks you can simply reach for another without thought.
This is not to say that there is no longer a space for a more costly specialist keyboard. You’ll find enthusiasts still clinging to their treasured vintage IBM Model Ms and Model Fs, or typing on a range of competing high end ‘boards. You might say that a cheap keyboard is pretty high quality these days, but for some people only the feel of a quality switch will do.
[Mac2612] was given a particularly nice example of this class of peripheral, a Das Keyboard 4C complete with trademark missing key decals. There was a snag though, it has suffered a spill at some time in its life, and would issue random keypresses which rendered it useless. His marathon investigation and repair of the fault makes for an interesting read, and gives us some insight into why these keyboards cost the extra money.
“To my dismay, I quickly realized that this was probably an unnecessary endeavor…”
At first it seemed as though corrosion on the board might be the issue, so he gave it a clean with IPA. All to no avail, and so began a succession of further dismantlings and cleanups which culminated in the desoldering of all the key switches. This lengthy task shows us in detail the construction of a high-end ‘board, but sadly it didn’t reveal the fault, and phantom keypresses kept appearing.
Following the board traces back to the microcontroller, he eventually found that moisture had corroded the end of a 10K surface mount resistor, leaving it with a resistance in the MOhms. Since it was a pulldown for one of the keyboard rows, he’d found the source of the problem. Having spent a long time fault-finding a board with an SMD part with a mechanical failure, we feel his pain.
Replacing the SMD parts and reassembly gave him a rather sweet keyboard, albeit for a lot of work.
