Board worked perfectly for four months. Swapped all 68 switches for linears, and now the entire bottom row registers nothing, spacebar included. Everything else is fine. One switch had a slightly bent pin which I straightened before inserting, and I did notice a bit more resistance on one of the bottom row sockets. No visible damage from the top, no bent pins now.
For next time: hotswap sockets are held on by solder pads about the size of a grain of rice and they hate lateral force. Always check the pins are dead straight against something flat, always press straight down, and always support the back of the PCB with your other hand or lay it on a hard surface. Five pin switches with the plastic legs need to line up perfectly or they lever the socket sideways as they go in.
Clipping the two plastic legs off five pin switches is also completely fine if the plate holds them. Saves a lot of grief on hotswap boards.
Quick way to tell where to look in general: a dead row points at a row trace or its diodes, a dead column points at the controller pin or the column trace, and scattered dead keys point at switches. Also worth flashing the stock firmware again and checking the matrix definition, because if you touched the keymap at any point you can produce exactly this symptom in software.
Before the iron comes out, try the board with a different cable and port. Rare, but partial power delivery has faked a dead row for me once.
@node_red_ned · 8mo ago · 3 replies
A whole row failing at once is a matrix fault, not twelve simultaneous switch faults. The switches are almost certainly fine.
In a keyboard matrix, every key in a row shares one trace and usually a set of diodes. If one point in that line breaks, everything downstream of it goes quiet. Your bent pin story fits: the extra resistance you felt was the pin catching the socket, and the socket has almost certainly lifted its pad off the PCB, breaking the trace for the whole row.
To confirm, take all the bottom row switches out, open a text editor, and short each socket by bridging its two contacts with tweezers. If nothing types anywhere in the row, it is the board. If one particular socket also looks slightly raised or tilted compared with its neighbours, that is your culprit.
Fix is usually a reflow of that socket, and if the pad has actually torn off, a short bodge wire from the socket leg to the next point on the trace. Neither is hard, but you need an iron.
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@blown_cap · 8mo ago
Good chance you can see it under a phone camera zoomed in. A lifted socket sits a fraction of a millimetre proud and the solder fillet looks cracked and grey rather than shiny.
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@crypt_cass · 8mo ago
Tweezer test confirms nothing in the row responds. One socket on the bottom left is visibly tilted. Time to borrow an iron.
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