...and deliberately tombstoning an SMD resistor to install a mod wire to a production board is acceptable, too. From now on, whenever I do this I'll claim the board is hacked using the recommended industry standard technique. #electronics
...and the classic hack: stacking DIP chips on top of each other, lifting or cutting QFP pins for mod wires, are all accepted by IPC-7721 as legitimate methods for patching a production board. Interestingly, IPC-A-610 even allows stacked SMD resistors and capacitors by design, not limited to a modification.
Mod wires do have to follow some rules: secured by epoxy glue, not perpendicular to the pin, not crossing a component, and only a single wire should be used at a single pin. Also, zero-ohm resistors are acceptable pin bridges. #electronics
@niconiconi check out this amazing and terrifying thread https://twitter.com/GregDavill/status/1145001336213082113
@theruran Stacking DIP chips on top of each won't work for most systems. But it's a classic way to do a RAM/ROM mod in a 8/16-bit computer because these chips are special - all data and address pins have the same pinout and are connected together on the same tri-state bus to carry the same signals, so you can stack one on another. The only different signal is the Chip Select pin, you cut that pin and solder a jumper wire to the decoder logic you added so only one chip is selected at a time. tag #retrocomputing #electronics
@niconiconi you can get pre-stacked capacitors too, if you look for really high capacitance C0G ceramics
@niconiconi may I add, I'm also guilty of mounting smd resistors on their side. by design. pcb estate was tiGht :////
@JennyFluff It takes 10 second to fix a tombstoning resistor. The only reasonable use of this technique is when one resistor pad is connected to the wrong place due to a bug in the design and you need to patch that up (because you already made hundreds of boards).
@email@example.com i've seen an astounding number of bodges in avionics hardware i've looked at
@niconiconi I haven't seen this in this thread so I think this needs to be posted.
You can go even further with some bodges and claim they are according to NASA standards.
See https://workmanship.nasa.gov/lib/insp/2%20books/frameset.html, section 3.02 and 3.03
@ripper Thanks for posting. I know this NASA manual, but I didn't know it has an updated HTML version.
@niconiconi Yeah, I didn't know that too. I was searching for the PDF to link it, but found this instead.