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0 pointssolardev3y ago0 comments

I spilled water on my favorite keyboard and broke it, then let it dry and fixed it by using a pencil to trace over the damaged circuits. It worked fine again after that!

(Graphite in pencil lead is a weak conductor, enough to make the keyboard circuit work)

0 comments

jonah-archive3y ago

That phenomenon is the source of one of my all-time favorite man page entries: https://web.archive.org/web/20210421224904/https://nixdoc.ne...

     ep0: 3c509 in test mode. Erase pencil mark!  This means that someone has
     scribbled with pencil in the test area on the card.  Erase the pencil
     mark and reboot.  (This is not a joke).

It's the E1 pad between the barcode and the empty BIOS socket: https://en.wikipedia.org/wiki/3Com_3c509#/media/File:3Com_3C...

drewzero13y ago

That's awesome! I have a handful of those 3Com cards kicking around at work. Will definitely have to check that out.

solardevOP3y ago

Hah, that's really great! Does that mean they used that to switch it into a test mode during development?

jonah-archive3y ago

Pretty much -- IIRC connecting the pad bypasses the internal EEPROM and loads a default configuration, and from there you can read/write the EEPROM as well.

1 more reply

lagrange773y ago

I like it, because you used your knowledge to minimally invasively fix the problem.

emmelaich3y ago

You can use the same trick to repair 'broken' TVs and monitors; ones that just mysteriously stop displaying but are otherwise ok.

ecef9-8c0f-43743y ago

that's what I call a hack

j / k navigate · click thread line to collapse

0 comments

jonah-archive3y ago

That phenomenon is the source of one of my all-time favorite man page entries: https://web.archive.org/web/20210421224904/https://nixdoc.ne...

     ep0: 3c509 in test mode. Erase pencil mark!  This means that someone has
     scribbled with pencil in the test area on the card.  Erase the pencil
     mark and reboot.  (This is not a joke).

It's the E1 pad between the barcode and the empty BIOS socket: https://en.wikipedia.org/wiki/3Com_3c509#/media/File:3Com_3C...

drewzero13y ago

That's awesome! I have a handful of those 3Com cards kicking around at work. Will definitely have to check that out.

solardevOP3y ago

Hah, that's really great! Does that mean they used that to switch it into a test mode during development?

jonah-archive3y ago

Pretty much -- IIRC connecting the pad bypasses the internal EEPROM and loads a default configuration, and from there you can read/write the EEPROM as well.

1 more reply

lagrange773y ago

I like it, because you used your knowledge to minimally invasively fix the problem.

emmelaich3y ago

You can use the same trick to repair 'broken' TVs and monitors; ones that just mysteriously stop displaying but are otherwise ok.

ecef9-8c0f-43743y ago

that's what I call a hack

j / k navigate · click thread line to collapse