"Retro Repair" key electronics skills?

Mouse mouse at Rodents-Montreal.ORG
Tue May 10 09:16:53 CDT 2016

> - Since I'm a coder, I understand boolean logic (which I hope would
> help with ICs).

While it's an understandable point of view, especially for a coder, not
all ICs are digital logic - and even for those that are, understanding
non-digital-logic aspects of them can be useful.  (I built an EPROM
reader out of SSI TTL, and found it always read the last octet as FF
even in cases where I knew better.  Turned out I forgot to connect the
ground pin on the EPROM to circuit power ground; provided at least one
input was low, it powered the chip through the input protection diodes,
but when all connected pins were high - and all the non-address inputs
that weren't high were tied to the ground pin - then all outputs
perforce were too.  But that failure mode would have been inexplicable
if my mental model of the thing had been an ideal logic device.)

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