Piggybacking 74LS logic chips to confirm a suspected fault

[Terry Stewart]

Hi,

I've written up my recent third Apple II repair, this time an Apple IIe.
http://www.classic-computers.org.nz/blog/2015-12-22-appleiIIe-no-video.htm

One interesting aspect of this repair is that piggy-backing a logic chip
helped confirm a faulty one. I'd only ever used this technique with RAM.
I'm sure it only works if the chip has a particular type of fault, but it
worked this time for me.

Terry (Tez)