Piggybacking 74LS logic chips to confirm a suspected fault

Terry Stewart terry at webweavers.co.nz
Tue Dec 22 14:50:01 CST 2015


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)


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