22 Dec
2015
22 Dec
'15
1:09 p.m.
-----Oorspronkelijk bericht-----
Van: cctalk [mailto:cctalk-bounces at classiccmp.org] Namens Terry Stewart
Verzonden: dinsdag 22 december 2015 21:50
Aan: General Discussion: On-Topic and Off-Topic Posts
Onderwerp: Piggybacking 74LS logic chips to confirm a suspected fault
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)
I use a HP 10529A logic comparator on regular basis for fault finding in ttl circuits.
It compares a reference chip with the CUT (Chip under test;) it's a very nice
diagnostic tool.
It's a bit like piggy backing just a little more sophisticated :0
-Rik