> -----Oorspronkelijk bericht----- > Van: cctalk [mailto:cctalk-boun...@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