It works if the gate is open. But if it is shorted to gnd/vcc, you're in trouble :)
Enviado do meu Tele-Movel Em 22/12/2015 19:09, "Rik Bos" <hp-...@xs4all.nl> escreveu: > > > > -----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 > >
