22 Dec
2015
22 Dec
'15
1:10 p.m.
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-fix at xs4all.nl> escreveu:
-----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