Hi Bill, Indeed, it seems bonkers. I assume it's because someone has a huge stash of open collector output 74 series shift registers, and either thinks they're the same, or that most people won't notice the difference.
I bought two batches of 500 of them, from two different chinese suppliers, and they are all exactly the same, having the same laser engraved batch number even. To be fair, the prices were suspiciously good, but I wasn't banking on fake shift register ICs.... They are badged as TI SN74HC595N, and batch GM1807FSF. I have some 'normal' SN74HC595N, and swapping these out for the real ones generates the expected behaviour ( and yes, inv G is indeed pulled low). With the 'fake' ones, they will appear to work OK with a pull up resistor present (as you'd expect with an open collector output), but are unable to source any current. I thought it was just me, but then I googled GM1807FSF and found someone else (in German) having the same problem! https://www.mikrocontroller.net/topic/463936 David On Fri, 25 Jan 2019 at 22:24, Bill van Dijk <[email protected]> wrote: > That is really weird. Please understand I am not questioning what you are > saying, but perhaps there is another explanation. The 74LS596 (I have never > seen an HC version) is indeed an open collector chip similar to the > 74HC595, which is a tri-state device. On the 74HC595 the inv G (pin 13) > should be held low for normal operation. If it goes high for any reason, > the output will float in tri-state mode, similar to what an open collector > would look like. As you say, I can’t for the life of me not figure why > anyone would bother to rebadge those chips especially since there does not > seem to be an economic one (which is usually the motivation). > > > > Bill > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *David Pye > *Sent:* Friday, January 25, 2019 4:12 PM > *To:* [email protected] > *Subject:* Re: [neonixie-l] Re: Counterfeit RTC modules > > > > It seems even things barely worth faking are being faked also. > > > > I have a bag of 500 74HC595 shift registers, that are actually rebadged > 74HC596s (as in, open collector, SINK, not SOURCE-capable). > > > > Which are useless for my application :-( > > > > > > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/008501d4b4fc%24bb636a80%24322a3f80%24%40gmail.com > <https://groups.google.com/d/msgid/neonixie-l/008501d4b4fc%24bb636a80%24322a3f80%24%40gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CAOQ6x0FggEjn0WWRt0MSRtvu9vkXDc2uN-VwEywE_85MLRa%3DiQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
