I tried those suggestions and nothing changed, there's around 4ma total through the LEDs now so it shouldn't be in meltdown mode.
On Tuesday, 26 September 2023 at 17:45:06 UTC+1 Craig Garnett wrote: > Thanks, > I'll give those suggestions a go. > > On Tuesday, 26 September 2023 at 16:05:17 UTC+1 gregebert wrote: > >> 74xx TTL devices have a rather high input-low current, on the order of >> 1mA, so you should use a much smaller pulldown resistor, say 100 ohms, or >> perhaps none at all. Logically, it should not be possible for more than 1 >> output to get driven low on the 7441, but that only applies if all >> parameters in the datasheet are met. I suspect that the 100K pulldown isn't >> really pulling-down to a logic-zero, and the IC has gone to some >> intermediate logic state which is non-deterministic. >> >> For the LEDs, I would recommend having a 2K series resistor and driving >> from +12 VDC. That works out to around 5mA of current which is enough to >> make many LEDs visibly glow and well-below the 7mA max current rating of >> the 7441. >> >> On Tuesday, September 26, 2023 at 6:30:15 AM UTC-7 Craig Garnett wrote: >> >>> I bought a 74141 on Ebay and I had a bit of trouble with the delivery >>> but it arrived eventually so I'm trying to test it on the breadboard. >>> >>> I've hooked up LEDs from +ve to all the outputs and pulled the 4 address >>> lines down to ground with 100k >>> >>> When I power it up 6 of the LEDS are on and raising any of the address >>> lines does nothing. >>> >>> It doesn't look good does it? >>> >>> Craig >>> >> -- 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 view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/d47c6197-ef26-491b-a3e3-659e40b4f022n%40googlegroups.com.
