I think I'd agree. I've used the Russian K155ID1 drivers from eBay which seem to work OK (after finding out the first Eagle library I used had the power supply pins swapped so VCC was on pin 12 - reminded me to check new library symbols every time now) but it's clearly been a long time, since they seem to be silly money now. I repaired my HP 5326A with one of those on a small daughter board plugged in to where the HP custom chip lived. Not that I use it as my daily driver any more, since the fan is too noisy. If you lived in UK, I could post you one for grins - assuming I can find one in the parts bins.
On Thursday, 28 September 2023 at 09:17:53 UTC+1 Craig Garnett wrote: > That didn't work either, I think I've been sold a duff one. > > Craig > > On Wednesday, 27 September 2023 at 14:30:22 UTC+1 Craig Garnett wrote: > >> Thanks Nick, I'll try that. >> Back in my day I mostly used 4000 CMOS, I didn't do much with TTL. >> >> On Wednesday, 27 September 2023 at 11:23:17 UTC+1 Nick Sargeant wrote: >> >>> I'd agree with the above. To make sure you are avoiding any >>> indeterminate states, pull all of the inputs up to +5v with a resistor of >>> about 2k2 to 4k7. Then, for the inputs you want low, jumper those inputs to >>> ground. The pull-up resistors will mean you get a good solid '1' without >>> the jumper, and a good '0' with a jumper to ground. >>> >>> When designing with TTL,back in the day, we tended to work with negative >>> logic as a preference, because of the nature of the inputs being connected >>> to the emitters of bipolar transistors. >>> >>> >>> >>> On Wednesday, 27 September 2023 at 10:14:46 UTC+1 Craig Garnett wrote: >>> >>>> 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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/6b0eea2b-f473-4a48-9809-88316e999a70n%40googlegroups.com.
