Yes VCC on 5 and ground on 12 does seem a bit odd. I am in the UK but I need two of them. I'm toying with the idea of getting two from Cricklewood Electronics or using 4028's and MPSA42's which seems like a better idea but it means finding space for 20 transistors on the board.
On Thursday, 28 September 2023 at 11:02:29 UTC+1 Nick Sargeant wrote: > 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/a8bf4016-9cbf-4074-9994-95e8234623e1n%40googlegroups.com.
