It is most likely an off brown, marking a 1% and not violet. Sometimes their paints change with age.
Dwight ________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Adrian Graham <wit...@binarydinosaurs.co.uk> Sent: Saturday, December 17, 2016 10:34:01 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Re: Mystery 8085-related IC identification needed please On 17/12/2016 14:28, "Tony Duell" <ard.p850...@gmail.com> wrote: > On Sat, Dec 17, 2016 at 2:02 PM, Adrian Graham > <wit...@binarydinosaurs.co.uk> wrote: >> > >> >> Thanks all, the pinouts are matching the LS9x counters so I just need to >> trace more lines to hopefully narrow it down. Pins 6 and 7 are definitely >> inputs so you're right Tony, the reset must come from elsewhere. One of the >> outputs is confusing though since it appears to come FROM 5V via a resistor, > > What value resistor? It's a 5-band red-red-black-black-violet so either 220R or 70k? Based on what Pete said about the Z80 I'm going for 220R without pulling it out of circuit. > It is possible that whatever it is driving needs a swing to +5V, > rather than just > a TTL high level. Adding a pull-up resistor is a way to kludge this. I thought that but it doesn't appear to go anywhere else. I'll keep looking, its only a 2 layer board so there's nothing hidden. > The 7490 has 2 sets of reset inputs (4 pins total), one pair to reset > it to 0, the > other pair to reset it to 9. Since these inputs are active high, they > can't be left > floating, they must be conneccted to something (even if directly to ground). > So > you could see if those pins go anywhwere, if not, then you can eliminate the > 7490 One problem I have is that I've already found a few chips with dead outputs so I've no idea if these will be any different. The pinouts I have match the LS92 since pins 2/3/4/13 are NC. All testing so far has been done with a DMM and cheap logic analyser. Since one of the possibly-LS92s is out of circuit I'll build a little test circuit to see if it does actually count given a clock source... Cheers! -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?