On 21/12/2016 00:58, "Paul Berger" <[email protected]> wrote:
> On 2016-12-20 8:50 PM, Adrian Graham wrote: >> Evening folks, >> >> (it's evening here) >> >> Typically for troubleshooting around $FESTIVAL I find a more-than-likely >> dead MC14081B (CMOS quad dual-input AND gates) just as UK postage ends for >> the next few days so getting a replacement won't happen until next week. >> >> Question is, aside from having to make up an adapter board to change the >> pins around and making sure Vcc is +5V is there any reason I can't use >> something like a 74LS08 for testing? One of the outputs is RESET for an >> 8085A so nothing too demanding. > If one of the other outputs is driving a CMOS device the output may not > go high enough to satisfy it, however I would expect the reset input on > the 8085A to be TTL compatible. Out of 4 outputs 2 are fed back into itself as inputs, one goes off to RESET via a 74LS04N and the 4th disappears into the phone side of things possibly to an Intel D8741A as well as seemingly being used as a base driver for a BC548 transistor. Inputs are from a 5V-fed resistor network and Vcc for all 3 CMOS chips comes from a 12V line via a 1kohm resistor. Tonight I'll make sure all the verdegris'd resistors and caps are ok. The 8085's arrived yesterday too, thanks! -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?
