On 2/10/22 22:39, Brent Hilpert wrote: > On 2022-Feb-10, at 9:50 PM, Chuck Guzis via cctalk wrote: > >> I've got a piece of gear here with a bad MC858P used as a bus >> driver--terminated in 220/330 ohms at the far end. >> >> Given that old DTL is a hit-or-miss proposition, I'm proposing to >> substitute a 7438 OC buffer. Pinout's the same, as is Vcc. >> >> Before I get out the soldering iron, any "don't do it" thoughts? > > > Are you sure the pinouts match? The Moto book I'm looking at indicates the > 858 gates are 'pointing to the middle' (outputs:3,4,10,11) in contrast to the > 7438 common 'all gates pointing to the right' (outputs:3,6,8,11). > > I've replaced DTL with TTL on occasion or two in the past. They're both > current-sinking logic so they work together well enough as far as > output-input drive.
Close enough--using an SOIC-to-DIP breakout board, swap pins 8-10 and 6-4 and Bob should be your uncle. Use 7438 SOIC, of course. At least I believe that should work. Prices for NOS DTL are predictably crazy. --Chuck
