Re: TTL substitute for DTL
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
Re: TTL substitute for DTL
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.
TTL substitute for DTL
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? --Chuck
