TTL substitute for DTL

[Chuck Guzis]

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