Looking for a substitute of mc789ap chip

[neazoi]

hello I need a sabstitute for the mc789ap chip. 74LSxx series if possible. this is a hex inverter but I cannot find any data for it..??

 

[KMoffett]

mc789ap substitute

Are you thinking pin for pin compatible? I don't think there are any, either TTL or CMOS. What are you building... a TV Typewriter?

Ken

 

[neazoi]

Re: mc789ap substitute

Are you thinking pin for pin compatible? I don't think there are any, either TTL or CMOS. What are you building... a TV Typewriter?

Ken

Yes Ken, exactly. A tv typewriter. I am amazed you found it. It seems this chip is not used anywhere else ?
Pin compatibility is not a problem because I am building the thing in bread board.

 

[KMoffett]

Re: mc789ap substitute

If you Google mc789ap, all you get is TV Typewriter articles. I assume this is the plan: https://www.tinaja.com/glib/bdtvtype.pdf
In the Improved ASCII Encoder schematic it looks like the only thing unusual about its use is that two of the inputs are driven by pull-up transistors Q1 and Q2. TTL defaults to high on the inputs and would require a pull-down drive.

Ken

 

[neazoi]

Re: mc789ap substitute

Not exactly, I am going to build the typewriter II which is an enhancement to one.
I think I will go for discrete DTL using transistors and diodes to replace the hex invertersn it should be more difficult.
do you think any general purpose PNP transistor like 2n2907 could replace the obsolete 2n5139?

 

[betwixt]

Re: mc789ap substitute

Times have changed and so has technology!

I have a similar 'TV typewriter' using a PC keyboard and just two other ICs !!

Brian.

 

[neazoi]

Re: mc789ap substitute

Of course.. It is like re-inventing the wheel but it is very good foe educational purposes, so low level, so easy to understand and follow yet has some uses in amateur radio

 

[Steph00]

Re: mc789ap substitute

Check a cross reference site or contact the manufacturer