Need help with SYSTEM 80b Chip numbers?

[ddstoys]

Hi Just looking at the system 80b machines and have a few dodgy looking chips on the cpu and by clays tests they may be the problem.

 The chip stated on the CPU diagram is a SN7400n  i have some new chips here which are sn74ls00  are these chips suitable?  Ive tried looking up the data sheets and there both on the one sheet but they mean nothing to me?

 Any help would be great dont even know where i got these chips from but there still in the chip tubes so i must have bought them new and would be great to use em if i can.

[studley67]

i have a sys80b for sale at the moment .if you need any info let me know befor its gone. regards damien

[ajlaird]

Hi Just looking at the system 80b machines and have a few dodgy looking chips on the cpu and by clays tests they may be the problem.

 The chip stated on the CPU diagram is a SN7400n  i have some new chips here which are sn74ls00  are these chips suitable?  Ive tried looking up the data sheets and there both on the one sheet but they mean nothing to me?

 Any help would be great dont even know where i got these chips from but there still in the chip tubes so i must have bought them new and would be great to use em if i can.

You may need to be careful as the output drive on the SN7400N is double that of the SN74LS00 (16ma vs 8ma) so if the output is being maxed out you will run into problems with the LS model. Depends where the output goes.

[ddstoys]

So it will work if it can handle the power of what ever its driving?

[ajlaird]

So it will work if it can handle the power of what ever its driving?

Yeah, should do; both use the same voltages and both are TTL logic and both should have identical pinouts (I didn't check this, just assumed it was the case).

[ddstoys]

Yeah the pinouts are that same. Thanks for your help ill try using em if they fix the problem ill order in the proper ones

[ajlaird]

Without it working, this might be difficult, but you could measure the current on the output pins of the existing chips. If it's more than 8ma you won't be able to use the LS chips.

[Strangeways]

ICs are cheap, system 80 boards are expensive. I ALWAYS replace the part as specified by the original board confirmed by the schematics.

[ddstoys]

Yeah Good advice Nino
                                     Will use the specified chips not worth all the work if there not going to cope. Just wanted an excuse to get rid of them lol

[The pinballist formally known as Dean Morgan]

74LS00 should be Ok

[ddstoys]

Hey Dean
                Just pulled the board out and noticed that most of the chips in it already are the 74ls00 im just going to remove any suspect looking chips and put in chip sockets so ic an change them easily if need be

[The pinballist formally known as Dean Morgan]

Hey Dean
                Just pulled the board out and noticed that most of the chips in it already are the 74ls00 im just going to remove any suspect looking chips and put in chip sockets so ic an change them easily if need be

Great idea,  I always socket everything I replace to save soldering again if they ever need replacment in the future.

[ddstoys]

Ive been using the machined Socket Strips that you can cut to any size there great saves having a million of each size lying around

[ajlaird]

I've got a bunch of 6 and 8 pin sockets. If you solder them in end on end you can make just about whatever you need.

[ddstoys]

Also a great idea might use up my remaining sockets that way