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.
