UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

emeritus · 23rd Feb 2021, 10:52 pm

The datasheet also has the military flatpack version, same electrical spec as the 5400 version. The custom ICs I was designing at that time were mounted in that type of military flat pack, which I believe pre-dated the DIL package and were possibly the first type of SMD. AFAIR the empty packages (ceramic frame and gold plated base and cover) cost 50p each in 1973 money, about the same as the silicon chip that was mounted in them, subsequently increasedy by the savage inflation of the time. One of our team had a resin encapsulation kit and we used it to turn some of the failures into ear-rings and pendants!

My first encounter with TTL was in 1967 as a student at Plessey, when I was given the task of hard wiring a dozen or so ICs with point to point wiring that provided time multiplexing for a 28V avionics warning indicator: guess who got the 5V and 28V lines transposed! All the ceramic 54xx TTL (SGS-Fairchild and TI) survived the more than 500% overvoltage, all the plastic 74xx ones (mostly Ferranti) died. Fortunately sockets were used so replacement was simple.

23rd Feb 2021, 10:52 pm	#13
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,339	Re: Plastic or ceramic ICs? The datasheet also has the military flatpack version, same electrical spec as the 5400 version. The custom ICs I was designing at that time were mounted in that type of military flat pack, which I believe pre-dated the DIL package and were possibly the first type of SMD. AFAIR the empty packages (ceramic frame and gold plated base and cover) cost 50p each in 1973 money, about the same as the silicon chip that was mounted in them, subsequently increasedy by the savage inflation of the time. One of our team had a resin encapsulation kit and we used it to turn some of the failures into ear-rings and pendants! My first encounter with TTL was in 1967 as a student at Plessey, when I was given the task of hard wiring a dozen or so ICs with point to point wiring that provided time multiplexing for a 28V avionics warning indicator: guess who got the 5V and 28V lines transposed! All the ceramic 54xx TTL (SGS-Fairchild and TI) survived the more than 500% overvoltage, all the plastic 74xx ones (mostly Ferranti) died. Fortunately sockets were used so replacement was simple. Last edited by emeritus; 23rd Feb 2021 at 11:22 pm.