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Quote from: Homepin on December 08, 2010, 04:44:17 PMOne of the IC types used on this board is a CA3081 which is practically impossible to find these days and there are seven of them on this board! In reality this IC is made up of 7 pretty common transistors manufactured into a single IC package for ease of production assembly.By replacing each of these IC's on this new board it can then be assembled using common transistors such as BC547's etc. This means the end user will need to install a total of 49 individual transistors but that is far better than trying to locate obsolete devices. It also makes fault finding in the future a lot easier. You can see that IC26 has been replaced here with 7 transistors (ringed in white). Six more to go.........We did investigate that concept but dismissed it because there are seven of these chips on the board. To hang seven 'daughter boards' off the mainboard is simply asking for unreliability issues. At the end of the day they are simply BC547 transistors anyway so it's not really a problem.The bottom line is that we may end up having to supply the parts to build the majority of these blank boards and it will be impossible for us to find 700 of these chips - BC547's are available anywhere and are dirt cheap!This is just one of the changes we feel must be made for this project to be worthwhile in order to keep these machines going.Maybe you could do a small mod board Mike to replace the CA3081 for people that need this chip but cant find it.ian
One of the IC types used on this board is a CA3081 which is practically impossible to find these days and there are seven of them on this board! In reality this IC is made up of 7 pretty common transistors manufactured into a single IC package for ease of production assembly.By replacing each of these IC's on this new board it can then be assembled using common transistors such as BC547's etc. This means the end user will need to install a total of 49 individual transistors but that is far better than trying to locate obsolete devices. It also makes fault finding in the future a lot easier. You can see that IC26 has been replaced here with 7 transistors (ringed in white). Six more to go.........We did investigate that concept but dismissed it because there are seven of these chips on the board. To hang seven 'daughter boards' off the mainboard is simply asking for unreliability issues. At the end of the day they are simply BC547 transistors anyway so it's not really a problem.The bottom line is that we may end up having to supply the parts to build the majority of these blank boards and it will be impossible for us to find 700 of these chips - BC547's are available anywhere and are dirt cheap!This is just one of the changes we feel must be made for this project to be worthwhile in order to keep these machines going.
