Huge IBM 1800 find (and need some help)

On 03/21/2015 01:47 PM, Johannes Thelen wrote: You have to be very careful with anything that requires temperature extremes. Can anybody verify the 2311 uses the hydraulic head positioner? If the oxide coating of the packs has deteriorated, which I think is quite possible, then the disks will not be usable. Anybody else have experience with 14" disk packs from 40" years ago? The other problem is this machine uses SLT. That was never a super-reliable technology. They start with 1/2" square ceramic substrates, and fire thin film resistors onto them, then print and fire thick film wiring. Then they use bump-bonded discrete transistors and diodes, and solder these by bump bonds to the wiring, and add leads. Then, because the transistors and diodes are not well-passivated, they smear silicone goop over it and epoxy on the die-drawn aluminum covers. These are not totally hermetic, and oxygen gets inside and slowly deteriorates the semiconductor devices. They also had some problems with the solder joints to them developing cracks. So, the likelihood of the CPU actually working after FORTY years of storage is pretty small. There are, of course, no replacements for SLT modules, as IBM stopped making them in the late 1960's! It was a form of diode-transistor logic, and not terribly dense. A single flip-flop would not fit in one SLT module, it took at least 2, and the usual scheme was to integrate some steering gates with it and ended up with about 4 modules to implement the typical register bit. They didn't use what we think of today as a FF, they used D latches, as it was simpler to implement, but required several clock phases. One clock phase to latch input data to the ALU, wait for the ALU to settle, then a pulse to latch the result out of the ALU. I wouldn't worry about what is left in core, it would be interesting, but you might have to do a lot of testing and repair before enough of the machine is working to read it out. Be very careful with the disk drives. If you even get a scratch on the heads, you will not be able to replace them. Also, if anything at all happens to the heads, you will need an alignment pack to realign any replaced heads. Do you have ANY experience with old-school mainframe equipment? If you think you will just dust this thing off, mount the disk packs and fire it up, you are quite crazy! Jon