Sunday, February 22, 2015

SAC Interface diagnosis, data center construction and progress restoring the 1132 line printer


1132 Printer before removal of magnet assembly
Magnet Assembly removed
Solenoids on top, pivoting latches across bottom
During cleaning and relubrication
Sticky pivoting latches - the last few before they were all rehabilitated
I now have freed up all the pivoting latches and other parts on the magnet assembly. It is time to turn my attention to the cam, dog, restoring latch and detents, plus the print wheel hanger pivots. These are less accessible, making the work a bit more cumbersome, but whether this is easily repaired or whether I have to do major disassembly will not be determined until I do some cleaning work.

Restoring  and detente latches, cam hidden behind across top, print wheels hidden across bottom
Print wheels barely visible across bottom, totally inked up

I tried a larger capacitance across the base resistor, which added delay to the output of my circuit (bad) without ameliorating the phantom early pulse at all. I moved the scope around in the circuits and discovered that my phantom pulse is induced just as the input line is activated on the next circuit over sequentially. The circuits are packed 12 across on a board, with the output of one stage unfortunately just next to the input of the next one.

It appeared that my phantom signal is induced on the output line, not driven by the transistor. Disconnecting the incoming signal from the adjacent circuit did not, however, fix the problem. I turned my attention to the condition of the power rails and ground, where I saw enough disturbance to warrant some local capacitors on the board itself. I stuck on some 50-70 uf capacitors on the rails and my phantom pulse has gone away.

It would be a pain to add capacitors on all four boards, with them wired in place as they are, and now that I am replacing the fpga board with the new one on order from ZTEX, the existing wiring would have to change anyway. Thus, I am going to bite the bullet, design and have fabricated nice PCBs to assemble the circuits correctly.


I hung the load center box under one of the plastic shelves, routed and hung the outlet boxes and light switch, then dressed some of the cable along the walls. Once I install the lighting this will be ready to go.

I spent some time drilling and tapping the heat sinks to build another lighting module. After testing it, I mounted it in the shed, just a bit more before it is wired in and ready to go.

I decided to move my 1130 replica out to the shed, leaving more room for restoration work in my garage. Once the 1130 system is ready to take its place in the datacenter shed, the replica will come back to my workshop. The frame had some unfinished sheet metal on it, which I let get a bit rusted up outdoors over the last few months, but most of the replica are final parts - the console typewriter mechanism, keyboard, main switches and lights, pedestal display panel, and the front tabletop.

1130 Replica components roughly placed on frame

1130 replica in data center shed showing fit for real 1130
I was building my 1130 as the shorter configuration, up to 8K of 3.6us memory, while the actual 1130 I own has the memory 'blister' on the left side that can support up to 32KW of either 3.6 or 2.2us memory. Still, you can see from the picture that the datacenter shed will accommodate the entire running system, plus card/disk cabinets and the 029 keypunch. It may be cozy, but workable. 

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