Saturday, September 5, 2015

1053 pull links done, connected SAC enhancement into 1130 backplanes


I tackled the broken swing-arm pivot screw, looking to put together an equivalent from a longer hex head bolt, nut and a bit of hollow tube around which the swing arm pivots. The original part is a hex head screw with a stepped diameter, the part closest to the head being a smooth cylindrical section to allow rotation and then the stepped down remainder is threaded to match the nut.

The dimensions of the very short hollow tube are important. The outer diameter has to match the pivot arm to allow smooth rotation. The inner must be large enough to allow the hex head bolt through. The length has to be slightly larger than the pivot arm thickness, allowing rotation but not any cocking of the arm to the side. Finally, my bolt has to be a good length, to fit over the hollow tube, through the bracket assembly, and allow the nut to affix but not extend too far past the outer face of the nut.

I picked up a set of hardware from a local store but it was not good enough - outer diameter too small and the threaded part too wide. I will keep at it, until I find a suitable combination. Not sure how the machine will work without the pivot arm and the switch operation, but I will probably find out.

Meanwhile, I attached two more pull links, but one came off. Tedious and extra hard because there is zero visibility to the area where the link attaches, unless I disassemble my shift mechanism and lose those adjustments. I refuse to pay that pound of flesh so it goes slowly.

Finally by early evening, all five pull links are properly attached and releasing the mechanisms when the solenoid arm is activated. I will do some fine tuning of the adjustment pressure but all five are operating pretty well right now.

Fixing the pivot arm attachment and repairing the ribbon color activating tape are left, plus adjustments, testing and cover/faceplate installation. I can see the finish line from here.


I dressed the wiring that runs down inside the 1131 to the backplanes, soldered on push-on ends, and used heat shrink tubing where necessary. Cable ties held the lines neatly as well, allowing for movement with the full swing-out and swing-in positions of the two gate frames. All the lines are pushed onto the respective pins on the backplane.

Push on ends added to the twisted pairs
Example of one twisted pair added to the backplane
I then had to fasten the lines to the fpga in the SAC Interface Box, since they are now wired into the 1130 system. Updated logic was written to the fpga to handle those lines. My python PC side program is updated to display and set the two new interrupt levels, so that I could test my circuit and wiring.

The DC-DC converter board came in today and was wired in. A bench power supply provided the +6V for the converter, whose output was the 5V needed by the daughter card and other boards I have inside the 1131. Since that works, I will wire the converter into the +6V SLT supply lines and mount the converter board in a suitable location.

DC-DC converter in operation converting +6V to +5V
I picked a location to mount the 'emulation engine' board which activates relays in a timed sequence, the relay board that virtually pushes the three buttons, and began to wire everything into place. I have a bit of wiring to do to hook the four relays into their three button circuits, plus the power lines will be finished once I mount the DC-DC converter board somewhere.

Approximate location of the emulation engine and relay boards
If I get the DC-DC converter wired to the SLT power supply and at least the daughter card fully functional, I can do some power-on testing of the system. The Program Load function of the emulation engine and relay board can be finished and tested independently. 


  1. Re the stepped screw, rather than a small tube you might look for small washers with the correct OD and ID (or a too-small ID that could be reamed out). I'm looking at the catalog and they have a number of stainless steel flat washers, maybe a stack of 2 or 3 would do the trick?

  2. The pivot arm has an opening that is 1/4" in diameter, that must rotate smoothly over the shoulder. Thus, I need something with an OD of exactly 1/4" and about 3/64" wide for the arm to pivot on.

    If the shoulder is wider than 3/64, I can use wishers whose ID is at least 1/4" so that the arm has a 3/64" space to match the width of the arm at the pivot.However, the 1/4" diameter smooth OD is the critical dimension.

    If I can find washers that are 1/4" OD and fit a 6-32 bolt with their ID, and that could stack to 3/64" wide with a flat enough surface across the multiple washers to allow the arm to pivot, that indeed would work.

  3. SAE #2 washers are 1/4" OD but their inner diameter, at 3/32", is too small for a 6/32 bolt to fit through. Perhaps if I ream them out 5/32" or a bit less then would work, but then I also need 2.34 of them to make up my 3/64 shoulder as they are 0.02 thick. I could use a smaller diameter thinner washer of some kind along with two of the #2 washers to give me the total of 3/64" I need.

  4. now going for 1/4" OD hollow stainless tubing