Friday, February 27, 2015

Beginning cleaning of final 1132 printer levers, nearly done with rehabilitation


I opened and worked on the clutch detent lever assembly some more and am now satisfied it is working properly. I inspected and tested all 120 clutch dogs (the lever on the side of each print cam disc that will rotate down into a slot on the axle when it has been released, so that the cam will spin around once to print a character). It is time to re-install the guide bar and clutch detent bars on the machine.

What is in awful condition is the set of clutch latch levers that sit at the bottom rear of the clutch cam disc group. These should pivot inward and hold the clutch dog out of its slot untl the clutch latch is released by a push from the solenoid actuated rod. The restoring lever pushes the clutch latch back into position so it can hold the clutch dog and thus stop the disc from making more than one circle of the shaft on each actuation.

Clutch latch levers at bottom, pivoting into the clutch discs
I am going to try to flood the pivots with oil or otherwise clear them, hoping that they begin to move as the should. It would be best if I could lift them (the entire bar of clutch latches) out of the machine as I did with the other lever assemblies, but this requires a ton of additional disassembly first.

Specifically, I would have to disassemble the gear train, remove bearings and lift the cam clutch cylinder with all 120 cams out, then disconnect and lift out all 120 print wheels. Not only a lot of work, but it introduces the need to do timing and adjustments I would rather than disturb unless I absolutely must.
Gear train that would have to be disassembled, along with print wheels, to lift out clutch latch assembly
The print wheel hangers have a pivot that is right on the top, directly accessible for lubrication, which is perfect for my purposes. I don't think I need to remove the print wheel assembly, as a result. It means that the only issue standing between me and a working printer is the set of clutch latch levers.

Pivot bar for clutch levers visible on left, sticky levers pass through guide bar on right
I spent a bit of the afternoon out working on the clutch latch levers. To have better access, I had to remove a bar that provides grooved supports for the spinning cam clutch discs - this had two allen head bolts holding it on. The left bolt was so frozen in place that I was gradually destroying the allen shape in the head, no gripping tools could turn it from the outside, and it was clear I had to do something extraordinary to remove it.

Troublesome allen bolt, before forced removal
The solution was a chisel and hammer, cutting a slight groove on one side of the bolt head, then striking it at a near tangent angle to force it to rotate. I was able to get it turning and remove it the rest of the way with a normal allen wrench. The bar then had to be persuaded to come loose - its locating pins kept it snugged up even boltless.

With the key points on the clutch latch levers being above my access point, the oil will have to be forced upwards against gravity in order to lubricate it. Washing the surfaces with oil is not an option. I had to use a residue free spray cleaner to free up the gunk, after which I will oil the mechanism as best I can.

Even with the spray, it takes time to work each lever until it moves freely enough to work properly. They should all pop out as they have springs to pull them out to the rest or triggered position. When a solenoid activates, its long lever will slip this latch lever off the clutch disc dog, the spring will pop this clutch lever out, and as a result the clutch dog will be pulled into a slot on the clutch disk shaft, spinning it around.

Late in the rotation of a disc, a wider part of the disc circumference will push on the restoring lever, which in turn pushes the clutch latch back up into contact with the clutch dog. That resets the dog out of contact with the spinning shaft, then the detente levers hold the clutch disc in the rest position until it is triggered for a later print operation.

My print wheel hangers are rotating well, so everything is ready for printing once I get these clutch latch levers working smoothly. It took about 20 minutes to get a group of 15 columns moving freely, so about two or two and a half hours more to work through all 120 columns.

I didn't finish this tonight, so more to do tomorrow until I have all 120 of these clutch latch levers working well. A bit tedious but straightforward.

Right-hand group of clutch latch levers freed up and moving well
Perhaps 30 minutes additional will be needed for final oiling of the mechanism and then I can begin reassembly. I feel good about the chances I will have a properly working printer at the end of this effort.


I met with Lyle Bickley, who will help by reading the tape and storing any content in a transferable file in simh (widely used machine simulator) format suitable for use with the IBM 1130 simulator. I can then send it to the owner.


My components came today for the new SAC interface cards - 50 of each resistor in 0805 size surface mount, 100 of the 33uf tantalum capacitors in surface mount 1206 size, 150 BV52 transistors in surface mount SOT-23 size, and 50 1N4148 signal diodes as discrete (wire-through) parts.

I also spent some time verifying and tagging all the signal wire twisted pairs that will go on the new cards, coming from the large cable connector out to the 1130. I completed the first of the old cards, 12 input and 12 output signals, plus 12 input signals from the second old card. There is a third old card plus five extra circuits on an otherwise bare fourth old card; these signal wires should all be labeled correctly, ready for assembly to my new cards.

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