More cleaning and checkout of 1130's disk drive; preparing to build my 1627 plotter controller card

REMOVING THICK SLUDGE INSIDE DISK DRIVE

I did some cleaning, discovering thick sludge coating the mechanism. This coating is strange, looking like a cross between the result of years in a heavy cigarette smoking environment and an airborne oily film. This may be a consequence of the mouse infestation but it is different from what I saw elsewhere in the 1130. 

CHECKING HEAD AND PLATTER ALIGNMENT

Because I was uncertain about the position of the lower arm I partially assembled the receiver that guides the cartridge into the drive and holds it in place. I then slid a cartridge in carefully while checking for clearance and alignment. 

You can see in the picture that a pivoting metal part will push the cartridge cover apart, exposing the platter and allowing the disk heads to enter on either side of the disk surface. I advanced slowly and looked at the alignment of the heads relative to the platter.

The heads are held apart so that the platter will slide between them, with a safe gap between the heads and the surface. The head loading solenoid will press the heads from the back, forcing them down onto the disk surface once the drive is rotating at full speed (1500 rpm). 

The cartridge was moved forward a bit more letting me see how the platter sits between the heads. All good so far. 

A closeup view verifies that they will not be rubbing on the disk surface when a cartridge is first inserted. This is also important as the virtual 2315 cartridge facility that will be installed on this machine will leave the heads up safely above the disk surface, while moving the arms in and out during disk accesses. We want them to never impact the disk surface, which the gap guarantees. 

ODD GUMMY RESIDUE ON DISK DRIVE HANDLE - HARD TO REMOVE

The front of the drive has a large blue handle that is swung down to place a cartridge into the drive and then rotated upward to lock it in place. The front of the handle has some gummy material that I am having difficulty removing. It smears around, like a mix of oil and tape adhesive. It is a bit like the residue sometimes left behind when a stick on label has fallen off of a surface but the glue remains. 

I spent about an hour attacking it with various cleaners such as isopropanol, 409 and Simple Green. The latter cleaner seems to loosen it a bit so that I can rub paper towels in one direction to pull off a layer at a time. It is not done but I expect that with some more elbow grease I will restore the handle to its normal glossy plastic surface, sans residue. 

INTEGRATION OF MY SUBSTITUTE 5806223 CARD FOR 1627 PLOTTER

Several museums have 1627 (or Calcomp) plotters, as do I, but none of us had the controller logic built into our machines. According to the ALDs, this is contained in a single SLT card (double slot sized), 5806223. In addition to the card, there will need to be a cable from the logic compartment to the SMS card interface which hosts some device connections - console printer, paper tape and 1627. 

I recreated the logic of the IBM SLT card using modern components and fit them onto a PCB which will fit atop a double sized SLT card. Two holes in the PCB will allow mounting hardware to attach it firmly to the SLT card which will host it. I provided pads on the edge of the PCB where wires will bridge the signals to the SLT card connector pins. 

WHILE WAITING FOR PCB, PREPARED THE HOST SLT CARD IT WILL MOUNT ON

I found a double size SLT card in my junk/donor pile that has traces to every single pin, important since the IBM card uses every single pin for something. It was also set up so that it will be easy to tack on a wire to the host card that carries the signal for my PCB sitting atop the card. 

I removed all the components on the card - saving them for future repairs or projects. 

The bare board still had patterns connecting pins to locations on the card where parts were installed, some of which might connect pins in a way I don't want. I therefore cut every trace to isolate the landing pads for all pins from the remainder of the card. 

When my PCB arrives, I will mark and drill the two holes that will mechanically hold my PCB on top of the now empty host card. The PCB will be built, mounted, and the bridge wires installed to connect the PCB to all the pins of the host card. I can then bench test this before doing a trial inside the 1130 to see if it will work properly to drive a 1627 plotter.