Disk drive on bench, raw DC power supply on bench, no new issues found

I FINISHED UNMOUNTING THE DISK DRIVE AND MOVED IT TO THE WORKBENCH

I have great access now to the disk drive for cleaning and restoration. As a bonus, this opens up the congested area of the 1130 where power and signal wiring is clustered. It allowed me to look over all the wiring for any signs of damage; it appears that the only gnawing took place in the power box (sequencer box).

Mess of wiring in the base

Space to look at all the wiring

COULD SEE THAT THE RAW DC POWER SUPPLY WAS ALSO IMPACTED

As you can see when looking at the back of the raw supply, it is open and I could see quite a bit of dirt inside. The top grate has holes which would allow rodent urine to enter, but with the rear wide open there was the chance that mice entered and did some chewing.  

RAW POWER SUPPLY PULLED AND PUT ON WORKBENCH; FILTHY INSIDE

I unwired the supply, removed it and had it on the workbench for a full inspection. It looked terrible in there, dirty stains covering the parts as well as bits of mouse bedding and plenty of plain old dirt sitting in the bottom and atop everything. 

Even more room now

READY FOR THE SEQUENCING BOX REWIRING

I picked up 12 gauge stranded wire in both black and white insulation colors, which should give me enough to rebuild all the damaged wire bundles in the machine. I anticipate that in a day or two I will get into the sequencing box itself, documenting and removing the damaged existing bundles. With those in hand, I can build good replacements. 

STARTING TO CLEAN AND CHECK ALL THE COMPONENTS INSIDE RAW DC SUPPLY

I began to remove components, cleaning them and checking the capacitors for signs of problems. The disgusting state of everything in the power supply enclosure made this an unpleasant task indeed. I could get the majority of the stains and dirt off the components with some 409 and elbow grease and lots of paper towels. 

Right one before cleaning, left after some scrubbing

My capacitance meter showed all the capacitors were at or substantially above the specified values. I did a quick ESR check on a couple and they seemed acceptable. This has been my experience with the capacitors used in IBM equipment built in the 1950s and 1960s - age has no effect on them at all. 

I then inspected one of the two transformers for any signs of damage to the windings. It appears to be in great shape, other than some surface rust on the laminated iron plates. I did a bit of cleaning of loose rust from the laminates but I won't clean them any more aggressively. That would risk introducing conductivity between laminate plates, which causes parasitic eddy currents and heating of the transformer. 

BATTLING WITH LINE FILTER AND POWER CORD STUB

The connector body where the severed stub of the power cord enters the line filter box is so corroded that I couldn't unscrew it properly. I am also having difficulty getting the line filter box out of the machine for inspection. The parts catalog suggests that it is bolted to the machine bottom from the inside of the box. Since I see no way to get into the box as it sits, I could only turn the nuts under the machine. These turned a couple of rotations and then seemed to be winding wiring because the resistance to turning went up fast. 

Line filter under the wires

It is likely that I will remove this entirely and substitute a modern line filter in a metal electrical box. Line filters are only around $25 and I won't be dealing with corroded parts. 

SOON - THE SEQUENCER BOX ITSELF

Top of sequencer box, mice chewed through rear

The bundle of wires you can see above going to the rear of the sequencer box are mostly connected to the terminal blocks on the rear. Other connections to the terminal block run inside the box and those are the wires which were gnawed by mice.