MAGNET ASSEMBLY WORK
I worked on the Magnet Assembly with my trusty Nye oil. That has the Link and the Armature Knockoff Lever components on it, plus the plate with the print magnets that will pull on the Link. I oiled the pivot points and the slots that align the parts. Initially they were frozen solid. I would get a small group of them moving each time, at first barely moving at all but eventually crisply snapping back under spring power.
About 1 in 10 of the levers would still be sticky, restoring very slowly when I move it. It took extra time and manipulation to get those to perform properly. The picture below is at a point where I was working from right to left through the levers but hadn't finished.
The armatures of the print magnets were all working well already, as they had not been previously lubricated. Thus once I had the Magnet Assembly restored, it was time to move on to the rest of the print mechanism. Looking down from the top, you can see the Print Cams and related parts visible.
In the picture above, you can see the Print Cam Detent parts engaged with the notch in the Print Cams above. The Print Cam Detents are held in place by a machined bar sitting across the front of the printer frame.
The Print Cams rotate around the 18 flute shaft - just visible in the picture below taken from the right side of the cams.
MISSING PRINT CAM DETENT IN COLUMN 120 - PREVIOUS FAILURE
I had previously noticed a gouge in the platen over on the right side. Seeing the missing Print Cam Detent and partially disabled Print Cam tells me that a part failed, it jammed into the platen, and somebody shuffled the good parts to the left so that only column 120 is dead. Above you can see the missing parts on the right. Below you can see the gouged platen.
MORE DAMAGE DETECTED - NEED A RUBBER BELT
One of the two rubber drive belts had a big cut in it. It will fail soon and needs to be replaced.
The pulley that this belt turns rotates the Print Cam Shaft. A passive gear just below it couples the rotation onto the drive gear that turns the 120 Print Wheels.
The drive gear turning the Print Wheels has the timing disk on the end of the shaft. A lamp shines through the disk onto photocells that detect holes in concentric circles as the disk spins. The outer circle has 48 holes evenly spaced around the disk which provide timing pulses for the arrival of each character on the Print Wheels. The seven inner circles have holes that define the code for the character so that when the CPU reads the code it knows which print magnets to fire to put that character on the paper.
REMOVING BAR WITH PRINT CAM DETENT LEVERS FOR RESTORATION
The machined bar for the Print Cam Detents is secured to the frame by two bolts and one pin on each side. Unfortunately, the passive gear is right in the way, blocking removal of one of the four bolts and one pin.
I had to remove the circlip and nudge the passive gear partially off its shaft in order to get the machined bar out of the machine. It will need to be worked carefully with the Nye oil to free up the 119 levers.
Below that machined bar sat another one, holding the Print Cam Restore levers. It also has four bolts and two pins holding it in place, but in addition had two socket head bolts through a slotted guide plate above.
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