Turbo Grafx CD Gear Cleaning

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1990 was a long time ago!

Nomenclature

It should be known that I've made up some terms here to describe various bits and bobs. If you see something with an incorrect or imprecise name, please shoot me a message so I can correct it!


Laser Sled Gears

  • Gears and gear shaft arrangement:
    • Shaft 1:
      • Motor
      • Spur gear attached to motor output shaft
    • Shaft 2:
      • Metal bushing
      • Cluster gear / Middle Gear (Broken?)
      • Retaining clip
    • Shaft 3:
      • Nylon top hat bushing
      • Brass worm gear
      • Nylon retaining bushing
      • Nylon spur gear


Step 0: Open the CD-ROM drive

This step is fairly trivial:

4 screws hold the bottom case on

You may choose to desolder the ground wire to the bottom case. If you don't, it will probably fall off on its own later on anyway. You might as well remove it now so you still feel like you're the one calling the shots around here.

1 screw holds the PCB to the upper case

Unlock and disconnect the 2 ribbon cables leading to the laser assembly. You can now move the PCB out of the way and access the CD mechanism.

Step 1: Look Around You

Step 1

Get to know your Turbo Grafx CD drive. Let it know not to be frightened, that while you may inadvertently slaughter it during this process, you only have the best of intentions.





Step 2: Remove The Limit Switch and Gear Retainer

Step 2

A single screw removes the switch. Then remove the brass-looking L-shaped doo-dad that keeps the worm gear in check.





Step 3: Remove the split ring and cluster gear

Step 3

This step can make or break the rest of your journey. Instead of using a C or E clip, NEC chose this minuscule split washer to hold the cluster gear in place. Failing to use a gentle touch can send this thing flying across the room, never to be seen again. Also, avoid levering against the cluster gear, as it's delicate, and may already be broken.

If your middle gear is already broken, replacements are available!

Step 4: Remove the assembly from the upper case

Step 4

3 brass screws hold the laser assembly to the upper case. Remove them, along with the brass ferrules. The screw nearest the motor has a single black washer, too. Underneath that shock absorber is a plastic washer, which may or may not stay in place once the laser assembly is removed.

Step 5: Remove the finishing plate

Step 5

Finishing plate? Fascia? Anybody know the right word for this thing? Basically it's the large black trim piece that hides everything but the laser eye and the spindle. Remove the 2 tiny screws, then unclip it from the side of the frame. Beware the grounding wire or you'll have to solder it back on later.

Be absolutely sure not to flex or bend this plate or it may rub against CDs, scuffing your precious copy of Ai Cho Aniki.

Step 6: Remove the worm gear follower

Step 6

A single screw retains the follower.





Step 7: Remove motor screw & metal blocking plate

Step 7

One of the screws that holds the motor in place also holds a metal blocking plate in place. Remove the screw & plate.

This screw may be seized up and difficult to remove. Be absolutely sure to use the proper Phillips head. Rather than just muscling it out, rock the screwdriver back and forth to simulate an impact wrench. If your screwdriver cams out out the screw head even a couple of times, it will probably wear the head down far enough to make things really difficult.





Step 8: Unclip the retaining bushing

Step 8

This should come loose with minimal effort.





Step 9: Remove the top hat bushing and worm gear

Step 9

Slide the worm gear out a little bit. If the top hat bushing stays in place, the worm gear can be fully removed. If the top hat bushing is attached, you'll have to remove it before it will clear the laser.





Step 10: Clean and relube!

Step 10

Remove all traces of the old lubricant. Use a mild degreasing cleaner, like 409, Simple Green, dish soap, or something that won't eat your tasty plastic parts. Clean the cluster gear shaft, and the worm follower, both the follower that you removed, and the rest of the nylon follower assembly that's still attached to the laser. Clean the top hat bushing and the retaining bushing.

Lubricate these parts:

  • Worm gear and follower
  • Laser sled rail

Do not lubricate these parts:

  • Motor / Cluster gear - these weren't greased at the factory and should not be greased now. Grease will actually prevent these parts from turning smoothly and course tracking will suck.
  • Top hat bushing - grease here will trap an air bubble and prevent the whole worm gear from sliding slightly as designed.

Lubricants that are safe for VCR should be good, be they silicone or a calcium stearate-based grease like Luberex. Don't use automotive lubricants, 3-in-1 or other light oils. You need something that will stay in place and not dissolve the nylon.


Step 11: Reassemble.

Assembly is pretty much the reverse of disassembly.

Referring to this image: TG16-CD-Gears---08-Motor-screw-and-blocking-plate.jpg, when reinstalling the metal plate, align it as shown in this photo, otherwise it can rub against the worm/spur gear.

When reattaching the worm gear follower, be sure to center it as best as possible. If it's rotated slightly it may have more of a tendency to skip out of gear and make a buzzing noise during fast laser seeks. Slowly tighten the screw that holds the follower while lightly moving the sled back and forth. As the screw is snugged down, this will help auto-center it onto the worm gear.