I have adjusted dozens of yokes over the years. You can't adjust the yoke from the controls on the back of the Classic above the power switch (although there are plenty more settings there than on the analog boards of earlier Macs).
Here's what to do:
1. Open the Mac.
2. Set it upright on a non-carpet surface.
3. Loosen the Phillips head screws around the CRT.
4. Plug in and turn on the Mac.
5. Turn the coiled wires, making sure you avoid the red anode cap (which looks like a suction cup) at all costs.
6. When the desired position has been reached, turn off the Mac and tighten the screws. Make sure you don't bump what you just adjusted, or else your work will be undone.
7. Check the screen to make sure it's good.
8. Check your screws again to make sure they're tight.
9. Put the case back on the Mac.
A few points to keep in mind:
1. Avoid the anode cap at all costs.
2. Don't bump the centering rings (the little solid golden-colored rings that go around the CRT).
3. Don't bump the magnets around the neck of the CRT unless you want to mess up your geometry.
4. Avoid touching anything on the analog board.
5. You may want to adjust the size of the horizontal and vertical raster before working on the centering to make things easier. You can do this through the controls on the back of the Mac. TV adjustment tools should do the trick with these holes (you can get these at Radio Shack or online) or you can use a small screwdriver.
6. Keep in mind that the top and bottom may not align perfectly. These are CRTs, not LCDs, and all CRTs have slight geometry imperfections.
7. If you're afraid of reaching around to the back of the Mac from the front, put a mirror in front of it. Many CRT newbies do this trick until they gain more confidence in their adjustment and accident avoidance abilities. Avoid the bathroom, of course, as water and Macs don't mix.
8. HAVE FAITH IN YOURSELF!!! Many people don't attempt to do this repair because they are scared of the high voltages. However, it's really a simple fix and as long as you know what not to touch you should be OK!!!
Best of luck with the adjustment!!! Let us know how it turns out!!!
Here's what to do:
1. Open the Mac.
2. Set it upright on a non-carpet surface.
3. Loosen the Phillips head screws around the CRT.
4. Plug in and turn on the Mac.
5. Turn the coiled wires, making sure you avoid the red anode cap (which looks like a suction cup) at all costs.
6. When the desired position has been reached, turn off the Mac and tighten the screws. Make sure you don't bump what you just adjusted, or else your work will be undone.
7. Check the screen to make sure it's good.
8. Check your screws again to make sure they're tight.
9. Put the case back on the Mac.
A few points to keep in mind:
1. Avoid the anode cap at all costs.
2. Don't bump the centering rings (the little solid golden-colored rings that go around the CRT).
3. Don't bump the magnets around the neck of the CRT unless you want to mess up your geometry.
4. Avoid touching anything on the analog board.
5. You may want to adjust the size of the horizontal and vertical raster before working on the centering to make things easier. You can do this through the controls on the back of the Mac. TV adjustment tools should do the trick with these holes (you can get these at Radio Shack or online) or you can use a small screwdriver.
6. Keep in mind that the top and bottom may not align perfectly. These are CRTs, not LCDs, and all CRTs have slight geometry imperfections.
7. If you're afraid of reaching around to the back of the Mac from the front, put a mirror in front of it. Many CRT newbies do this trick until they gain more confidence in their adjustment and accident avoidance abilities. Avoid the bathroom, of course, as water and Macs don't mix.
8. HAVE FAITH IN YOURSELF!!! Many people don't attempt to do this repair because they are scared of the high voltages. However, it's really a simple fix and as long as you know what not to touch you should be OK!!!
Best of luck with the adjustment!!! Let us know how it turns out!!!