There's a common symptom with CD/DVD in 2010 years: disc is not spinning or spins too slowly. Usually, the culprit is always spindle motor, and in many cases it's model JQ24-40H400, JQ24-35I350F, etc. I don't know brand name, but logo is clearly identifiable. Other low quality motors include Mabuchi imitations (Mebochi, Mabochi and other fake spellings). I've seen very few original Mabuchi's fail this way. Very worn Mabuchi's tend to develop a dead spot. If the motor stops at this spot, it won't start spinning again unless manually pushed a bit.
One quick way to diagnose them is, while the player is turned off, quickly push disc support with your finger to make it spin and see its moment of inertia. If it doesn't spin more than one turn, it's bad. If it keeps spinning for a quarter of a second, it may be good. Another way is to measure resistance between terminals. It has to be between 10 and 18Ω. Then turn the shaft a few degrees and measure again. If you find some point with abnormally high or low resistance, it's bad.
Years ago I tried to pour some drops of WD40 inside (from bottom slots) and exercise them at about 6V for a while. Some of them recovered apparently fine, others not, but all failed again too soon.
Many times I tried to open these motors to see the "cancer" with my eyes, but I couldn't find a way to open them properly without damagin them too much so they could be reassembled. Today I've made some simple tools to do this successfully.
First, two steel strips that come from a street sweeper vehicle (yes, a truck with two brushes and an aspirator that cleans the street at my city). The steel leaves that fall apart are a very interesting material to do aid tools. They're 3mm wide and 0.5mm thick. I've made a notch with a file at one end.
Before attempting to pull the bottom cover, you must weaken the 4 spots where the metal case is bent to prevent cover from getting out. I use sharp cutting pliers to bend them out.
After that, I insert the steel strips in bottom cover large slots, taking care not to damage the inner brushes. Then I catch both strips in a bench vice and start to hit the outer case with a hammer, until the cover gets out. If you have removed the 4 bent points, this operation has to be easy and undamaging. Don't insist if it doesn't get out easily, and check again all 4 bent points.
Once opened, I've tried to spot the cause of malfunction. One interesting point is that lack of moment of inertia persists even without bottom cover (that holds the contact brushes and lower bushing), so it seems that the motor cannot spin freely due to electromagnetic self braking, not because of increasing mechanical friction. Looking carefully at the moving contacts (3, with 3 coils) I see that there's a slot or gap between each other. This gap has a deposit of filings from the contacts, produced by brushes erosion!! These filings are of course conductive and make a shortcircuit between coils. Just cleaning these gaps (with a needle and/or toothbrush), the motor spins freely immediately. It's not reassembled yet, but it can be noticed by turning it manually.
Well, these gaps were clean when the motor was new, so even cleaning it will not make it a better motor like a Mabuchi. It'll fail again the same way in a few years. So I've decided to fill the gaps with something, in order to prevent it from filling with conductive particles. I've used SuperGlue3 (cyanoacrylate). After filling the gaps, I've cleaned well the remains of glue that isn't inside the gaps.
To reassemble the bottom cover, it's required to bend the contact brushes, because moving contacts have a white plastic washer on top. To do this, I use another metal strip (from a large cardboard staple) in "U" shape. Insert it into cover slots and turn in proper direction to bend the brushes a bit. Then insert the bottom cover (do a mark with permanent marker before opening to remember original orientation) and remove the U tool.
After this, motor spins fine again, and I've used not a single drop of lubricant, because these motors never needed any oil. Now, how long will it last?
P.D. Please don't tell me "why you just didn't replace the motor?", because this is not the point of this post.
One quick way to diagnose them is, while the player is turned off, quickly push disc support with your finger to make it spin and see its moment of inertia. If it doesn't spin more than one turn, it's bad. If it keeps spinning for a quarter of a second, it may be good. Another way is to measure resistance between terminals. It has to be between 10 and 18Ω. Then turn the shaft a few degrees and measure again. If you find some point with abnormally high or low resistance, it's bad.
Years ago I tried to pour some drops of WD40 inside (from bottom slots) and exercise them at about 6V for a while. Some of them recovered apparently fine, others not, but all failed again too soon.
Many times I tried to open these motors to see the "cancer" with my eyes, but I couldn't find a way to open them properly without damagin them too much so they could be reassembled. Today I've made some simple tools to do this successfully.
First, two steel strips that come from a street sweeper vehicle (yes, a truck with two brushes and an aspirator that cleans the street at my city). The steel leaves that fall apart are a very interesting material to do aid tools. They're 3mm wide and 0.5mm thick. I've made a notch with a file at one end.
Before attempting to pull the bottom cover, you must weaken the 4 spots where the metal case is bent to prevent cover from getting out. I use sharp cutting pliers to bend them out.
After that, I insert the steel strips in bottom cover large slots, taking care not to damage the inner brushes. Then I catch both strips in a bench vice and start to hit the outer case with a hammer, until the cover gets out. If you have removed the 4 bent points, this operation has to be easy and undamaging. Don't insist if it doesn't get out easily, and check again all 4 bent points.
Once opened, I've tried to spot the cause of malfunction. One interesting point is that lack of moment of inertia persists even without bottom cover (that holds the contact brushes and lower bushing), so it seems that the motor cannot spin freely due to electromagnetic self braking, not because of increasing mechanical friction. Looking carefully at the moving contacts (3, with 3 coils) I see that there's a slot or gap between each other. This gap has a deposit of filings from the contacts, produced by brushes erosion!! These filings are of course conductive and make a shortcircuit between coils. Just cleaning these gaps (with a needle and/or toothbrush), the motor spins freely immediately. It's not reassembled yet, but it can be noticed by turning it manually.
Well, these gaps were clean when the motor was new, so even cleaning it will not make it a better motor like a Mabuchi. It'll fail again the same way in a few years. So I've decided to fill the gaps with something, in order to prevent it from filling with conductive particles. I've used SuperGlue3 (cyanoacrylate). After filling the gaps, I've cleaned well the remains of glue that isn't inside the gaps.
To reassemble the bottom cover, it's required to bend the contact brushes, because moving contacts have a white plastic washer on top. To do this, I use another metal strip (from a large cardboard staple) in "U" shape. Insert it into cover slots and turn in proper direction to bend the brushes a bit. Then insert the bottom cover (do a mark with permanent marker before opening to remember original orientation) and remove the U tool.
After this, motor spins fine again, and I've used not a single drop of lubricant, because these motors never needed any oil. Now, how long will it last?
P.D. Please don't tell me "why you just didn't replace the motor?", because this is not the point of this post.
Attached Files
CAPs POOF
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