This guide describes how to replace the “chuck in” microswitch on the Sony MDS-JE500 and MDS-510. Other units may be affected by this, please update the wiki for any additional models affected by this issue.

Models with this issue will continuously attempt to eject an otherwise empty mechanism potentially leading to grinding gears and long term damage. Generally, placing a disk into the device will allow it to behave normally.

There are guides out there that will have you bend a tab so that it lands on the microswitch differently. I don't recommend this trick as it is short lived and the switch will quickly wear out in the new spot. Replacing the switch completely is best way to ensure you have a long lasting fix.

To perform this repair you will need basic tools including multiple phillips screw driver tips, soldering iron and replacement microswitches. This switch (the SDS-004) available at [https://www.digikey.com/short/15tn9f74/ ] is an exact but improved replacement part. This same part is used for the “chuck in” switch as well as the laser sled to indicate it is in the fully “in” position.

• Unplug the device and then remove the top. You will find five screws, one in the back and two on each side.
• Carefully unplug the two ribbon cables that connect to the MD mechanism

• You will find it easier later if you bring the loading mechanism in partially. Do this with the front of the player facing you. You will find a curved metal part with teeth on it (see photo below) that can be pressed to the right. While this is pressed in, spin the gear with the holes in it counter-clockwise until the sled moves in enough to lock the lever you are pressing into place.
• Remove the four screws that secure the MD mechanism to the chassis

• Lift the MD mechanism out of the chassis
• Remove the two white ribbon cables and set them aside
• Using a smaller phillips bit, remove the “cage” from around the loading mechanism. You will find four screws on top, two holding on a clip on the backside and two on each side holding the plate that attaches the MD mechanism to the chassis. Below are a couple of photos to use as a reference

• Note: the screws that hold the clip on the rear of the mechanism may be longer than the rest. My unit appeared to have been worked in before so this may not be true. Please update the wiki
• Note: extra care must now be taken because the record head is no longer protected by the top cage. If you flip the mechanism over be careful not to put any sideways force on the record head as this could cause it to become misaligned.
• Flip the mechanism over and remove the two ribbon cables from the rear of the board

• Important: after the next step you must bridge a connection on the ribbon cable before removing it from its connector. Not doing this will likely damage the laser.
• Remove the screw that holds this board in place on the one said and very carefully flip it over to expose the ribbon cable for the laser. You will note two pads on the ribbon cable. These pads must be shorted before removing the cable
• Simply bridge the connection using some solder

• You can now pull out the clip retainer to release the cable and remove the cable. Set this board to the side for now
• Remove the four screws that float the mechanism on the rubber grommets

• With these four screws removed you may find the whole thing a bit awkward to handle. You must be careful of the door and it's mechanism and spring. Carefully lift this portion away from rest of the bracket paying attention to the pin that fits under the door lift as well as the remaining ribbon cables. When I did this repair I did not remove these cables but you could.
• Once you have the mechanism free you can turn it over and find the switch that needs to be replaced

• Below is a zoomed in photo. You will find at least three spots where the switch is soldered to the board. On the right side, top and bottom are two legs. On my device I found that a ground pin was soldered on the left side near the motor.
• I found it easiest to use a needle nose pliers to lift the left edge away from the motor while heating the pin on the right side of the switch. Once I had this loosened I used a toothpick under the switch to slightly pry on it while heating the connections on the other side and just kept working them until they were removed. Once the switch was removed I replaced it with the new switch. Below is a blurry photo of the switch removed

• On the switch (and the new one) you will find two guide pins that will seat into the board. Place the new switch into position with the guide pins in the holes. To complete this part, I used the toothpick to hold the switch in place and then tacked soldered the two connections on the right side, top and bottom. Once tacked into place I put a bit more solder on each connection to get a good connection. I did the same for the ground pin on the motor side of the switch.
• To the left of the switch you will find pads you can use to test the switch. They are marked gnd and chuckin. Using a mutimeter, turn on continuity mode and touch the pads. With the switch fully out it should be open, when the switch is around half way into its travel it should be closed all the way until it seats. If this does not work then check your work
• Reassemble the unit in the reverse order.
• Remember to remove the solder bridge from the ribbon cable after you put it into its socket and have closed the retaining clips
• Plug the player in and power it on. The loading mechanism will likely move around a bit and/or need you to load an MD to fully work but with a disk removed you should now see:

Congrats! You have now repaired your player and it should no longer continuously attempt to eject the disk.