I bought a sony disc explorer 400 dvd used. When I plug it in and turn it on the tray just keeps rotating back and forth. None of the buttons work when it's doing this. Does someone have a solution?

The error code C 31 00 on Sony DVD Home Theater System usually indicates a mechanical issue with the disc changer mechanism. Here are some steps you can try to resolve the issue:

1. Turn off the power to the DVD Home Theater System and unplug it from the wall outlet.
2. Wait for a few minutes, then plug the system back in and turn it on.
3. Press the "Eject" button on the remote or the unit to try to eject the disc tray.
4. Gently try to move the disc tray by hand to see if it is stuck or obstructed.
5. If the disc tray does not move, or if you hear any unusual noises, it may indicate a more serious mechanical issue that requires repair.

If none of these steps resolves the issue, it's recommended to contact Sony customer support or a qualified technician for further assistance.

No there will not be a easy fix for this. You can keep putting up with this the way you have been or buy a new receiver and try to sell this one on craigslist, eBay, etc.

Works with most Sony Players

Step 1
Unplug the power cord of the Sony Blu-ray player. Plug the power cord back in. Turn on the Sony Blu-ray player. Turn on the TV to which the Sony Blu-ray player is attached. Wait for the "No Disc" text to appear on the front of the Sony's LCD display and on the TV's screen.

Step 2
Press the "Eject" button on the remote control. Wait for the disc tray to eject itself from the front of the Sony Blu-ray player.

Step 3
Press the "Disc Info" button on the remote control. Look for a number to appear on one of the upper corners of the screen of the TV.

Step 4
Press the "Disc Info" button repeatedly until the number "9" appears on the TV's screen. This number indicates that the Sony Blu-ray player is now set for "multi-region" and will play any Blu-ray disc that is commercially made.

Step 5
Turn the Sony Blu-ray player off using the remote control. Turn the Sony Blu-ray player back on using the remote control. Press the "Eject" button on the remote control to close the disc tray. Turn the Sony Blu-ray player off using the remote control.

From www.sony.com

Unable to eject a disc.Solution

Follow the steps below to troubleshoot this issue.

IMPORTANT: If model-specific information is required to complete any of the steps in this solution, refer to the operating instructions supplied with the product. Manuals are available online through the Manuals/Specs/Warranty link on this page.

1. Ensure the child lock feature is disabled.
2. Attempt to open the disc tray.
3. If the issue is not resolved, turn off the DVD player.
4. Unplug the power cord from the electrical outlet for 30 seconds.
5. Plug the power cord back into the electrical outlet.
6. Attempt to open the disc tray.
7. If the disc tray still does not open, simultaneously press the POWER + STOP + EJECT buttons.
8. If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons.

   NOTE: This step may not apply to all models.DISC1 is not available on all DVD players.
   

Must used a philip screw driver take out all the screws to the dvd player.Must take the DVD player aparts.Take aparts out the dvd player guard shield to the dvd drive to take out the dvd dic or dics out.Don't push the open button any more,the disc or discs is jamming ur dvd door tray.Will burn out ur disc tray motor,if u keep trying push the open button,trying opening it that way.

Ensure the child lock feature is disabled. Attempt to open the disc tray. If the issue is not resolved, turn off the DVD player. Unplug the power cord from the electrical outlet for 30 seconds. Plug the power cord back into the electrical outlet. Attempt to open the disc tray. If the disc tray still does not open, simultaneously press the POWER + STOP + EJECT buttons.
If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons or the RETURN + ENTER+ POWER buttons.
If the issue is still unresolved, service may be required. The Sony eService Web site at http://eservice.sony.com/ can assist you in obtaining service from a Sony Service Center or locating a Sony Authorized Servicer.

Ensure the child lock feature is disabled. Attempt to open the disc tray. If the issue is not resolved, turn off the DVD player. Unplug the power cord from the electrical outlet for 30 seconds. Plug the power cord back into the electrical outlet. Attempt to open the disc tray. If the disc tray still does not open, simultaneously press the POWER + STOP + EJECT buttons. If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons or the RETURN + ENTER+ POWER buttons. If the issue is still unresolved, service may be required. The Sony eService Web site at http://eservice.sony.com/ can assist you in obtaining service from a Sony Service Center or locating a Sony Authorized Servicer.

Ensure the child lock feature is disabled. Attempt to open the disc tray. If the issue is not resolved, turn off the DVD player. Unplug the power cord from the electrical outlet for 30 seconds. Plug the power cord back into the electrical outlet. Attempt to open the disc tray. If the disc tray still does not open, simultaneously press the POWER + STOP + EJECT buttons. If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons or the RETURN + ENTER+ POWER buttons. If the issue is still unresolved, service may be required. The Sony eService Web site at http://eservice.sony.com/ can assist you in obtaining service from a Sony Service Center or locating a Sony Authorized Servicer.

To get to the menu with region type need to push stop twice and you get Check menu with:
0.Quit
1.All
2.Version
3.Peripherial
4.Servo
5.Supply
6.AV Decoder
7. Video
8.Audio

Push 2 and you get to the next menu
0.quit
1. All
2.Revision
3.Rum check Sum
4. Model type
5. Region
6. M't Check

In order to open the disc tray.apply one of the following solutions;
--- Turn off the DVD player. Unplug the power cord from the AC outlet for 30 seconds.
Plug the power cord back into the AC outlet. Try to open the disc tray.
--- If the disc tray still does not open, simultaneously press the POWER + STOP + EJECT buttons.
--- If the disc tray still does not open, simultaneously press the DISC1 + STOP + EJECT buttons ,
--- If the disc tray still does not open simultaneously press the RETURN + ENTER+ POWER buttons.
If the problem is still unresolved, a service may be required.
good luck...