My Samsung HT-DM550 shows "lock"

Most likely, your unit has a condition known as DC Offset, meaning you have a bad amplifier. For more information, please visit my website at audioserviceclinic.com. Thank you.

Hello!

I'm adding a link to the "troubleshooting" part of the manual. Hopefully, it will help! Other information Samsung HT C5500 63 68

The operation manual is available for free download from Samsung at this site: http://downloadcenter.samsung.com/content/UM/200305/20030529145700437_MW5592.pdf
The answer to how to lock and unlock is on page 15 of the manual. It's instructions are: 1. Press the '0' button, the display will show: "PRESS 1- DEMO 2-CHILD LOCK"
2. Press the "2" button, the display will show: "PRESS START"
3. Press the start button and the display will show "LOCK" then returns to the time of day.
At this point the microwave can't be used. To unlock, just repeat steps 1-3.
Hope this helps

Do you have any multichannel digital inputs connected?

http://www.retrevo.com/support/Samsung-HT-AS720-Home-Theater-Systems-manual/id/6333ci454/t/2/

REPLACE THE LASER

Samsung Home Theater Systems have a Dealer Lock or Tray Lock Function that prevents the disc tray from being opened.
There are four procedures for turning off the Dealer Lock function. Try one, then the other, to see which works on your system.
Unlocking Procedure 1 To turn off the Dealer Lock function, follow these steps:

1. Turn on your Home Theater System.
2. Press the Stop button on the front panel and the Power button on the remote control simultaneously for four seconds.

Note: Repeating the two steps above turns the dealer lock on again.
Unlocking Procedure 2 To turn off the Dealer Lock function, follow these steps

1. Turn on your Home Theater System.
2. Press and hold the Function button on the front panel for 3 seconds. The display shows the word Unlock.

Note: Repeating the two steps above turns the dealer lock on again.
Unlocking Procedure 3 To turn off the Dealer Lock function, follow these steps

1. Turn on your Home Theater System.
2. Press and hold the Open/Close button on the DVD player on the front panel for more than 4 seconds.

Note: Repeating the two steps above turns Dealer Lock on again.
Unlocking Procedure 4 To turn off the Dealer Lock function, follow these steps

1. Using the HTS remote press the Menu button + 712, and the HTS will display CAN OPEN.

The Dealer Lock feature is mainly used by retailers to ensure that the display discs are not removed. However, parents of young children may find this feature very useful as well.

Samsung Home Theater Systems have a Dealer Lock or Tray Lock Function that prevents the disc tray from being opened.
There are four procedures for turning off the Dealer Lock function. Try one, then the other, to see which works on your system.
Unlocking Procedure 1 To turn off the Dealer Lock function, follow these steps:

1. Turn on your Home Theater System.
2. Press the Stop button on the front panel and the Power button on the remote control simultaneously for four seconds.

Note: Repeating the two steps above turns the dealer lock on again.
Unlocking Procedure 2 To turn off the Dealer Lock function, follow these steps

1. Turn on your Home Theater System.
2. Press and hold the Function button on the front panel for 3 seconds. The display shows the word Unlock.

Note: Repeating the two steps above turns the dealer lock on again.
Unlocking Procedure 3 To turn off the Dealer Lock function, follow these steps

1. Turn on your Home Theater System.
2. Press and hold the Open/Close button on the DVD player on the front panel for more than 4 seconds.

Note: Repeating the two steps above turns Dealer Lock on again.
Unlocking Procedure 4 To turn off the Dealer Lock function, follow these steps

1. Using the HTS remote press the Menu button + 712, and the HTS will display CAN OPEN.

The Dealer Lock feature is mainly used by retailers to ensure that the display discs are not removed. However, parents of young children may find this feature very useful as well.

check the dust content on in the m,achine then check your settings to make sure its adjust accordingly

This is a problem with the lens..
Get a lens cleaner CD with liquid and clean your DVD drive(just put two drops of liquid on CD and press play)
If this doesn't work you will need to replace the lens...The repair cost is not very high for replacing lens..

following is pasted from SV-7000W manual: 1 To lock the VCR, hold down the P/STILL (II) button for approximately five seconds. Result: The lock indicator (LOCK) is displayed. If a cassette is in the VCR when you lock it, the cassette will first be ejected. 2 To unlock the VCR, hold down the P/STILL (II) button again for approximately five seconds. Result: The lock indicator (LOCK) is no longer displayed. If that fails, try the same thing using the play/stop button. Cheers