NAD T743: The digital channels stop working after a short time.

Hi, have you checked the power button in the back to see if it got pressed by accident? It's a round button located right under the speaker inputs in the back.

How is TV audio (from the cable box) getting into the Receiver? If digitally, you wouldn't be missing any one channel on a connection malfunction, you'd lose them all. If analog, swap the channels around to isolate the problem (and reconsider using digital).

Check the input mode on the reciever so that they are set for dual, rather than just digital or analog. It might be set for analog and your using a digital optical in cable. Also make sure DTS mode is turned off, unless your watching a DVD that is dts enabled.

I had the same problem and finally sloved it. You have to leave the input channels ( Vid1, Vid2, SVid, Cmpt, HDMI, etc ) in the In Channel List. So push the INPUT button, go to VID1, press Menu, go down to List & Labels then check In Channel list. Do this for all the inputs and then run your Channel search again. I hope this works for you. It did for me.

This sounds like the "pre-amp" section is cutting out or there is some interruption in the signal path. A few things to try:

1) With the unit off, try "working" the volume,balance and tone controls. This means, turn them up and down a number of times to clear any debris that may be in the controls themselves.

2) Work the input selector switch the same way if it is a rotary switch.

3) Try turning on/off the tape monitor switch a few times.

4) Keep track of whether this problem is sensitive to heat. Does teh channel shut down more quickly once the unit has been on for a while?

Lastly, if you can solder, look for any solder joint that appears grainy or has rings and resolder it.

Update this with your results and we'll continue on...

Thanks,
Dan

The reciever you have has 5.1 inputs at the backof it.The only way to get Dolby True HD and DTS HD is to run the 7.1 analog out from the bd55 to the nad. You'll have to leave the 2 rear surround open on the bd55 leaving the remaining 6 connected to the nad. The digital coax and the optical will not transmit the hd data, only the analog out will. Run a hdmi right to your HD tv for picture bypassing your amp. this will workfine and you'll have the audio you want. You,ll have to change the input settings for dvd in your amp to 5.1 to recieve the audio.

To reset the the T743 hold down the video 6 and the source up buttons for 3 seconds. then power up from the back button

NAD Technical Bulletin T743-H2005-06 describes the problem "Unit may shut down, shortly after turn on".  Reason: There is a diode on the standby board that maybe operating intermittently.  Solution: Locate and identify D756 on the standby board.  Change only if the diode is a 1N4148.  Change from a 1N4148 to a 1N4004 or equivalent.  
It is located near a transformer and some fuses.

I have had the front, left and right channels go out over time. I have fixed all of them, and each time it has turned out to be a cold solder joint. While I love NAD and will continue to purchase there equipment, this generation is plagued with poor workmanship.

To fix the channel going out, I removed the top cover. Back cover and 2nd card from the left (looking at the receiver from the back side). This card handles all of the audio processing. I have found cold solder joints all over this board which has caused channels to suddenly go quite. I have never found a bad component. Also, I have cleaned the interconnect to be backplane (board that the audio processing board connects to) in the case of the center channel going quite.

If you have poor FM reception, the first board from the left (looking at the receiver from the back side) may have a cold solder joint on the coaxial connection for the FM antenna.

I have had the T743 for about three years now. The first unit which I got from the local shop was doing exactily like your described after couple of minutes use. Well, I took is back and got a new one covered by the warranty.

Unfortunately I never got any explanation to this problem from my local shop or anywhere else, so I guess the only way is to contact your local shop.