DENON Input selector jumps randomly

To switch your Onkyo PA 7SD amplifier to the auxiliary (AUX) input, follow these steps:

1. Locate the input selector: Look for the input selector knob or button on the front panel of the amplifier. It is usually labeled with various input options such as "AUX," "CD," "Tuner," etc.
2. Turn on the amplifier: Ensure that the amplifier is turned on by pressing the power button or flipping the power switch.
3. Select the AUX input: Rotate the input selector knob or press the corresponding input button to choose the AUX input. The label "AUX" should be indicated on the display or selector knob.
4. Connect your device: Connect the audio output of your desired device (e.g., smartphone, MP3 player, or external audio source) to the AUX input on the back panel of the amplifier. Use an appropriate audio cable (e.g., RCA or 3.5mm) depending on the available input/output ports.
5. Adjust the volume: Once you have selected the AUX input, adjust the volume knob on the amplifier to your desired listening level. You should now be able to hear the audio from your connected device through the amplifier.

It is probably a problem in the control circuit. If the motor changes it shold be ok.

Hi Readers to of Fixya,
This entry is January 22, 2016.
I own a Denon PMA 735R which I bought new in 1999, it is very good Amp; starting about a few years ago the input selector would occasionally randomly jump from CD to Phono to Tape etc., but would always end up back at CD so it was not terribly annoying until a few days ago when it started happening all the time. I am a very knowledgeable electronics person (I built musical keyboards at one time) so my thought was just that it was a dust problem and I started with that premise. I fixed it using an Electrical Parts Cleaner spray and here is how I did it:
I unplugged it, removed the CD input RCA cables and removed the L & R speaker cables and took it off its shelf and set it on a towel on my soft sofa; I removed the casing by unscrewing four big silver screws on the sides (my model is silver) and the three small black screws on the back top; I removed the Input Selector indicator knob on the front and the Record Out Selector indicator knob and the Volume knob, I then removed the small nut that holds the three of them tightly in place to the front panel; I then stood it on its back so that the front was facing up; I then sprayed my Electrical Parts Cleaner spray into the Input Selector indicator post liberally and then put the knob back in place and kept turning the indicator back and forth for a few minutes to work the cleaner inside the post down into the circuit board connection; I did the same with the Record Out Selector indicator post and I did the same with the Volume post; I then put the small nuts back on the three posts and tightened them; I then put the knobs back on the three posts; I then stood it back on its normal upright position and put the casing back on and then the screws; I placed back on its shelf and hooked up the cables and switched it back on and played my CD's, it has been working perfectly fine. The whole process took less than 30 minutes.I hope this helps.

Turn table? You mean like records? lol
The output of record players is different voltage than like cd players, etc...
Does your stereo have input for turntable or are you hooking it up to an extra rca input? I had mine hooked up wrong before and it did same thing.

Sounds like you have output transistor problems. Does it have a red protection light that comes on when it shuts down? If it does it will need serviced.

Why? Are you contemplating connection of something OTHER THAN A PHONO CARTRIDGE to it?

Be advised, only a phono cartridge should be connected to a Phono input. There's more going on behind it than just voltage step-up.

bring a good contact cleaner from radio shack near you and apply spray with pipe in the selector and move it forward and backward.

try to apply a spray(contact cleaner) with long pipe to the selector and move it many times(you can get the contact cleaner from radio shack near you.

I have this same problem, and I just found that one guy over at audiokarma has posted a thorough walk-thru with pictures. (You have to register to view the pictures)
http://www.audiokarma.org/forums/showthread.php?t=218030