Volume knob only increases volume - Denon CDR-M30 CD Recorder

I had the same exact problem and I just fixed it today after finding the solution in a post from a member in a different online forum. This problem is very easy to fix on your own and does not require you to take apart the whole thing...so do not waste your money by bringing the unit in to get serviced by a "professional". All you need is some rubbing alcohol and a cotton swab. Here's the deal- Denon (and other manufacturers) uses a vasoline-like lubricant on the shaft of the volume dial so that it turns smoothly (makes sense). However, over time the lubricant can work it's way down the shaft and cause the digital volume controll switch (aka rotary encoder) to malfunction so that it's either stuck on +volume or -volume. In my case, turning the knob in either direction only caused the volume to increase to max. So here's what you do. 1. Pull the volume knob off by simply piling it straight out (easy enough) 2. Remove the tiny black plastic washer that sits at the base of the shaft housing. 3. With a clean rag, wipe off all of the grease/vasoline lubricant as best you can from the volume shaft, the tiny black washer, and inside the volume knob itself. 4. Reposition the stereo so that it is upright with the front facing the ceiling. 5. Dip the cotton swab in alcohol and thoroughly clean the volume shaft while constantly turning it back and forth. *The goal here is to work the alcohol down the shaft so it can get into the internal components which is where the rotary encoder is. By gently tugging on the dial and moving it from side to side, the alcohol should work its way into the switch and clear up the contact points- which need to be lubricant-free in order for the electronic volume control to work properly. I did this for several minutes. Then, put the volume knob back on (washer first) and let it sit for 5 minutes so the alcohol evaporates. I then plugged it in, turned it on, and the volume dial worked like a charm. Good luck!

Try spraying some electrical contact cleaner into the volume potentiometer - i.e. take off the volume knob, then spray the cleaner at the base of the plastic stalk.