I hope this is the right place to post this, since it deals with the tuner section of a receiver. I have an NAD 705 I've owned since new. The amplifier part still works fine, and it plays all sources except the tuner perfectly, good audio quality, all switches and dials and display works. What happens with the tuner is this: pressing the tuning up and down buttons cause the displayed frequency to go up and down appropriately, but the tuner audio bears no relationship to what frequency is displayed. On power-up, the tuner starts at 87.5Mhz or so, and increses over the course of about 30 seconds up to 108 Mhz (you can tell by what station it is receiving -- the display doesn't change) and then stops. The audio quality is good when it has a station tuned in, but of course it tunes past every station except the highest one pretty quickly. All the presets have 197.0 Mhz stored in them and you cannot change the value by storing a new one. Changing the mode from search or tune to preset causes the speakers to turn off. So that's what's happening from a symptoms point of view. I have the schematic and service manual, but there's no theory of operation and I am a bit at a loss how to proceed in debugging this. I am guessing at some point that a digital value is converted to a voltage that is fed to the analog tuner. I have access to a bunch of test equipment, including a meter and scope (and even a logic analyzer) and I know how to use them, but I have no documentation on the digital part of the circuit beyond the schematic and don't know where to begin. My gut from fixing a lot of 70's stereo receivers is that when something just dies, the most likely culprit is in the power supply, so my first thought is check the voltages going from the PS into the tuner board. Thanks!