NAD-T752-avr-si1 维修电路原理图.pdf

Service Information T752Circuit ChangePROBLEM: You may have a complaint about fan noise coming from theunit . The fan may also be running continuously at low volumes. See page 2*.CAUSE: When the fan speed is high , the noise is noticeable during quietpassages of music.SOLUTION: Lower the voltage to the fan by inserting a zener diode in serieswith the positive lead going to the fan. The zener diode should be 1/2wminimum and be in the range of 2.7v to 3.3v. Using a higher voltage zenerdiode than 3.3v is not recommended as it will lower the fan speed too much .This could cause overheating. See diagram 1 and 2 for reference.1. Locate two pin connector at rear of amplifier board. See diagram 1.2. Cut the pc trace that runs from the positive (red wire) line of the fanconnector to the connecting trace, as diagram 2 shows.3. Insert the zener diode as shown with the anode connected to the fanconnector pad and the cathode(black band) to the connecting trace.Diagram1 Diagram 2RadioFans.CN 收音机爱 好者资料库* Checking Idle CurrentAfter performing this or any procedure please check idle current on all fivechannels. Allow the unit to warm up for 10-15 minutes and then check theidle current. It should be approximately 1mv +- 0.25mv. High idle current 2mv ,will cause excessive heating and the fan will run continuously. Aftersetting idle current wait 25-30 minutes and check idle current again andadjust for 1mv +- 0.25mv.ChannelJumperVRFLP503R571FRP502R545CP501R522SLP801R835SRP802R836Contact:NAD Electronics International633 Granite CourtPickering, ON Canada L1K 3K1Voice: 905-831-0799 FAX 905-837-6357 RadioFans.CN 收音机爱 好者资料库