NAD-T752-avr-cc1 电路图 维修手册.pdf

Service Information T752 Circuit Change PROBLEM: You may have a complaint about fan noise coming from the unit . 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 quiet passages of music. SOLUTION: Lower the voltage to the fan by inserting a zener diode in series with the positive lead going to the fan. The zener diode should be 1/2w minimum and be in the range of 2.7v to 3.3v. Using a higher voltage zener diode 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 fan connector to the connecting trace, as diagram 2 shows. 3. Insert the zener diode as shown with the anode connected to the fan connector pad and the cathode(black band) to the connecting trace. Diagram1 Diagram 2 RadioFans.CN 收音机爱 好者资料库 * Checking Idle Current After performing this or any procedure please check idle current on all five channels. Allow the unit to warm up for 10-15 minutes and then check the idle current. It should be approximately 1mv +- 0.25mv. High idle current 2mv ,will cause excessive heating and the fan will run continuously. After setting idle current wait 25-30 minutes and check idle current again and adjust for 1mv +- 0.25mv. ChannelJumperVR FLP503R571 FRP502R545 CP501R522 SLP801R835 SRP802R836 Contact: NAD Electronics International 633 Granite Court Pickering, ON Canada L1K 3K1 Voice: 905-831-0799 FAX 905-837-6357 RadioFans.CN 收音机爱 好者资料库