Berning-TF10-pre-sch维修电路原理图.pdf

For units set up for 240 volts, a 50 ohm-10W resistor is inserted in line with the incoming mains power.CAUTION: Dangerous voltages are present inside the TF-10. Servicing should only be attempted by those experienced in working on equipment containing high voltages. A large portion of the power supply is not isolated from the power mains. An isolation transformer must be used if voltage readings are taken in these power supply areas. Power supply voltages on the secondary side of the power transformer and in the audio portions can be measured without an isolation transformer.The power supply is configured as a two-stage switcher with a buck type regulator Q1 thru Q7, follower by a power inverter Q8-Q9. If the line fuse blows after a period of time, it is possible that the regulator has failed and excessive voltage is being delivered to the audio circuits. The filament supply should be around 21 volts, if much higher the regulator has likely failed.Failure-prone parts: Q7, Q8 and Q9. D710 (replace only with fast recovery 600 volt type) When replacing power transistors be careful that they are properly seated in their sockets and the insulating bushings are aligned to prevent case to ground shorts. Audio: All 2N5461 FETs can cause excessive noise or dc offset if shorted, resulting in loud pops when switches are operated. RadioFans.CN 收音机爱 好者资料库RadioFans.CN 收音机爱 好者资料库