A Taiwan XF-SR-1000T Chang statements smart voice AIDS system not work, fault phenomenon is plug Shang power Hou red indicates lamp bright, by "power" key red into green, but with electronic pen scan textbook Shi is silent, press machine Shang of "match" key Shi also no any voice (the key for electronic pen and machine of match, normal situation Xia by Xia Hou will issued "is match" of voice) preliminary suspected sound put most appeared fault.

Carefully open the machine, found mainly consists of switching power supply and the motherboard of the machine consists of two parts, including switching power supply output for 20V/2A. Soft package processing chips on the motherboard. Other chips are: TL2575-5, 2.4GRF, switch power supply transponder CC2500 and electronic volume control PT2257 a s, class-d audio amplifier and preamplifier PT2308-S TPA3123D2.

By first measuring the supply voltage of 36V is abnormal, would like to fix the power supply look for other failures, then remove the power box opens, for ease of maintenance given role in its schematic diagram (see attached map).

Power working principle is: +300V after the rectifier voltage by R5, R6 to the PWM chip IC1 (AAEQC) ⑤ feet, four foot controlled PWM pulse signal output via the Q3 (C1815) and Q4 (A733) amplified through R10 IRFIB5N65A and D3 to field effect transistor (Q1) grid. Q1 keeps switching on will have a corresponding output voltage in the secondary sensor, after twin diode C9281 (D4) rectifier and C6, C7, C12, L2 filtering circuit evacuation to the motherboard. R13, R15, R16, VR1 and voltage sampling circuit that includes the U3, P521 (lC2) coupled to send error signal to IC1 the 20V output voltage of ② feet to keep the machine unchanged. R4 is the Q1 source flow sampling resistor R9 to IC1 black feet to protect 01 from damage due to excessive current.

Output voltage does not change when you adjust VR1 (due to power supply with an output voltage), based on experience, judgment should be the voltage regulator problems. Investigation of R13, R15, R16 and VR1 is no problem. Ready to try optocoupler P521 and substitution A2431 contemporary A2431 measured output voltage is 19V, fine tuning stable output voltage of 20V unchanged after VR1, power appears to have been fixed.