This kind of fault occur in power input circuit and + 5 v power supply circuit.
 
For this type of failure, we should first test whether TP1004 around 13 v voltage. Such as voltage of OV, general resistance R1051 is insurance, insurance tube Fl001 damage, a common cause is: switch tube QR1003 thermal breakdown, replace the same model or similar parameters of transistors; IC1001 (1) if the voltage is normal, and then test the feet about whether there is a 12 v voltage, if not, should check whether oiooi base voltage as the low level, otherwise check system control part of the circuit; If the base voltage is normal, for Ql001 bad; If IC1001 (1) the foot voltage is normal, but the machine still does not work, should detect IC1001 4. An output end (5), pet-name ruby, (13), (17) feet, sometimes due to internal IC1002 pulse power amplifier tube under the heavy load, lead to the output pipe flow is damaged, IC1002 3, 5, 7, pet-name ruby foot voltage drop. Besides replaceable IC1002, but also external transistor BU406 and 1 n4148 instead.
 
IC1001 and pick up in (23) crystals is damaged, can also cause the failure phenomenon, but is not common.