And the machine appear dull and silent, a "squeak" cries, + B or power supply load has a short circuit protection circuit. DPYservice manual download site
+ B power load short circuit, the main line is the output load short circuit, the second is the audio power amplifier load short circuit. DPYservice manual download site
 DPYservice manual download site
Action is to protect circuit. The fault (1) the switch power supply, high output voltage + B, line flyback pulse will increase, make the protection circuit starts. (2) a line flyback high capacitance makes flyback pulse open, protection circuit starts. (3) the output pipe line current is too large, the protection circuit. (4) fault protection circuit itself makes it false action. Such as 0751 short circuit, and poor CP751, etc. Specific inspection is as follows: DPYservice manual download site
(1) boot C909 measurement on both ends of the voltage of 0 v. Disconnect thyristor series resistance after R751 C909 measurement on both ends of the voltage is more than + 111 v, quickly cut off power supply, or r will damage to other components. DPYservice manual download site
(2) check the regulated power supply, sampling circuit D907, C901 are good. Tested according to the original film block IC901 online foot resistance, no obvious abnormalities. Remove the diaphragm, the positive and negative to the resistance test (3), (4) feet are 121 k Ω, description on the thick diaphragm regulator tube has been open, so losing adjustment function, make + B higher voltage, protection circuit.DPYservice manual download site