Inspection found that the machine switch breakdown, pipe and pulse width adjustment have been substitution. Q901 used 2 sc1942, presently D820 instead, close to the parameters, can be substitution; Pulse width adjusting pipe Q903 used 2 sc2060, now with 3 dg130a substitution, access to relevant data, two pipe pressure were similar, but the 3 sc2060 dg130a ICM parameter is less than 2. Estimate the reason is the improper tube substitution repeated loss switch tube, with a quality goods after 2 sc2060 replacement, switch tube damage, no longer troubleshooting. 8hmservice manual download site
 8hmservice manual download site
 8hmservice manual download site
Q903 work in the state of low voltage in the switching power supply, therefore asked the low saturation voltage, high magnification, good frequency characteristic, to ensure that the sensitive and effective control. Repair personnel before choosing the substitution of tube did not meet the above requirements, the switch tube is often broken down. 8hmservice manual download site
According to the maintenance practice of repeated loss power switch tube, analysis, summed up the following experience for reference. 8hmservice manual download site
1. The switch tube is the cause of damage associated with each other, classification is relative. Over-current, loss was damaged in the voltage breakdown performance, a loss is a symptom of the switch tube current is added, etc., maintenance judgment should be balanced. 8hmservice manual download site
2. The fault characteristics of the switch tube damage and the damage reason to roughly the following: 8hmservice manual download site
(1) rush absorbing circuit breakdown switch tube failure only, won't hurt load, replace + B after basic constant voltage; 8hmservice manual download site
(2) voltage and pulse width adjusting circuit failure, breakdown switch tube, and can damage the load circuit elements such as pipe, the abnormal voltage + B; 8hmservice manual download site
(3) flow was damaged, the switch tube temperature rise, + B voltage drop; 8hmservice manual download site
(4) filter capacitor fails, grating and image with transverse dark belt or moire, + B voltage drop. 8hmservice manual download site
3. The repeated loss switch tube failure in overhaul, to avoid element damage, reduce loss, can take the following measures:

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