The mechanism of the barrier channel schematic diagram, see the picture below. The power amplifier circuit and other AV amplifier is not big difference. The only feature is to drive the tube in parallel with 2 high anti - pressure small power tubes with 5551/5401 high - pressure tubes. Two parallel paired high requirement is difficult. Paired bad midpoint voltage imbalance.XFKservice manual download site
Due to a boot on the protection. Therefore, the detection of the large power tube is firstly removed, and the B - e junction breakdown of 2SA1493 is found.. After the removal of the high power tube, the 2SC3857 / b of the 2SAl493 electrode voltage of + + 0.5V is detected, which indicates that the voltage is normal..XFKservice manual download site
Installed power tube, while monitoring the midpoint voltage regulator with side boost. The midpoint voltage stability is within 10mV.. The input audio signal CD, speakers all morning for a normal audition.XFKservice manual download site
The afternoon is directly inserted into the 220V socket, a power, just listen to the sound of "Ba". High power transistor load resistor (0.68 ohm / 3W) burn.XFKservice manual download site
Remove large power tube. The B voltage of the two tube is detected by the power: the B voltage of the Q1 is gradually reduced to O.9V by 10V. The voltage of B of 0.4V gradually decreased from 0.2V to Q0. From this, the starting on the burning pipe is due to the base voltage caused by the impact of the impact.XFKservice manual download site
Remove double push tube, starting on the Q125, Q124 B voltage from the moment 37V gradually dropped to 4.4V. The B voltage of Q132 and -40V gradually increased from the instant -6.1V to Q133. Double push tube B pole voltage transient high voltage. LED high power tube boot burn.XFKservice manual download site
Drive the base voltage of the tube from the Q120 / C Q130. B pole voltage of Q120 39.5V. 0.130 the B voltage is -39.3V. Thus determine the two tube before the normal circuit. The problem is at the level and beyond. There are two reasons for this failure: one is the insufficient pipe pressure. The performance is not stable: male one reason is the self excited oscillation (power moment).

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