Fault phenomenon: customer repair a computer active speakers, poor quality, customer self fault is by power transformer primary winding burn caused by, original transformer secondary voltage is 9V, due to not buy 9V, so with the same volume of 12V transformer substitution, the small volume state good sound quality, medium volume sound quality hair broken ugly, so repair.CBrservice manual download site
Analysis of the maintenance: disassemble the observed power amplifier board on chip with three tea2025, BTL circuit applications, respectively, to drive a subwoofer and two satellite box speakers. The voltage of the small volume is 10V, the medium volume voltage is 5V, the music gap voltage is 13V, which is the typical supply current shortage phenomenon.. Power transformer for the power transformer is observed, and the wire diameter of the secondary winding is very thin, and the original transformer is the secondary winding diameter of the secondary winding, and the new transformer is inferior quality.. Original transformer tags show secondary voltage of 9V, current 1.35a, pick a secondary voltage of 9V, current 1.3A transformer substitution test, regardless of the volume of small and medium volume, high volume state quality are very good measured volume state voltage 10V small fluctuations in is normal, troubleshooting.CBrservice manual download site
While measuring the customers to buy the primary winding of the transformer DC resistance to 550 K, the substitution of the primary winding of the transformer DC resistance for 120 ohms, from two primary winding of the transformer DC resistance measurement results can be seen customers to buy the transformer although substitution transformer volume and size, but is the primary and secondary winding wire diameter is Jerry, estimate the quality of the core is not very good, the natural output power is greatly reduced and the flooding of the inferior quality of the transformer market purchase easily fooled, its characteristics is no-load measurement of secondary voltage goushu, once installed using the changing load current high secondary voltage of a serious decline. It is proved that the direct current resistance of primary winding and the wire diameter of the secondary windings are simple to judge the quality of the transformer..

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