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Thin computer plate repair of audio power amplifier

Feb 23, 2017

Measurement, power supply output voltage at idle was normal, but +5V +12V up to 23V,-5V when you load up on -8V, and +5V have been normal. Confirmed several times damaged by a power amplifier power lead. This power supply +12V, switching impulse voltage of the transformer by D2 half-wave rectifier, C3 filter be safe voltage 12V C3 ends connected with the load resistor R2, avoid board 12V voltage at no-load but now R2 is burned open, question no load increases due to R2 open, after replacing the resistor problem still. As the no-load voltage normal, so that points of view reaction in the loop reference voltage regulator TC,TL431C, optocoupler 4N35 were normal. Check +12V rectifier circuit are normal again, one by one to view and find other words switch primary of transformer transistors and were fully normal resistive and capacitive components. Measurement +5V after filtering capacitor C1 accidents now unknown disconnect C1 hands deflection must view and return to the initial position. Practice circuit C1 in +5V load resistor R1 and L1 (100/1W) parallel, C1 two resistance values should be equal to 100 ohm the R1 yin. C1 resistance is infinite, L1 resistance to ground at both ends for 100 euro, C1 with plates welding and iron welding and power on again to load on the +5V +12V and -5V are safe and intact, the defects excluded.