Hi All,
Please listen to the recorded mp3 file : I play a pure sine wave (852Hz) . As I turn the level up, an strange noise apears. I have no clue where the problem is. My monitor is SC307 which uses SMPS , DSP and Class D amplification. Any help would be appreciated
Please listen to the recorded mp3 file : I play a pure sine wave (852Hz) . As I turn the level up, an strange noise apears. I have no clue where the problem is. My monitor is SC307 which uses SMPS , DSP and Class D amplification. Any help would be appreciated
I did some voltage measurments:
At low levels:
VA+ = 31.32v
+VB = 21.36
-VB = -21.30
Voltage for 7812's input : 16.61v
At high levels(which noise apears):
VA+ = 28.48
+VB = 29.95
-VB = -29.75
Voltage for 7812's input : 16.43v
Is that normal ?VB voltages increases as the level gets higher. (or maybe secondary rectifier fast diodes are damaged)
At low levels:
VA+ = 31.32v
+VB = 21.36
-VB = -21.30
Voltage for 7812's input : 16.61v
At high levels(which noise apears):
VA+ = 28.48
+VB = 29.95
-VB = -29.75
Voltage for 7812's input : 16.43v
Is that normal ?VB voltages increases as the level gets higher. (or maybe secondary rectifier fast diodes are damaged)
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The primary side of the switching transformer is common for all the secondary voltages ! So I decide to replace the rectifier diodes. I think they are lazy. As I drive more signal, the amp section draws more current , and the PS tries to supply that by increasing the pulse width which is a good thing for lazy diodes😄
- I don't have an scope.
- I don't have an scope.
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This is just lottery way of repair. Sorry, only guesswork and essential tools missing. You will most certainly fail.
I changed the diodes. Not only the problem didn't get solved, also a hum noise added😂 which is increase or decrease by volume knob.
