Hello,
I'm looking at a power supply board from a Harman Kardon MAS101 amp, because it's fun, basically. The problem is I'm pretty crap at looking at a circuit and understanding what it does. I've tried to make a faithful drawing of the relevant parts though.
I'm hoping someone can lend me their intuition to explain how the 5.6V standby pin gets its voltage in the diagram attached.
A few notes:
- I'm not very good at identifying the type of transistor or their pinouts in-circuit, so I represented them as three pin rectangle/capsule shapes, but hope the context is enough to understand it anyway.
- Also I've probably misrepresented the internal topology of transformers. Don't know a lot about it.
- The output pins are the circled voltages. The 5.6vsb is measuring -0.4V, which I assume is bad. The logic board seems to boot when I apply 5V to its 5.6VSB pin so I'm assuming that this is where I should focus if I want to understand how to eventually revive the thing.
Some measurements (logic board etc is unplugged):
+16: -6.99 and dropping
+15: sometimes +15-16V, sometimes < 10V, after plugging it in
-15: -14.65, stable
+5.6V_STB: -0.41 V, stable
+35V & -35V: 0 V
I'm looking at a power supply board from a Harman Kardon MAS101 amp, because it's fun, basically. The problem is I'm pretty crap at looking at a circuit and understanding what it does. I've tried to make a faithful drawing of the relevant parts though.
I'm hoping someone can lend me their intuition to explain how the 5.6V standby pin gets its voltage in the diagram attached.
A few notes:
- I'm not very good at identifying the type of transistor or their pinouts in-circuit, so I represented them as three pin rectangle/capsule shapes, but hope the context is enough to understand it anyway.
- Also I've probably misrepresented the internal topology of transformers. Don't know a lot about it.
- The output pins are the circled voltages. The 5.6vsb is measuring -0.4V, which I assume is bad. The logic board seems to boot when I apply 5V to its 5.6VSB pin so I'm assuming that this is where I should focus if I want to understand how to eventually revive the thing.
Some measurements (logic board etc is unplugged):
+16: -6.99 and dropping
+15: sometimes +15-16V, sometimes < 10V, after plugging it in
-15: -14.65, stable
+5.6V_STB: -0.41 V, stable
+35V & -35V: 0 V
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