Here we go again with another PSU!
Because of the last two successful repairs a friend of mine brought his Enermax Revolution87+ 850W power supply. He complains that his PSU emits an annoying whining when using the PC in idle.
Actually it's true, it's really annoying and disappears on higher loads (for instance when running a game). On idle, this whine is louder whenever I do something (e.g. move the cursor or a graphic element, such as the scroll bar on a web page). I assume that, since output voltages are constant, the whine is definetely caused by a change of current (supplied when doing something indeed).
Because of this, I must think the issue is caused by an inductive element in the PSU. Starting from that, I tried to find the culprit using the straw method, but couldn't really understand where it comes from. So, I reversed the schematics involving the inductors and transformers present on the secondary side. The schematics is attached below. Pictures of the power supply can be found here.
The switching controller, a CM6901, works at 125kHz on the test setup (a motherboard+cpu, without ram, so looping in POST) and a variation of the controller's internal oscillator frequency causes a louder and different whine. The whine definetely comes from one (or both?) of the two transformers T1 or T2, or maybe from the inductor L1.
What should I do to clearly understand which one of these emits the whine? If it's a transformer, what can I do to fix it?
Because of the last two successful repairs a friend of mine brought his Enermax Revolution87+ 850W power supply. He complains that his PSU emits an annoying whining when using the PC in idle.
Actually it's true, it's really annoying and disappears on higher loads (for instance when running a game). On idle, this whine is louder whenever I do something (e.g. move the cursor or a graphic element, such as the scroll bar on a web page). I assume that, since output voltages are constant, the whine is definetely caused by a change of current (supplied when doing something indeed).
Because of this, I must think the issue is caused by an inductive element in the PSU. Starting from that, I tried to find the culprit using the straw method, but couldn't really understand where it comes from. So, I reversed the schematics involving the inductors and transformers present on the secondary side. The schematics is attached below. Pictures of the power supply can be found here.
The switching controller, a CM6901, works at 125kHz on the test setup (a motherboard+cpu, without ram, so looping in POST) and a variation of the controller's internal oscillator frequency causes a louder and different whine. The whine definetely comes from one (or both?) of the two transformers T1 or T2, or maybe from the inductor L1.
What should I do to clearly understand which one of these emits the whine? If it's a transformer, what can I do to fix it?
