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Post subject: Acoustasonic 90 Power Supply Failed
Posted: Thu Mar 22, 2018 9:13 pm
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Anyone Have Schematics for this switch mode supply?


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Post subject: Re: Acoustasonic 90 Power Supply Failed
Posted: Sat Mar 24, 2018 1:56 pm
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
I have fews Acoustasonic amp shematics , not the 90 :(


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Post subject: Re: Acoustasonic 90 Power Supply Failed
Posted: Mon Mar 26, 2018 12:03 pm
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If there are no obviously blown parts, your power supply may be going into shutdown instead of having failed.
If there is a fault in the amp such as a blown filter cap or ic, the power supply will shut down immediately.
The way to tell is to hook a scope up to the secondary of the power transformer. Do not connect to the primary side unless you have floated the AC plug on your scope. There is one ground for the primary side that is different than the secondary side. Know the difference.
At power up, you will see just a couple of switching cycles before it shuts itself down. This indicates the power supply is still ok and the problem is downstream.
If there is no switching going on, then yes, the ps is down. Using a voltmeter, check for high voltage on the main cap and the switching fet. Then check for low voltage at the control ic.
These are the toughest circuits to revive in any case. Replace all caps with identically rated parts. Pay attention to ripple current of electrolytic caps.
Good luck.


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