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Old 07-28-2012, 08:19 PM   #4
budm
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Join Date: Feb 2010
City & State: S.F. Bay area
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Line Voltage: 120V 60Hz
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Default Re: Need tips in fixing APC 1500VA UPS having buzzing noise

This UPS looks like it uses high frequency power supply inverter that is modulated with 60Hz then the high frequency gets filters out for L/C circiuts.
Basically it is AC to DC to high frequency AC modulated by 60 Hz then high frequency get filtered out to get AC since wave output. You can tell if that is the circuits being if it does not have really big transformer inside for the AC out put.
You should try to look up the spec of the original cap to see if it is non-inductive type, high pulse type, low ESR type. just match the new cap spec with the old cap spec.
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http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

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TV Factory reset codes listing:
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