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RE: Zerozone 100VA PSU Fuse Issue

Duster,

The X1 DVR CATV box is drawing less than 1/2 the available power the power supply is built to supply. (12Vdc X 3 amps = 36 watts) The power supply is rated for 6 amps at 12Vdc. (6 X 12 = 72 watts)I doubt the CATV box draws 3 amps. 80% of 3 amps at best, jmo.

I personally would not increase the size of the AC line fuse from 1.6 amp.

If the 1.6 amp fuse has blown twice, and you are 100% sure it is not X1 Cable Box causing the overload,then there is a problem with the power supply.
Maybe the full wave bridge rectifier, or an electrolytic cap, or maybe a voltage regulator, or maybe an intermittent short. Something is drawing power in the power supply it normally should not. The 1.6 amp AC line fuse is doing what is is intended to do. First protect the power transformer from drawing more current than the wire of the two windings can safety handle. If the windings are overloaded beyond what the wire in the windings is rated for you will burn it up. The 1.6 amp AC line fuse is already twice the rating of the FLA rating of the transformer. (I see a label on the transformer, does it give any rating specs?)

Second, if the designer of the power supply, designed the DC power supply properly, it should handle an overload caused by a connected load until the AC line blows. And hopefully if a component is the DC power supply causes an overload. Hopefully!

It still puzzles me, somewhat, why the Line fuse is sized at 200%, twice, the FLA rating of the primary of the transformer and not instead the FLA rating of the DC power supply. (The transformer will deliver more power than the DC power supply is designed to deliver)

EDIT:
Clarification.
There is nothing wrong with oversizing the power transformer.
The designer may have sized the transformer so it would not be loaded more than 80% of its' rating.
He may have, and I would not be surprised, sized the max output rating of 6 amps current, at 12Vdc, at 80% of the actually FLA continuous duty output rating.




Edits: 07/24/17 07/24/17
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