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In Reply to: RE: Zerozone 100VA PSU Fuse Issue posted by Duster on July 18, 2017 at 22:01:56
If as you state your load is 3A max @12V that's 36W. Not counting losses that would be 0.6A @120V. A 1.6A slow blow would seem to be adequate. Could be that there is a current surge at turn on. Those caps look big.. Have you got a schematic? Is there a small value resistor between the bridge and the first cap? Then again you could do as suggested and try a larger fuse to try to lessen the number of nuisance blows.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Good points, JKT. I think the current demand of the load might be substantially greater than 3A at times, so the best option is to simply test the fuse values between 1.6A -> 3A. It's better to blow a few fuses since I have no way of confirming the appropriate fuse rating for the application. I expect at least one of the fuse values will be sufficient, and safe for the unit to operate (knock on wood). Otherwise, it's a fine sounding linear power supply unit.
"I have no way of confirming the appropriate fuse rating for the application."
You do have the means to check the output current draw however. Since it's low voltage DC put a multi-meter, set to amps, in series with the output and turn things on. At turn-on you will probably see a momentary spike as things charge. To do a thorough check make sure all equipment downstream are discharged, letting them sit or through a bleed resistor.
The spike may not blow the supplied fuse immediately, recall you told us there were extended periods before there was trouble. it's probably at it's limit and repeated turn-on fatigues it.
I would bet a slo-blow fuse fixes your problem. I would use the fuse closest to the measured output current draw. You want to protect your audio equipment more than the power supply.
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