Any electrical engineers out there who can help?
January 5, 2019 9:51 PM   Subscribe

Is it ok to replace a fiber optic Christmas tree power supply of input: 120V-60Hz 32W Output 12v-max 25VA with a new power supply of Input: 120v-60Hz Output 12v-max 2000ma

According to our calculations, the old power supply would have 2080ma. I am checking to make sure the new one would work. We don't want to burn down our house!

Many thanks for your expertise. Happy New Year!
posted by ragtimepiano to Technology (5 answers total)
You already figured out the right answer.

That said, if the power supply is UL rated you can be confident that if it fails it won’t do so in flames.
posted by doomsey at 10:09 PM on January 5

The new supply's power output is just 4% lower than the old one's. And that's their rated, guaranteed output. Neither will break if you overload them by a few percent; maybe their output voltage will drop a little, but that's inconsequential.

Furthermore, what's really relevant here is how much the actual light source(s) is/are drawing. That's something you usually won't find on them, nor on the box (if you still have that), but I'm sure it's not 2378mA; it's never that close to the rated supply output, if only to stay on the safe side of all production tolerances stacked up and not incur the wrath of Underwriters Laboratories. I'd estimate it to be between 1500 and 1800mA.

(I'm not an electrical engineer, but wearing my Donegan Optivisor I could be mistaken for one)
posted by Stoneshop at 3:31 AM on January 6 [2 favorites]

The fact that the old supply is rated in VA instead of Watts suggests it's a AC-AC supply. Make sure it's not before replacing it with a AC-DC supply.
posted by Grumpy old geek at 11:15 AM on January 6 [2 favorites]

Dear grumpy old Geek, the old Supply reads
" AC adaptor".
What would the problems be with just an AC adaptor so that we can't replace it with an AC DC? Thanks in advance
posted by ragtimepiano at 12:40 PM on January 7

Never mind, we checked and the new adapter is indeed AC-AC.
posted by ragtimepiano at 11:05 AM on January 9

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