Replacement Power Supply Questions - The Planted Tank Forum
 
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post #1 of 2 (permalink) Old 01-12-2021, 06:24 AM Thread Starter
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Replacement Power Supply Questions

I have the Finnex 36" Planted plus from around 2015 and it started flashing on/off in 2017 and I recently decided to get it working again. The flashing corresponds to a clicking sound from the power supply and I know it's a common issue with the cheap power supplies that came with the unit. Ordered a new power supply from Finnex/AquaVibrant but the connector is a two prong male and so is the light so they can't plug in. Waiting to hear back from their customer service...
I've read threads about going with an aftermarket power supply light a mean well. It sounds like I have to match the DC15v output of the supply and it must produce 18w or more to power the light.

What does the switching or constant power have to do with it if anything? Will either work?

How difficult is connecting the wiring to the power supply and what does it entail? Most of the power supplies I see are open or open cages, Is this a recipe for failure if its hanging behind an aquarium? I've electrical soldered under cabinet leds, can connect wires with butt splices as well so I'm not totally inept but if it isn't something I do every day is it worth trying to go this route or am I in over my head?

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post #2 of 2 (permalink) Old 01-12-2021, 07:52 AM
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Quote:
Originally Posted by Tvadna View Post
I have the Finnex 36" Planted plus from around 2015 and it started flashing on/off in 2017 and I recently decided to get it working again. The flashing corresponds to a clicking sound from the power supply and I know it's a common issue with the cheap power supplies that came with the unit. Ordered a new power supply from Finnex/AquaVibrant but the connector is a two prong male and so is the light so they can't plug in. Waiting to hear back from their customer service...
I've read threads about going with an aftermarket power supply light a mean well. It sounds like I have to match the DC15v output of the supply and it must produce 18w or more to power the light.

What does the switching or constant power have to do with it if anything? Will either work?

How difficult is connecting the wiring to the power supply and what does it entail? Most of the power supplies I see are open or open cages, Is this a recipe for failure if its hanging behind an aquarium? I've electrical soldered under cabinet leds, can connect wires with butt splices as well so I'm not totally inept but if it isn't something I do every day is it worth trying to go this route or am I in over my head?
Nope not over your head.

First caged power supplies do need protecting but mostly just use common sense.
Second the way the led board is designed is why a) you need to match the design voltage (there is some leeway here which I will get to.) and b) voltage needs to be stable.
Switching power supplies meet both criteria in general.
Leds like the fluval are run in constant voltage mode. and are run in strings and each string usually has a terminating resistor.
The resistors function is to sort of regulate current and drop voltage.

Say you put 4 less in series that will draw 100mA at 3.5v. 4 in series..14v.
15v power supply. Add a resistor to drop voltage to 14 v.
w/out the resistors diodes see 15v or 3.75v.
The diodes now draw 200mA of current. (just play numbers) They may overheat and shorten their lifespan or may really overheat and go into thermal runaway and burn out.
Hotter the diode the lower the voltage to draw the same current and the lower the efficiency of converting electricity to photons thus again more heat.Runaway.
But now getting back to the 15v "more or less" thing.
You can get an adjustable power supply, many meanwells are tweakable on their voltage, so you can carefully increase or decrease the voltage SLIGHTLY to either squeeze more photons out or get less but cooler and longer lasting lights.


As to wiring just don't reverse positive and negative.
VOM is your friend.
Actually most of these lights are easy to disassemble and the circuit boards are usually marked so you can identify the color wire and polarity.

"A man with a watch knows what time it is. A man with two watches is never sure"
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