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Old 09-22-2022, 11:29 AM   #1
EasyGoing1
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Default Fish Tank LED Power Supply Gets Hot then shuts down

A good friend of mine brought to me a rather large LED light array that is used for fish tanks. IT's so large in fact, that it requires TWO ATX style power supplies.

He told me that as soon as he turns it on, the LEDs turn on, but then shortly turn off.

I tried powering the lights with just one power supply, but they wont power with just one, so with both turned on, the lights do turn on, but then they turn off.

The power supplies are identical, and one of them seems just fine, but the other one ... within 10 seconds after connecting it to power, the two heat sinks get too hot to touch... so it seems like it might be shutting itself down before it burns itself out.

Here are some pictures







I understand a little about ATX power supplies ... that there's a high side and a low side and usually a PWM chip that drive a transformer and also usually a comparator chip that keeps an eye on voltage levels etc.

Since one heat sink is on the high side and the other on the low side, its puzzling to me that both of them are getting that hot that quickly. And of course I'm not sure which fet on either heat sink is the one drawing all that current...

Advice on how to move forward here to figure this out?

Thank you,
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Old 09-22-2022, 01:23 PM   #2
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

More information about the LED is required. It's surprising to have one lamp powered by 12V or whatever directly, unless it was meant for off-grid use perhaps.

Input/hot side has transistors on them and usually there are 2 plus one for standby.
Output/safe side has all diodes on it pretty much.

Some PSUs have protection to ensure you're not drawing too much but either way, as you increase load, it will dissipate more heat - both input and output side.

I don't like high/low side because it could mean the high/low side transistor on the hot side to implement complementary drive.
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Old 09-22-2022, 01:41 PM   #3
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

12v leds or 24v leds with psu's in series?
or 5v leds?

whats the wiring??
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Old 09-22-2022, 08:24 PM   #4
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Can we see the data plate for these switching power supply

What I would do is work on the switching power supply that is having the issues of heating up very quickly but I would use some automotive head lamps as a load I would check each switching power supply individually and not together assuming that they are 12 volts each do they have a 5 volt power supply rail if so what does it power
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Old 09-24-2022, 02:44 PM   #5
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by sam_sam_sam View Post
Can we see the data plate for these switching power supply
There is no data plate. Just this label which looks rather ... homemade to me ...




Also, when I turn that power supply on WITHOUT a load connected to it ... the heat sinks of course do NOT get warm at all, but it does make this sound ... listen to all of it cause it gets more interesting about halfway through the audio.

The noise is definitely coming from somewhere in the vicinity of the heat sinks.

Also, the other power supply (the good one) does not make any noise when I power it up without a load. The chassis fan, however, does turn on.

The "bad" power supply, the one making the noise, when I turn it on without a load, the chassis fan DOES NOT turn on, though I seem to remember it did turn on when it was under load though I can't be 100% certain on that.

Quote:
Originally Posted by sam_sam_sam View Post
What I would do is work on the switching power supply that is having the issues of heating up very quickly but I would use some automotive head lamps as a load I would check each switching power supply individually and not together assuming that they are 12 volts each do they have a 5 volt power supply rail if so what does it power
Here are some more pics of the unit itself and the output side of the power supply. I haven't taken the circuit board out yet to start probing around. I wanted to gain some more knowledge first and get the opinion of you more experienced guys before I start taking things apart just to make sure Im proceeding in the most effective way possible.














Last edited by EasyGoing1; 09-24-2022 at 02:50 PM..
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Old Yesterday, 01:01 PM   #6
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by stj View Post
12v leds or 24v leds with psu's in series?
or 5v leds?

whats the wiring??
Quote:
Originally Posted by eccerr0r View Post
More information about the LED is required.
See my most recent post.
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Old Yesterday, 04:26 PM   #7
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Looks like some dark looking LED’s… wonder if you got some bad ones? Test the individual string / individual LED’s with a bench PSU.
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Old Yesterday, 05:59 PM   #8
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by CapLeaker View Post
Looks like some dark looking LEDs wonder if you got some bad ones? Test the individual string / individual LEDs with a bench PSU.
Well I would if it weren't for this power supply that isn't working properly... 10 seconds after turning it on the heat sinks are too hot to touch. Yet the other power supplies heat sinks ae cool to the touch. Not to mention the noise the PS is making which I posted the audio here yesterday.
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Old Yesterday, 06:30 PM   #9
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

change all the small electrolytics.
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Old Yesterday, 07:30 PM   #10
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by EasyGoing1 View Post
Well I would if it weren't for this power supply that isn't working properly... 10 seconds after turning it on the heat sinks are too hot to touch. Yet the other power supplies heat sinks ae cool to the touch. Not to mention the noise the PS is making which I posted the audio here yesterday.
What is the model number of the PSU? What IC's is it based on? I understand this light has 2 power supplies. One works good and the other one not? How are the PSU's hooked up to the 3 lights?

If I had to guess, I say the noise comes out of the big switching transformer between the two heat sinks. I would tear the PSU apart and check for cracked or dry solder joints.

Does this lamp (partially) run with only one PSU connected?
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Old Today, 06:47 AM   #11
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by stj View Post
change all the small electrolytics.
Did you listen to the sound file I posted?
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Old Today, 07:14 AM   #12
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

no, not interested.
the heat issue is first - it sounds like the driver transisters are being over-driven.
they are often driven through small blocking capacitors
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Old Today, 07:21 AM   #13
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by stj View Post
no, not interested.
the heat issue is first - it sounds like the driver transisters are being over-driven.
they are often driven through small blocking capacitors
Ive got an ESR meter ... would that not help in isolating the problem?

Also what would be causing the PS to shut off all on its own?
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Old Today, 07:45 AM   #14
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by CapLeaker View Post
What is the model number of the PSU?


Quote:
Originally Posted by CapLeaker
What IC's is it based on?
TWO ICs only





Quote:
Originally Posted by CapLeaker
I understand this light has 2 power supplies. One works good and the other one not? How are the PSU's hooked up to the 3 lights?
Through the two cords coming out of the housing each with a 4 pin round threaded connector ... reminds me of a CB Microphone connector from back in the day...




Quote:
Originally Posted by CapLeaker
If I had to guess, I say the noise comes out of the big switching transformer between the two heat sinks. I would tear the PSU apart and check for cracked or dry solder joints.

Does this lamp (partially) run with only one PSU connected?
No it does not run at all with only one power supply.
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Old Today, 08:09 AM   #15
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Look at the PCB of the PSU if there is a brand and a model number printed on it. Could be along the edge or on a not so crowded area of the PCB.
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Old Today, 08:21 AM   #16
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by stj View Post
no, not interested.
the heat issue is first - it sounds like the driver transisters are being over-driven.
they are often driven through small blocking capacitors
I took out the big caps which are printed as 680F

The meter reads one at 740F and the other as 750 F

Meter is a Fluke 17B
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Old Today, 08:27 AM   #17
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by CapLeaker View Post
Look at the PCB of the PSU if there is a brand and a model number printed on it. Could be along the edge or on a not so crowded area of the PCB.
Only identifying markings on the PCB are these

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Old Today, 08:42 AM   #18
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

still trying to come to terms with how big this thing is or isn't. I recall my small 10 gallon fish tank only needing a small lamp, then when we're talking about a 40 gallon tank, a single F40T12 would be sufficient to illuminate it.

Then there are LEDs now, those LEDs, 25 of them per set, so there's 75 of them total. If they were 1W a piece, 75 watts, that's a very bright lamp... but a single ATX-sized power supply should be more than sufficient.

If they were 3W a piece, then 225W, which is REALLY bright, which a well designed single ATX-sized power supply is still sufficient, though 225W is a significant load but not unmanageable, a P4 with a GPU can get to 300W and we've had that for years.

Then comes a [email protected] power supply. I suppose that's inrush...but that's 720W...

hmm...
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Old Today, 08:52 AM   #19
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

Quote:
Originally Posted by eccerr0r View Post
still trying to come to terms with how big this thing is or isn't. I recall my small 10 gallon fish tank only needing a small lamp, then when we're talking about a 40 gallon tank, a single F40T12 would be sufficient to illuminate it.

Then there are LEDs now, those LEDs, 25 of them per set, so there's 75 of them total. If they were 1W a piece, 75 watts, that's a very bright lamp... but a single ATX-sized power supply should be more than sufficient.

If they were 3W a piece, then 225W, which is REALLY bright, which a well designed single ATX-sized power supply is still sufficient, though 225W is a significant load but not unmanageable, a P4 with a GPU can get to 300W and we've had that for years.

Then comes a [email protected] power supply. I suppose that's inrush...but that's 720W...

hmm...
So I learned a little about the company that designed these ... apparently they were quite the item back in the mid 2000's but another company ... some aerospace company had gotten a patent on marine aquarium lighting that I guess was close enough to this exact lighting system that they sued the company and put them out of business. The company, PFO - had been making and selling these LED lighting units long before this other company was awarded a patent.

Its a shame ... They apparently had a good reputation as a company of quality and customer service.

Also, when these lights turn on briefly, they are different colors and they are not very bright
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Old Today, 09:20 AM   #20
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Default Re: Fish Tank LED Power Supply Gets Hot then shuts down

So since the two big caps are reading at around 750F when they are supposed to be 680F ... are they bad?
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