# Dead LED power supply Critique of design wanted

#### jeffkrol

Joined Dec 8, 2015
13
An acquaintance of mine had an aquarium light that the power brick failed.
Here's the gory pics..
What do you think?

#### wayneh

Joined Sep 9, 2010
16,384
I don’t repair these anymore. Shop around and you can probably get one with higher capacity for under $10. Thread Starter #### jeffkrol Joined Dec 8, 2015 13 I don’t repair these anymore. Shop around and you can probably get one with higher capacity for under$10.
Sorry, was looking for a critique of the overall design..Thing smoked pretty bad and the diode rectifier had de-soldered itself..
No fuse on the ac side.

Rated 36V 4A out.

#### #12

Joined Nov 30, 2010
18,210
It's impossible to critique a design with no schematic and no specs for any part whatsoever.

That said, the fact that the rectifier unsoldered itself is an indicator of an inexperienced designer at the circuit board level. I've seen a lot of cracked and unsoldered joints in 50 years and it's always related to heat. In the 1970's it was 2 watt resistors on TV and radio circuit boards. In the 2000's I saw unsoldered compressor relays on circuit boards in refrigerators. I have resistors rated at 2 watts and they are nearly as large as 1 watt resistors. That only means the resistor can survive at a higher temperature than they used to. What it doesn't mean is, "Circuit boards dissipate heat twice as well as they did 50 years ago."

Give a beginner a design program and they will believe it like it was handed down by Moses because they don't have any wisdom that comes with experience. Either that or the penny pinchers are telling them not to think because it costs money to guard against a heat problem that isn't going to fail within the warranty period.

#### ci139

Joined Jul 11, 2016
1,368
if the primary of the flyback transformer developes short turns ... say because of 24/7 operation and insufficient cooling -or- continuous - a bit above normal - mains voltage or the aging (secondary side) filter capacitor - the feedback loop is cut and the thing destroys itself in a flash .. . . there might be other failure mechanisms

i had 2x 12V 1A led supplies - 1-st failed in less than a year (it had a glued together fractured ferrite core ???) - the second one still works

#### MisterBill2

Joined Jan 23, 2018
5,796
An acquaintance of mine had an aquarium light that the power brick failed.
Here's the gory pics..
What do you think?

OK, a critique of the device is that it does have an input filter but not an adequate one, and it looks like it may have a MOV to protect from line spikes, but if that small tan block next to the yellow block capacitor is not a fuse then it is not protected. Most of the control circuitry is surface mount on the underside of the board and so it can't be seen. If you have the specifications you can get another supply and be back lighting the LEDs.

#### ci139

Joined Jul 11, 2016
1,368
the input filter is the
covered by the white foam (on the picture above-right next to the yellow lo ESR cap)