PLP-60-48 Single Output LED Power Supply - "chirping" noise

[sam_sam_sam]

Turning the SVR1 knob on the PSU made absolutely no difference to the voltage read on the CN2 outputs - it stayed at 47.8 V


What does this resistor actually do?

If I read the data sheet correctly it would adjust the current not the voltage you would have to have a load on it when you adjust the pot control

[tester001]

Turning the SVR1 knob on the PSU made absolutely no difference to the voltage read on the CN2 outputs - it stayed at 47.8 V


What does this resistor actually do?

[tester001]

It's a converter all right, but I think it may be a boost converter, not a buck converter, as the inductive coil is before the mosfet, not after.

Could be! I replaced the little board with this:

And set the adjustable power supply to output 40V with 1.5A max. The LED device sprung to life!
I ran it for a while in different modes and noted that it didn't draw more than 38W in power (as displayed at the adjustable power supply above).

Seeing the PSU itself without this little board is adjustable too, I think, the output voltage of the little board got to be out of range of the PSU itself?

I don't know. But I can confirm that the device works great when fed with 40V 1.5A max, as tested this morning.

Make a note of the PSU's output, make a mark with a waterproof pen on the blue variable resistor right next to the secondary output caps and turn it.
The voltage should go up and down. What is the voltage written on these caps on the little board?

This is an awesome idea! I can't see that it's allowed in the datasheet, but it might be. Let me try to get 40V out of it..

[CapLeaker]

It’s a converter all right, but I think it may be a boost converter, not a buck converter, as the inductive coil is before the mosfet, not after. Seeing the PSU itself without this little board is adjustable too, I think, the output voltage of the little board got to be out of range of the PSU itself?
Make a note of the PSU’s output, make a mark with a waterproof pen on the blue variable resistor right next to the secondary output caps and turn it. The voltage should go up and down. What is the voltage written on these caps on the little board?

[sam_sam_sam]

Based on the overview of the components and its placement within the device, can you tell what the little board does?





For example, if you say that the purpose of the little board is to conver 48V DC (constant current) to 40V DC (as the device specifies), I'd be tempted to replace the board with an equivalent that would bring down the voltage.

Thank you in advance.


EDIT:
I've done a bit of legwork online, and my guess is that the little board is a 48v -> 40v 60W buck converter

Thank you for posting this because now it makes sense about what this little board does if the LED light fixture actually works on 40 volts because this not a standard voltage for a switching power supply

[tester001]

Based on the overview of the components and its placement within the device, can you tell what the little board does?





For example, if you say that the purpose of the little board is to conver 48V DC (constant current) to 40V DC (as the device specifies), I'd be tempted to replace the board with an equivalent that would bring down the voltage.

Thank you in advance.


EDIT:
I've done a bit of legwork online, and my guess is that the little board is a 48v -> 40v 60W buck converter

[stj]

deleted post

[sam_sam_sam]

I was thinking the same thing about the mosfet possibly being shorted I would agree with you about that

[CapLeaker]

So you reused that same little board on the new PSU and it’s same thing what it was before? It’s the little board alright. I’d go for the MOSFET, the diode and the two large SMD caps first. If the mosfet is bad, you have to check the gate drive IC as well.

[harp]

I read your '240v is fine - only the wattage matters' as 'voltage doesn't matter'

LOL, fearless logic...

[tester001]

I would focus on this little board

I think you are right, as I have just received a replacement PSU and I get the following results with it:
PSU plugged into the mains and switched ON - no chirping
little board soldered on - chirping starts

Check the input pins ( the white pin connector) for a short if you find any thing lower than 500 ohms I would suspect I would go through the whole board

It is 290 Ohms!

what is the part number on the ic chip that has 4 pins on it would be the first thing I would check google search the part number to see what this device does and post it here so we can look at it as well

02680
PEm
1551 B3
6123

I can't find the datasheet, but it appears to be something like this:

Also what is the part number on the other ic chip that has 10 pins on it

54F4
5022

The voltage on the main board might be alright a few volts below because either it has no feedback which might come from the small board or this board needs a load on it to work correctly

One way to check the main board for weather or not it is functioning correctly is to get 4 automotive tail light bulbs and wire them in series and see if the power supply complaint about its load if not then definitely focus on the little board for this issue that you have with it

Thank you for recommendation. Could I get away with connecting a 220v domestic filament light bulb to it?

Can you please take another picture of the small board straight on and focus on the lettering so the image is clear so I can see the other components on the board thanks

Straight on the light was bouncing off, but I've managed to get the writing on the components in photos above. Here's an overall view:


Thank you for your help!

[stj]

i think the small board is a current regulation circuit.

[sam_sam_sam]

I then removed the small add-on board and the PSU started without chirping:

The output should have been 48V, but I don't know what to make of this reading (is it even indicative of the PSU health? perhaps only putting a proper load on it can tell).

Once I re-attach the small add-on board (even without connecting the full load!) the chirping returns:

The white terminal on this board connects to the PSU output and the red/black wires then feed the actual device.

What could this behaviour mean? Is the problem in the add-on board? Can the presence of the add-on board create a sufficient load for the problem in the PSU to manifest itself?

Tony

I would focus on this little board

Check the input pins ( the white pin connector) for a short if you find any thing lower than 500 ohms I would suspect I would go through the whole board what is the part number on the ic chip that has 4 pins on it would be the first thing I would check google search the part number to see what this device does and post it here so we can look at it as well

Also what is the part number on the other ic chip that has 10 pins on it

The voltage on the main board might be alright a few volts below because either it has no feedback which might come from the small board or this board needs a load on it to work correctly

One way to check the main board for weather or not it is functioning correctly is to get 4 automotive tail light bulbs and wire them in series and see if the power supply complaint about its load if not then definitely focus on the little board for this issue that you have with it

Can you please take another picture of the small board straight on and focus on the lettering so the image is clear so I can see the other components on the board thanks

One note I am really interested in this little board to know what it's function is and how and what it does to the main board and how it effects the output of the main board ( my hunch is that it is the current controller board ) because the description of this switching power supply says that you are adjusting the current output

[sam_sam_sam]

Did you test the capacitors off the board if not then remove them from the board and retest them

[CapLeaker]

If diodes fail, they like to fail short. The best way to test any component is to check it out of circuit.

[tester001]

Something strange happened. I've been testing continuity with a Fluke meter and couldn't get any current flowing through the diode no matter how I connected the probes (in case I mixed up the polarity):

Then a colleague tested the diode with this thingie and it now works correctly on Fluke too:


So I'm back to situation where no components explicitly show as broken. But I think I may be getting the hang of the game: desolder and test everything..
Thank you for your continued help.

[stj]

test the diode off the board,
if it's still bad then obviously replace it.
as for the caps, it really depends - if this is going somewhere hard to reach then it's better to replace the caps now than later.
but if it's easy to get to then i suppose it doesnt matter

[tester001]

in english - check the output diode

Thank you very much! After reading up more about the subject I found a diode next to the capacitors and it failed basic diode tests (wasn't passing current in any direction)

Datasheet: https://cdn.badcaps-static.com/pdfs/...1c6b8e6590.pdf

Shall I try to replace the fast recovery diode and put the capacitors back? Is it OK for 63V 470 uF capacitors to be reading 400 uF and 410 uF?

Thanks again!

[stj]

in english - check the output diode

[tester001]

Where does this little board hook up to… looks like into the secondary somewhere, as it got DC leads….

It's an LED driver PSU

I've just tested the two 63V 470 uF capacitors:
one is reading 400 uF
the other 410 uF

Would this be sufficient to cause the described fault?