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

[tester001]

Dear Badcaps forum members,

Hope that you are all well!
I am a newbie on a mission to figure out the cause of the PSU making a "chirping" noise:

Having searched for this symptom online I have found some indication that failed capacitors may be an issue. To help with the troubleshooting, I have tried to isolate the problem and disconnected the PSU from the rest of the device - the chirping remained.
I have then found that the whole PSU (apart from a small add-on board) can be replaced, and there is even a datasheet for it: https://cdn.badcaps-static.com/pdfs/...72e3c7c9cd.pdf

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?

Thank you in advance!

Tony

[stj]

the small board may regulate the current.
it's a fixed but ajustable current supply, so the voltage can move around a bit.

i would test the supply without the small board by using a light bulb - 25w or 40w, as it's only rated to 60w.
a old style filament lamp - not a halogen or led etc.

[tester001]

i would test the supply without the small board by using a light bulb - 25w or 40w, as it's only rated to 60w.
a old style filament lamp - not a halogen or led etc.

Thank you for the suggestion! You mean a 48v/25W filament light bulb would do for the test, correct? Does it have to be a 48V bulb or any filament bulb between 25-40W?

[stj]

240v is fine - only the wattage matters

[tester001]

I've connected the output of the PSU to an old projector bulb (8V 50W) and got the "chirping" again!


Do any caps on this PSU look like they need replacement? If not, should I desolder them one-by-one and test using a capacitor meter?





Thank you for your help so far! Happy to carry out more tests and learn

[tester001]

I have no clue of what I'm looking for, but I used the search on this website and found this:


Does this mean that the pictured caps are bad and should be replaced?

[stj]

8v lamp on a 48v supply?
i'm kind of glad it didnt work or you would be sweeping up glass!
you cant tell if a cap is good by looking, and YXF is low end for a psu - i would be using rubycon ZL or panasonic FR

[tester001]

8v lamp on a 48v supply?
i'm kind of glad it didnt work or you would be sweeping up glass!

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

Thank you, I will de-solder them and get them tested (will check online for methods)

[CapLeaker]

Usually a chirping in the power supply means there is something shorted in the secondary, as the PSU starts, shuts down, starts again and shuts down again. Over and over, wash rinse, repeat.

[tester001]

something shorted in the secondary

Sorry, I'm a total newbie. What does 'shorted in the secondary' mean?

[CapLeaker]

The low voltage side of the power supply. Just saying IF there is something wrong in the primary, it would have exploded in your face or there is an open circuit somewhere and is dead as a rock.
So the primary side works. The low power secondary has something wrong with it, Where does this little board hook up to… looks like into the secondary somewhere, as it got DC leads….

[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?

[sam_sam_sam]

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

[stj]

in english - check the output diode

[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]

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]

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.

[CapLeaker]

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

[stj]

i think the small board is a current regulation circuit.

[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!