Finding the wrong part at a loooong led strip, part works fine, part flickers, all parallel...

[edugimeno]

Hi There!
I'm trying to help my friend who owns a restaurant be just bought.
He has a very long LED strip running along all the walls and columns. The strip is attached facing down 2in above the floor, using a wall panel that ends in a metal rail that finishes the panel underneath
It's stuck using, I guess, the 2 sided tape that comes with the strip
The issue is that like 1/2 of the full length, including 1/2 one wall, another entire wall, and one column, flickers after 4 or 5 minutes ON. Particularly it flashes staying OFF most of the time and flashing ON for 1 tenth of second every 2 seconds, aprox
We checked the transformer and it seems ok, with constant voltage all time. One thing that caught my attention is that this 12V, 21A transformer, using a multimeter is only providing 5Amps for this entire led strip. And we made sure there's no other transformer as as soon as we took one of the 12V leads out of it, the entire (working fine part and flashing part) would shut off, so it all comes from it, but looks like too low current to me for a led strip that's probably 20-30m long
So the wiring is not all continous, we went down underneath the part where the OK leds are and where the FLASHING leds start, and we found that it's another section, with no connection between both, and the second one is being powered from a further connection far from there, with a tight junction of wire coming and hidden behind the wall panels. We realized that there were several connections coming down behind the wall panels powering different parts, probably the builder bought short strips and had to power them all individually, or maybe he wanted to avoid voltage drop by not going all in cascade.

Thorough and manual diagnosing the strip is a little hard and annoying, as it's all upside down so close to the floor, we need to move all the restaurant tables and use a mirror to see the connections and leds.

Also I measured the voltage at the failing section and V goes up and down around 4-8V (digital, slow multimeter, probably would reach to 12V, flash, and then drop)
Question is:

• Provided the information you've read, and if you have worked with these led strips, what type of issue can you look at?
• Assuming the transformer is OK is saf, right? Provided hundreds of LEDS work fine with no flickering
• Should I look for a strip short into the aluminium plate?
• Should I look for a shorted LED? If so would it look blackened?
• How can one part of the strip be 100% stable while another part is flickering, when it's all connected in parallel?
• Any other smart hint to help diagnose where's the failing part?

We can definitely replace the whole strip but this would take too long, detaching the strips from the plate, removing all solders everywhere, and redoing the thing without having found the real issue...

Thanks in advance!

[stj]

power the flashing section with some fresh wire to test it.
it sounds like a wiring problem.
you have to power the strips every 5-10m because of voltdrop - thats directly from the manufacturers instructions.
if you have a 10m strip you power both ends for even brighness for example.

[edugimeno]

Ok yes this is something I can try and it's not that hard, as there are +/- leads everywhere at the cut points...
So you think some power points have a bad connection? Don't you think a faulty led would do this?
What would be your procedure, I mean, if I start applying 12V to all points in the faulty section, what would I do if I find a point where the extra 12v stops the flickering?

THANKS!

[stj]

just connect 12v to the flickering section and see if it works o.k.
if it does then you need to find the bad wire joint.
if an led fails it shouldnt effect the rest because they are in parallel

[edugimeno]

Thanks, but the problem is that the failing section is very very long and implies 2 large walls and 2 columns (4 sides each obviously) , hard to find where the connections come from (somewhere behind the panels, can't see them) and where the sections are joined together. I will give it a try thou
Thanks

[stj]

if it's that long you need to inject power at several points along it's length.
if not then it may blow a track open from the current flow!

[edugimeno]

Ok I will start supplying 12V on all connection leads I see and try to find out whats wrong after I see the results
Thanks a lot!