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Fien1989
Gelehrter
230 Beiträge
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Half column of LED‘s stopped working from a DOT-LED sign, 09 Feb. 2016 00:25
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I‘ve a Gorba DOT-LED sign which has a half column of LED‘s (8) that spontaneous stopped working after the sign was powered on for about 1 hour earlier this day
How are these LED‘s connected in the circuit? I want to try repairing it. Any idea‘s which part can be defective?
I know if one LED gets loose/break off, all 8 LED‘s of a half column will go off. But in this case all LED‘s are still intact.
This sign has this dot-board:
< Dead image links >
Geändert von Fien1989 am 9.Oct.2016 19:08
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Grzegory
Adeliger
255 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 10 Feb. 2016 07:56
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Hey
This failure is often also displays Lawo.
Cold February for a board panel.
Removing these LEDs can be difficult, they are glued to the flaps FLIP DOT
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Fien1989
Gelehrter
230 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 26 Feb. 2016 21:40
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Are there no schematics of the LED circuit to try repairing it?
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Jens-MuM
Senator
548 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 26 Feb. 2016 23:20
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It is XY5L-Monosystem and the producer of the boards was the same for Gorba and LAWO - so they have the same probs...
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Fien1989
Gelehrter
230 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 26 Feb. 2016 23:45
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But normally a LED circuit only contains some LED‘s and a resistor connected to a power supply.
In this case the LED‘s are grouped by 8 and connected in serie. I think they must go to a resistor-circuit, but I can‘t follow the traces because they are below the dots. With a circuit-diagram maybe it‘s repairable...
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Brose-Matrix
Gelehrter
246 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 27 Feb. 2016 09:35
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I do not have this board but similar it should be.
It is also possible that the common pin of the SIL-resistor is connected to "minus" and the polarity of LED’s in this case too.
What is the designation on the SIL-resistors?
A circuit diagram you will not find. You have to create the circuit diagram by measuring.
Possibilities for failure:
Cold soldering point, defective resistor or LED, broken connection to LED
Check the voltage drop at the components.
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Mattze17
Bürger
64 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 28 Feb. 2016 20:17
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check the Drivers, seems to be a Driver had a defektive port....
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Brose-Matrix
Gelehrter
246 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 01 Mar. 2016 09:07
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check the Drivers, seems to be a Driver had a defektive port....
As far as I can remember, there are no drivers for the LEDs on the PCB. All LED rows are supplied together via a pulsed current source. The rows are only decoupled by resistors.
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Fien1989
Gelehrter
230 Beiträge
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RE: Half column of LEDs stopped working from a DOT-LED sign, 05 Mar. 2016 02:38
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Brose-Matrix:
I do not have this board but similar it should be.
It is also possible that the common pin of the SIL-resistor is connected to "minus" and the polarity of LEDs in this case too.
-
What is the designation on the SIL-resistors?
A circuit diagram you will not find. You have to create the circuit diagram by measuring.
Possibilities for failure:
Cold soldering point, defective resistor or LED, broken connection to LED
Check the voltage drop at the components.
The SIL-resistors has the text "LC81 2700G S 9913" on them. There are 8 of them on a dot-board.
I already have resoldered the connections from the LED-strip to the PCB, so this won‘t be a cold joint. But I forgot to do this on the SIL-resistor connections. I will check this next week when I have time to disassemble the sign again.
The LED‘s itself are very small SMD and break off quite easy, I will go try to measure them 
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Brose-Matrix
Gelehrter
246 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 05 Mar. 2016 09:30
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The SIL-resistors has the text "LC81 2700G S 9913" on them.
The datasheet: www.datasheets360.com/pdf/-4136789886603541640
2k7, 0.125W with common pin (bussed)
Geändert von Brose-Matrix am 5.Mar.2016 9:56
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Fien1989
Gelehrter
230 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 09 Mar. 2016 02:42
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I‘ve checked the board today. The positive is connected to the common pin of the SIL-resistor.
Both the resistor and the connections are still good, but i‘ve found one of the LED‘s was defective and doesn‘t pass the current to the next one so all the 8 LED‘s in the serie doesn‘t work.
Because I don‘t know where to get replacement LED‘s, I just have desoldered the LED and replaced it with a bridge-wire. Now the other 7 still work.
It doesn‘t look great, but 1 dark dot is better then 8 dark dots...
Can these LED‘s (with the same size, color and brightness) ordered somewhere? If I can found 2 of them, this sign can be back working 100%.
< Dead image links >
Geändert von Fien1989 am 9.Oct.2016 19:08
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Grzegory
Adeliger
255 Beiträge
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RE: Half column of LED‘s stopped working from a DOT-LED sign, 09 Mar. 2016 07:00
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Hallo
Me Ich benutze die gesamte Matrix LED-Streifen einfacher ist und Werke
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