Ever work on a stoplight? 
I've got an LED module from a stoplight (was working fine when I first acquired it, now the green module has issues) that has a "delayed-on" condition. Instead of the usual instant on, as it used to be and as the red/yellow modules are, it takes around 2 seconds for the LEDs to light right now. They come on instantly, at full brightness, but almost exactly 2 seconds after power was applied.
I haven't done a lot with it, as I'm not the best at power supply troubleshooting, but I did measure the DC voltage between Vcc/Gnd for the MC33262P chip and it seemed to explain a bit what was going on -- voltage rose slowly from 0 to 15.7 volts (took around 3-4 seconds) but the second it hits 12-13v, the LEDs light up instantly.
I see the MC33262P has an undervoltage lockout feature in it (lower threshold is 8V, upper threshold 13V), but I don't know exactly what that means / if that means simply that output is disabled until Vcc reaches 13V? That would seem to match the symptoms.
Regardless, I would like to figure out why the voltage is rising slowly instead of instantly like I believe it should be.
ALSO, I should mention, there were/are two resistors (I'll mark them in the pictures) that are disconnected on one side, but they are in spec (not burnt or blown). I don't see how they would get disconnected/broken on their own, and the wire on those two looks completely fine otherwise. Is there any chance that they were cut on purpose during manufacturing? My only thought was the same board was used for different purposes or something, otherwise I would replace the resistors obviously.
Lastly, there are some signs of moisture that you'll see in the picture. This obviously may have been a cause of the problem. There are areas of rust by some of the resistors, etc., but the connections on others (besides the two pointed out) appear fine and the resistors I've tested so far look to be in spec.
I've got an LED module from a stoplight (was working fine when I first acquired it, now the green module has issues) that has a "delayed-on" condition. Instead of the usual instant on, as it used to be and as the red/yellow modules are, it takes around 2 seconds for the LEDs to light right now. They come on instantly, at full brightness, but almost exactly 2 seconds after power was applied.
I haven't done a lot with it, as I'm not the best at power supply troubleshooting, but I did measure the DC voltage between Vcc/Gnd for the MC33262P chip and it seemed to explain a bit what was going on -- voltage rose slowly from 0 to 15.7 volts (took around 3-4 seconds) but the second it hits 12-13v, the LEDs light up instantly.
I see the MC33262P has an undervoltage lockout feature in it (lower threshold is 8V, upper threshold 13V), but I don't know exactly what that means / if that means simply that output is disabled until Vcc reaches 13V? That would seem to match the symptoms.
Regardless, I would like to figure out why the voltage is rising slowly instead of instantly like I believe it should be.
ALSO, I should mention, there were/are two resistors (I'll mark them in the pictures) that are disconnected on one side, but they are in spec (not burnt or blown). I don't see how they would get disconnected/broken on their own, and the wire on those two looks completely fine otherwise. Is there any chance that they were cut on purpose during manufacturing? My only thought was the same board was used for different purposes or something, otherwise I would replace the resistors obviously.
Lastly, there are some signs of moisture that you'll see in the picture. This obviously may have been a cause of the problem. There are areas of rust by some of the resistors, etc., but the connections on others (besides the two pointed out) appear fine and the resistors I've tested so far look to be in spec.
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