Peggy 2.2 LED pegboard
December 2, 2009 Leave a comment
1hour and plenty of tinkering around the board…
When I press on the U4, all of a sudden the whole 1st row lights up…
But then it becomes very dim and FLASHES…. luckily I remembered what I read yesterday on the forum: to short L1 or L2… and it WORKS !!!
So to summarise there seem to be 2 problems, hiding each other:
1) the U4 has a connection problem. I don’t know exactly what, I’ll try to re-solder it, but when I press on one of the corners it works properly…
2) L2 that I installed seems to be causing very dim lights and flashing… just shorting L1 (as per the forum’s instructions) seems to fix it
Now thanks to some (very) helpful and quick reply from one of the “gurus” at EvilMadScientist, I’ve started testing the U4, one of the 2 STP16DP05 LED drivers.
I switched it with U5 but the symptoms remained exactly the same.
I’ve checked the pins of the circuit and, with an OhmMeter, the connection between the front and the back, for every single one of the 24 pins…
Everything looks OK… very frustrating…
Here’s the picture with my problem:
I went back to the board and:
1) switched U4 and U5 and, sure enough, same thing happened
2) checked the U4 socket with an OhmMeter, for every pin the connection between front and back
3) put back U4 and after some tinkering I discovered than when pressing hard one of its corners the whole first row lights up !!!
4) BUT becomes very DIM and flashes…
5) I luckily remembered what I had read on the forum about this problem and shorting L1 or L2 (I have an inductor in L2)
6) I shorted L1 and it DOES work properly…
So to sum up, there were 2 problems, hiding each other:
1) the U4 did have a connection problem (I’ve simply resoldered all its socket pins and now everything looks fine)
2) the L2 didmake the LEDs DIM and flashing (just shorting L1 fixed te problem)
The problem with the U4 took a while to find, simply because, silly enough I was convinced that each of U4 and U5 controls HALF of the colums … whereas it’s obviously U4 the first 16 and U5 the remaining 9… which was corresponding EXACTLY to my board’s symptoms… doh !