stiebz Posted May 20, 2010 Report Share Posted May 20, 2010 Hello, I had finished my Sammich and everything seems to be working OK, except that the top right row of LED's is not doing anything. Since it is a complete row of LED's not working I expected this to be simple to trouble shoot, but so far no luck. Can't see anything wrong with my soldering. Switching the 2x 74HC595 did not change anything. Any tips on what else I need to check ? It's making nice noises already, but would be nice to have the LED's fully operational too... Many thanks in advance ! Steven Quote Link to comment Share on other sites More sharing options...
Wilba Posted May 20, 2010 Report Share Posted May 20, 2010 Maybe this picture can help. You can see where the LED cathodes for the top right row are connected to the 74HC595. It's possible the solder joint there is bad, or there's a short somewhere to another pin. Test connectivity between the LED leads and the pin of the IC from the top (don't assume the IC socket pin and the IC pin must be connected). Quote Link to comment Share on other sites More sharing options...
stiebz Posted May 20, 2010 Author Report Share Posted May 20, 2010 thanks for that clear drawing ! The connection between the pin (7) of IC3 is connected to LED's, so that seems to be OK. So it should be a short? What I noticed is that there is no resistance between pin 7, 9 and 14. Between 9 and 14 seems normal, but not sure why it is also interconnected with pin 7, I can not see any short and they are quite far away from each other... thanks ! Steven Quote Link to comment Share on other sites More sharing options...
Wilba Posted May 20, 2010 Report Share Posted May 20, 2010 Are you measuring this "no resistance" with the IC installed? If yes, take out IC3 and try again. See if there are any shorts between adjacent pins of IC3 socket (and pin 7, 9, 14, I don't know why you checked these before but keep checking things again to find anything that isn't right). Try also manually lighting the LEDs via the pins of IC3 and IC4 sockets (remove the ICs). You can connect one of pins 2,3,4,5,6,7 of IC3 to ground, then connect one of pins 15,1,2,3,4,5,6,7 to 5V. This should power one LED of the matrix. You can take 5V from pin 16 and ground from pin 8 of either IC3 or IC4 sockets. Do not put too thick a wire into the IC socket pins or they will become looser and won't make good contact with IC pins afterwards. Something like a cut resistor lead is OK, or the solid core wires used in prototyping "breadboards". Quote Link to comment Share on other sites More sharing options...
stiebz Posted May 21, 2010 Author Report Share Posted May 21, 2010 Found it ! I had somehow managed to bend pin#9 of the IC socket so it was touching the lane going to the LED's. Thanks for your great help! Steven Quote Link to comment Share on other sites More sharing options...
Wilba Posted May 21, 2010 Report Share Posted May 21, 2010 Good to hear it works now, but I don't understand what you mean... can you draw it on the image I uploaded in the previous post? Quote Link to comment Share on other sites More sharing options...
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