Rowan Posted March 14, 2015 Report Share Posted March 14, 2015 (edited) I've just built a TPD for my MBSEQ and have a problem with one of the Red LED columns. The first colum of Red LEDs on the the righthand LED matrix are always on, apart from the bottom one. Strangle, when I power on the device and the text scrolls across the matrix the problem isn't there. I'm guess the problem is caused by a short/open connection somewhere but I really don't want to remove he LED matrix unless I have to. Has anyone got a idea as to where the fault could be? Edited March 15, 2015 by Rowan Quote Link to comment Share on other sites More sharing options...
Phatline Posted March 14, 2015 Report Share Posted March 14, 2015 i had such behavior by a led-matrix built of single leds... i plugged the pins in the false DOUT-Registers.... you cant plug it into the false doutregisters... because you have a ready built pcb... so i think: a: wrong LED-Matrix (common katode/anode?) b: if possible false connected LED-Matrix > solderede 180° wrong... c: you have to change the software you use... Quote Link to comment Share on other sites More sharing options...
Rowan Posted March 15, 2015 Author Report Share Posted March 15, 2015 i had such behavior by a led-matrix built of single leds... i plugged the pins in the false DOUT-Registers.... you cant plug it into the false doutregisters... because you have a ready built pcb... so i think: a: wrong LED-Matrix (common katode/anode?) b: if possible false connected LED-Matrix > solderede 180° wrong... c: you have to change the software you use... Thanks for the suggestions. A & B: I'm pretty sure the the anode/cathode are correct as all the other LEDs in the matrix work correctly. C: I'm using MBSEQ 4.088 that I compiled myself, I might roll back to the offical 4.087 release and see if that makes a difference. Quote Link to comment Share on other sites More sharing options...
Rowan Posted March 16, 2015 Author Report Share Posted March 16, 2015 I've rolled the firmware back to 4.087 and the problem persists so I guess it must be a hardware problem. Now I need to decide if I can live with the problem or remove the LED matrix and risk destroying the unit. Quote Link to comment Share on other sites More sharing options...
ilmenator Posted March 16, 2015 Report Share Posted March 16, 2015 Hi Rowan, I cannot wrap my head around this right now, so I can't tell you which joint exactly is broken, but it certainly sounds like one leg of a shift register is not making contact with the PCB. The welcome text doesn't use the lowest row of LEDs, so I guess that's why the problem doesn't show when you switch on the unit. If you have proper desoldering equipment I would go ahead and try to fix the problem - without a desoldering gun I'd probably just leave it as it is now. Best, ilmenator Quote Link to comment Share on other sites More sharing options...
Rowan Posted April 9, 2015 Author Report Share Posted April 9, 2015 (edited) I spent some time on this tonight and I've fixed the problem. Though I'm not 100% sure, I think the actual LED matrix itself was faulty. I removed the matrix and tested all the joints with a meter and everything was fine. I inserted the matrix back into the PCB without soldering it in to see what would happen and some of the LEDs in the column in question came on. As I had another LED matrix at hand i put that in the PCB and the fault didn't occour, so I'm putting the problem down to the matrix. I've now replaced both LED matrices with new/better quality units and it's working perfectly. Edited April 9, 2015 by Rowan Quote Link to comment Share on other sites More sharing options...
ilmenator Posted April 10, 2015 Report Share Posted April 10, 2015 Good to hear that you managed to fix the problem! I was quite convinced the problem was due to a bad solder joint on one of the shift registers, but it certainly sounds like it was the LED matrix now. Where did you source the faulty LED matrix - just so we know what to avoid? Quote Link to comment Share on other sites More sharing options...
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