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Hello,
I have half the LEDs soldered in to my Peggy 2, and it seems to be working well. I can upload and run sketches, and everything seems to work, with the exception of row 2. It’s not that Row 2 is just a little brighter than the other rows, something that I understand can go away after completion of construction. Rather, Row 2 stays entirely, brightly lit during running of the sketches with no discernable response at all to the sketch.I understand that the transistors control the rows, and I have checked the solder joints and don’t see anything obvious. Can anyone point me in a potential direction for troubleshooting? Thanks in advance,pIt is likely that you have a short circuit somewhere in the control section that is holding the base of one of the transistors low– or just connecting it to a neighboring signal. This could be either at the transistor itself (which you have already checked) or at the pins of U2, the LED driver that controls the second row. If you have access to a multimeter, you might be able to use that to help locate the issue.
>Using the continuity tester on my multimeter, when powered on, the + and – leads of the LEDS on Row 1 are continuous.
I’m not sure what you mean by “continuous” here. The square-hole sides are connected together in every row, and the round-hole sides are connected together in every column.>Row 1 is not ALWAYS all lit. When the device is powered on, an apparently random pattern of LEDS in Row 1 sometimes light (usually in blocks of three or four) with a few LEDS in between not lit My earlier statement that the LEDS show no response at all to the sketch may be incorrect. I can see them flickering slightly but they are so bright it’s hard to be sure.Have you finished building the Peggy yet, or are you still trying to debug it while building? If there’s a pattern in the behavior, it is likely to reveal itself more clearly when all of the LEDs are in. And, if something is flaky, try wiggling the different components to see if the transistor or one of the chips has an intermittent connection.If I understand correctly, whenever an LED lights anywhere, the LED in row 1 but in the same column as that LED lights up as well. That suggests that the transistor on row 1 is stuck in the “on” position. Using your multimeter, check to see if the base pin of Q1 (the left-most pin, connected to RB1) is stuck in the low-voltage position. If so, it’s likely that the transistor is OK, but is receiving a bad signal. Check to see if that pin is electrically connected to nearby things. Then, check the other end of RB1 to see if it might be shorted to pins 2 or 20 of U2. It *should* be connected to pin 3 of U2, and that pin alone.
By “low-voltage position” I just meant that it was held electrically low (close to ground).
> the positive pin of every LED in row 1 is in continuity with the emitter pin (right-most) of EVERY transistor.This should not be the case; compare with the other rows. The emitter of the transistors is connected to the positive power supply (“Vcc”), and Vcc should not (directly) make it into the LED matrix anywhere. The likely issue is that the collector (middle pin) of Q1 is connected to the emitter. Check on the top and bottom sides of the PCB for a short at Q1. If you cannot find an external short, try replacing that transistor.
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