Aloha

I finally got all the chips & LEDs soldered into my Peggy 2.0 - its been sitting in the ToDo pile for far too long. I fired it up today in time for the Lady Ada's G+ Hangout & Show&Tell. Unfortunately there are some issues with it. I think I have several issues and would like some advice on approaches to finding and solving these...

First here's a picture of my board:


The driver chips are on left of this pic, so rotate your head to get correct semantics of row/column.

First there is a quite noticeable difference in brightness in various rows, and some rows dont light up at all. There are also several unlit partial columns at the top (right in image).

It may be that the third row from bottom (left) is installed backwards. What test should I try to verify this?

The 7th from bottom (left) row (column) is dark in this image but other times it has lit properly.

It was suggested (by Limor) that cold solder joints may cause some of the variation in brightness. Would that affect an entire row, or just a single LED?

It was also suggested that some of the partial column issues may be due to broken traces. I think I can see the copper on some of these so I'll try soldering a bridge. Detailed inspection means breaking out the microscope.

Aside from visual inspection, what do you recommend for chasing down the failure to light and dimness issues?

Thanks

Looks like you have more than one problem; I'd suggest tackling them one at a time. Start with the partial columns. Something went very wrong at those locations-- either a broken trace or a short circuit. Start looking there, and see what went wrong.

For the individual LEDs that are out, check the soldering at that particular point.

For the full rows that are out, check the soldering at the demultiplexer chips (the ones on the right hand side), and the transistor and resistor associated with each of those two rows. If you suspect that an LED (or more) is backwards, try putting a new LED (backwards) across the pins of that location from the back side.

Don't unsolder things unnecessarily. You've got a number of bad connections here, it looks like, probably not bad components.