Originally Posted by
metric_taper
Well the component side of the board is facing away. Easy to see a transformer connected to the mains, with 3 wires. This has the white wire as a center tap of the secondary, so they are doing a full wave rectification. I can see on the PWB silkscreen where the three wires go through, one is labeled CT for centertap, and this looks to also be the ground reference connection as the circuit trace wraps around the board. I don't see any cold solder joints, but that may be the camera resolution or hidden by munge.
I would look for a loose connection as the photo shows it's working now. Check out all the solder joints. You could touch the ones up in the power supply area of the board around where those low volt power wires are going through. Can you pull the board back to see the other side better. Look for any damaged capacitor, or lead that is broken. There must be 2 diode at least from the blue wires to a positive connection, I'm guessing they are using a fixed regulator, that would be a 3 terminal part, this would take the rectified voltage from ~8-12VDC down to +5VDC.
When it flashes, does it loose the time setting? If so, then I'm guessing the main power is the problem, if not, then it might be the supply return wire between the boards.
Start by inspecting all solder connections on each assembly and carefully look at connections between the assemblies.
Good luck.
Bookmarks