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tree bulb on the Main channel should come on for two seconds then turn off. To test the CHB
channel, repeat the procedure, but hit "B" key to trigger the CHB channel. The CHB light
should come on for two seconds, then shut off. If both of these work, then your Eggtimer is
100% operational.
Troubleshooting
If your Eggtimer doesn't work after assembly and testing, take a deep breath, get out a
beverage to clear you mind, and start troubleshooting...
Check Your Solder Joints
The very first thing you should do is to check out all of the solder joints under a lighted
magnifier. The most common reason for things not working are solder bridges, i.e. putting too
much solder on the pads and shorting two adjacent pads together. You can also get into
problems by bridging pads with "vias" on the board, the smaller holes that don't have any
components soldered to them. Most of the holes and the pads are very small, so it doesn't take
much solder to get a nice "tented" solder joint. If you get a solder bridge, heat it up and use a
solder wick or a vacuum bulb to remove the excess; afterwards, we recommend resoldering the
joints.
Another thing to look out for is "cold" solder joints, they look dull and blobby compared to a
nice shiny "tented" solder joint. If you have a cold solder joint, it won't conduct well; at the
low power that the Eggtimer uses this could easily keep things from working. If you have a
cold solder joint, heat it up and put just a little bit of solder on it, the main idea is to get a little
more flux on the joint. If you have separate flux, you can use that in place of the solder. If
there's too much solder, use a solder wick or (preferably) a vacuum bulb to remove the excess,
then heat it up and resolder the joint.
Check Your Component Polarity
Most of the components aren't polarized, with some notable exceptions. The outline of the
parts is silk-screened on the board, so you should be able to see readily if you have a
component soldered in backwards. Components that are polarized are:
• The 28-pin processor chip; the notch needs to face to front of the board (towards the header)
• The opto-isolators; the notches need to face up
• The transistors, the plastic side should be laying against the bottom of the PC board with the
tabs facing forwards (towards the header)
• The 10uF electrolytic capacitor, the side marked "-------" should be OPPOSITE the side
marked "+" on the board (away from the processor chip).
• The LEDs, the long leads should have been inserted in the pad marked "+". Unfortunately,
once you clip the leads it may be difficult to tell if you have inserted it correctly.
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