If your completed kit doesn't operate properly, here are some tips for tracking down the source of the problem:
- The timer PCB has a large copper fill area between the tracks that is connected to 0V (GND). Care must be taken not to inadvertently bridge the connection to this area when soldering. The copper fill area is coated with solder resist, but this can be chipped and expose the copper underneath. Your joints should look like the one in the picture on the left, with all the solder within the pad area. The picture on the right shows a joint with solder potentially forming a connection with the copper fill area. This joint needs to be desoldered and remade. To reduce the chance of this kind of joint, use a soldering iron with an appropriately sized tip and use as little solder as possible. Don't use the same soldering equipment you use for your plumbing.
|Good joint||Bad joint|
- Disconnect completely from the battery. Separate the boards. Remove the CPU from its socket. Using the the pin on the board interconnector nearest the corner of the board as your GND reference (it's square and the others are round), measure the resistance between this and the other connections on the CPU board interconnector. They should all be >1MΩ relative to GND. The same should be true of the display board interconnector (again, use the square corner pin as GND reference). If any of these points show a low resistance to GND, then check the joints along the appropriate track for shorts to the copper fill area.
- With the battery and display board disconnected and the CPU removed from its socket, check the resistance between the pins of the CPU socket and GND. They should all be >1MΩ apart from pins 8 and 19. If any of these points show a low resistance to GND, then check the joints along the appropriate track for shorts to the copper fill area.
- To see if the CPU is operating, insert the CPU into its socket. Connect the CPU board to the battery. With the display board disconnected, switch the unit on (the toggle switch towards you, away from the battery connector). If you press keys on the keyboard you should hear a beep from the buzzer. If not then you have a fault on the CPU board, or a flat battery.
Once you have determined which board has the problem, you can check your joints and the orientation of the components to try and find the problem.
If you continue to have problems then send an email with the results of the above tests
. If you get no response from that address within 48 hours then please try
Don't be afraid to include photos!