Most common mistakes
- The most common reason for a kit not working is poor soldering, so-called 'dry joints'. Solder should cover a pad completely and be smooth and shiny. If the solder forms a ring around a wire (like a doughnut), or has formed a blob above the pad then more solder is needed. If a solder joint is dull-looking or has an uneven surface then it should be re-heated.
- Hold the board up to the light. If any light shows through a hole then more solder is needed.
- A bridge is where solder has crossed between tracks causing a short circuit. Watch for component legs that have been bent flat onto the board and soldered at multiple points. These are sometimes hard to spot. Cut away wires that are shorting.
- Large blobs of solder are liable to cause short circuits, particularly with chip sockets.
- The second most common reason for a kit not working is that components have been inserted into the board incorrectly. Check all the components are in the right places by comparing component values with the construction sheet. Note that components themselves rarely fail so that is unlikely to be a cause of a kit not working.
- Transistors are in backwards. Match the semi-circular shape of the component to the symbol on the board.
- LEDs are in backwards. Match the flat on the rim of the component body with the line in the symbol on the board. Note that the LEDs in beginners kits have a wider hole spacing to avoid short circuits between the legs, and hence will not push all the way down. The LEDs in other kits should be flush with the board, reheat solder joints and push component down if not so.
- Electrolytic capacitors are in backwards. Check the stripe on the component body is next to the minus sign on the board.
- Diodes are in backwards. Check the black band on the component body is next to the plus (or sometimes 'k') sign on the board.
- Resistors have been mixed up. Check the colour codes against the construction sheet, it is easy to confuse them if one is not familiar with the colours used.
- The battery snap is reversed. Red is positive and black is negative. It is not critical if the battery support holes have not been used, but the kit will not be as durable.
Less common mistakes
- A transistor's legs have been crossed over above the board, or are touching.
- A component leg is not making it through the hole in the board. Melt the solder joint and feel for the tip of the wire with the soldering iron.
- If too much heat is applied then tracks can lift from the board. Repair with a piece of wire cut from a component leg.
- Very occasionally hairline breaks occur in tracks. Hold the board up to the light to spot them. Hairline cracks can be repaired by soldering over the gap.
- Solder splashes or streaks causing bridges between tracks where the tracks are close together. Melt through the solder with the iron.
- If solder has been repeatedly heated then it loses the ability to make a good joint. It is better to remove the solder completely with a solder sucker and then to re-solder.
- The battery wires have broken inside the snap. Check power is getting to the board. An LED soldered to a 470R resistor (yellow, purple, brown, gold) makes a good battery tester. Touch the tracks on the board leading from the battery (try both ways around).
- Piezos are quite fragile components and their leads can be broken internal if roughly handled. Connect a spare battery snap to a battery and touch the leads briefly against the legs of a suspect piezo. If the piezo is working a crackling sound should be heard.
- A chip socket is soldered in backwards (notch in the socket not matching notch in the symbol on the board). Rather than de-soldering the socket which is tricky, simply reverse the chip in its socket (as it is matching the notch in the chip to the notch in the symbol which really matters).
- A chip is not pushed fully into its socket, or a leg is bent underneath.
Specific kit problems
- Flashing Lights - it is sometimes necessary to remove the battery, wait a couple of seconds, then re-connect the battery. It may well then start flashing.
- Wonky Wire - it doesn't actually matter which is the wand and which is the wire. In other words they can be soldered to either hole.
- Bagpipes - if all the notes work up until one point, check the soldering of the corresponding keyboard resistor.
- Decisions Decisions - if the flashing is uneven and biased towards one side, then the 220u capacitor is probably not in the correct central position on the board.