• Choose a category
• All
• Classic-Fiction

By Root 122 0

if necessary as dry joints are mechanically weak and can sometimes have a high electrical resistance.

Dry joints are usually the cause of intermittent faults.

On completion always switch off the soldering iron and put iron and stand in a safe place to cool down. Using side cutters trim off all unwanted component leads from the copper side of the board.

4.0 Testing

Having spent hours making your project the natural tendency is to apply power and switch it on. DON’T DO IT.

The first step should always be to remove all debris from the workbench or testing area to limit the chances of short circuits, then follow the procedure listed below:

1) Using layout and circuit diagrams check for accuracy.

2) Inspect all joints and ensure that there are no dry joints or inadvertent short circuits.

3) Switch on power supply set and check voltage levels.

4) If you are using integrated circuits check that they have not yet been inserted into the DIL sockets.

5) Connect your project to the power supply double check your connections before you switch on.

6) Using a voltmeter check voltage levels at power rails and at each DIL socket. If the supply voltage differential is less than 50v, run the tip of your finger over all the components to check for overheating.

7) Plug in the Integrated circuits stage by stage testing each stage before plugging in the next. Note it is advisable to disconnect the power supply before plugging in each integrated circuit.

5.0 Finishing

If your project is to be used in damp conditions it is advisable to coat vulnerable parts with printed circuit board lacquer.

Before starting clean and de-flux the PCB, mask any clear plastic wafer switches and integrated circuits. The easiest way to mask integrated circuits is to fit masking tape to the top of the plastic covers that are supplied with the IC’s.

It is advisable to spray lacquer in a well ventilated area if this is not possible lay newspaper across the top of your cooker and use the extractor fan to remove fumes.

When spraying apply several light coats to both sides of the board allowing drying time between coats.

SYMBOL LIBRARY