Identify the transistor type
Transistors can be used for switching or amplification, but different types require different explanations. A BJT example should not be transferred unchanged to a MOSFET. Begin with the exact component identity and its documented terminal arrangement.
Draw the control and load separately
On a paper training circuit, use different colours for the control path and the path supplying the load. Ask which observation would show a command arriving and which would show the load responding. This separates a control question from a downstream-load question.
Avoid visual replacement logic
A three-terminal package does not identify a unique transistor or approve a substitute. Record the symbol, package and relevant ratings from documentation. Let a qualified instructor select any powered demonstration. The objective is to explain the relationship between control and response, not to memorise a single “good transistor” meter number.
The load does not respond to a command
A missing response could involve control, supply, the switching path or the load itself. The paper diagram helps list those possibilities. It does not justify replacing the transistor until the relevant evidence distinguishes the paths.
Your practice record
- Device type and pinout
- Control path marked
- Load path marked
- Required evidence before replacement
Sources and further reading
Manufacturer and technical references for the checks discussed in this guide. Follow the instructions for your exact device and equipment.
Repair procedures involve heat, electricity, fragile parts and customer data. Practise under qualified supervision and work only on devices you are authorized to service.