Question 3
AIM: To test candidates’ knowledge of the components in the various stages of a television (TV) receiver.
(a) You are provided with components A, B, C, D and E.
(b) Identify components A, B, C and D and record in Table 2.
Table 2
Comp-onents |
Name of component |
Circuit symbol |
Stage found in TV receiver |
Function performed in the stage |
Two other components that combine with the component to perform its function |
A |
|
|
|
|
|
B |
|
|
|
|
|
C |
|
|
|
|
|
D |
|
|
|
|
|
(c) Draw in Table 2, the circuit symbol of components A, B, C and D.
(d) State in Table 2, one stage where each where each component can be found in a TV receiver.
(e) State in Table 2, one function performed by each component in the stages mentioned
in 3 (d).
(f) List in Table 2, two other components that combine with each of the components to perform the function mentioned in 3 (e).
(g) Count and record the number of pins on component B.
(h) State two steps required to remove a faulty component B from a TV receiver.
(i) Assuming components A, B, C and D are faulty, complete Table 3 with the symptoms of fault in a TV receiver in relation to the associated stages.
Table 3
Components |
Two symptoms of fault |
A |
(i) |
(ii) |
|
B |
(i) |
(ii) |
|
C |
(i) |
(ii) |
|
D |
(i) |
(ii) |
(j) Place component E on a plane surface as shown in Fig. 5.
(k) Write down the code written on component E.
(l) Measure and record the resistance of component E.
(m) State one stage in a TV receiver where component E can be found.
(n) State one function performed by component E in the stage mentioned in 3 (m).
(m) State one symptom of faulty component E in a TV receiver.
Observation
The expected responses were:
Table 2
|
(b) |
(c) |
(d) |
(e) |
(f) |
|
Name of component |
Circuit symbol |
Stage found in TV receiver |
Function performed in the stage |
Two other components that combine with the components to perform function |
A |
RF tuner |
Input stage/RF stage |
|
|
|
B |
Line transformer |
|
|
|
|
C |
Loud speaker |
Sound/audio output |
|
|
|
D |
Indoor antenna |
Input/RF stage |
|
|
(g) 10 pins
(h) Steps required to remove a faulty component B from a TV receiver
- Discharge the anode cap
- Heat up the soldering iron to melt the solder
- Remove the molten solder with lead sucker and pull component out
- Pull the component out from the board.
(i) Table 3
Component |
Two symptoms of fault |
A |
|
B |
|
C |
|
D |
|
(k) 4W8Ω2K
(l) 7.4 Ω - 9.0Ω
(m) Power stage
(n) Voltage dropping
(o) Symptom of faulty component E in TV receiver
- No power output
- Poor regulation
- Low power supply
In question 3, candidates were expected to identify unknown circuit components and state their relevance in the various stages of a television receiver. The Chief Examiner reported that the tasks in this question seemed to be very popular among the candidates and majority of the candidates that attempted the tasks responded quite well.