Question 2
AIM: To test the candidates’ knowledge on different sections of colour CRT Television receiver.
- You are provided with a colour CRT Television receiver.
- Let the Supervisor open the back cover of the Television receiver.
- List two tools used by the Supervisor in removing the back cover of the Television.
- State the specification of the Television in terms of:
- model;
- input supply voltage;
- supply frequency;
- input power rating.
- Identify one transducer in the audio section and record in Table 2.
- Write in Table 2, the function of the transducer identified in (e).
- State two physical features of the transducer and record in Table 2.
- Identify two components found in the audio section and record in Table 2.
- Repeat steps (e) to (h) for the video section
- List two faults associated with the section specified in Table 2.
Table 2
Section |
Transducer |
Function of transducer |
Physical feature of transducer |
Components identified |
Fault associated with section |
Video section |
|
|
|
|
|
|
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|
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Audio section |
|
|
|
|
|
|
|||||
|
- State two precautions taken in carrying out the activities.
Observation
The expected answers were:
(c) Tools used to remove the backcover of television
- Screw drivers
- Allen key
- A pair of pliers/long nose pliers
(d) (i) Model
- 21SB1RG-TB
- KV-LS21T99
- Any other acceptable model
(ii) Input supply voltage - 110 – 240V
(iii) Supply frequency - 50/60Hz
(iv) Power rating - 40W – 85W (varies with model)
Table 2
Section |
Transducer |
Function of transducer |
Physical feature of transducer |
Components identified |
Fault associated with section |
Video Section |
Cathode Ray Tube (CRT)
|
Converts electrical energy to video/picture/light
|
-HT input cap
|
-Inductor/coil |
-no picture |
Audio Section |
Speaker
|
Converts electrical energy to sound
|
-magnet
|
-resistor |
-no sound
|
(k) Precautions in carrying out the activities
- I ensured the use of the right tools for the right jobs.
- I disconnected television set from power source before opening.
- I discharged the anode cap of the H.T. transformer.
- I discharged the high voltage capacitors.
- I wore protective dressing.
- I used insulated tools.
- I grounded/earthed the high voltage sections.
Candidates were expected to read off the specification of the Television receiver at on back cover. Basically, only the Cathode Ray Tube and the loudspeaker can convert from one form of energy to the in the video and audio sections respectively. Therefore, candidates were expected to identify them as transducers.