Question 3.
An RTV student is told to carry out the following actions on the power stage of the circuit board in a dis-assembled radio receiver.
- Remove a faulty diode from the board.
- Replace the diode with a functioning equivalent.
- Trim off the extended leads of the replacement diode.
- Fix the board back and encase the radio.
(a) list two hand tools each required by the student to successfully carry out actions I, II, III and IV.
(b) name:
(i) the process of fixing the diode to the circuit board;
(ii) one material required for the fixing in 3(b)(i).
(c) describe in five steps the process of testing a crystal diode using a digital multimeter to confirm its workability.
Observation
The expected responses were:
(a) Hand tools required to remove a faulty diode from the board
(i) Soldering iron
(ii) Long nose plier
(iii) Lead sucker/ desoldering pump
Hand tools required to replace the diode with a functioning equivalent
(i) Long nose pliers
(ii) Soldering iron
Hand tools required to trim off the extended leads of the replacement diode
(i) Side cutter
(ii) Long nose plier
(iii) Cutting plier
Hand tools required to fix the board back and encase the radio(i) Screw driver
(ii) Allen Key
(b) (i) Process of fixing a diode to the circuit board
- Soldering
- Insert the diode into appropriate position (holes)
- Solder the legs to the board
- Clean off excess solder
(ii) Material required for the fixing in (b)(i)
- Solder
- Resin core solder
- Flux
- Soldering lead
(c) Process of testing a crystal diode using a digital multimeter
(i) Switch on the digital multimeter
(ii) Set the pointer of the multimeter to the diode test symbol/mode/ 
range
(iii) Insert the black probe to the com socket and the red probe to the V Ω socket.
(iv) Use the black probe to touch the lead of the diode with the band, and the red probe to touch the other lead. (It should show a reading).
(v) Reverse the connection of the probe (it should show no reading).
It was reported that majority of the candidates that attempted Question 3 responded very well. Only a few candidates could not give the required responses.