6
General
Service Handling Precautions
Service work or calibration should only be carried out by skilled engineers using high quality test
equipment. If the user is in any doubt as to his competence to carry out the work, the instrument
should be returned to the manufacturer or their agent overseas for the work to be carried out.
This simplified service guide only details the routine calibration procedure and the dismantling of
the instrument to PCB assembly level. If a PCB assembly is suspected as being faulty it should
be returned to the manufacturer or their agents overseas for repair or replacement. The Parts
List gives the part numbers of each PCB assembly, together with the mechanical parts and
fasteners that can be easily replaced by the user.
Dismantling the instrument
Note that calibration of the oscillator frequency does not require the instrument to be opened.
Refer to the procedure in the next section.
1.
Disconnect the instrument from all input signals, the USB connection and the AC adaptor.
2.
Unclip the front bezel by gently pulling the centre of each long edge up and forward.
3.
The case halves are held together by 4 plastic push-rivets.
4.
Lift off the case upper, leaving the front and rear panels in the base of the unit.
The instrument can be operated in this condition for fault diagnosis. If adjustment of the C
input threshold setting is all that is required, no further dismantling is necessary.
5.
Otherwise, disconnect the ribbon cable from the rear of the Main (front panel) PCB.
6.
Before removing the rear panel or the Battery/USB PCB, note the position of the
grounding spring attached to the USB socket. The PCB is attached to the case lower with
4 screws. To avoid short-circuiting the batteries, do not place this PCB on a conducting
surface. When reassembling, take care not to damage the USB spring.
7.
To remove the Main PCB from the front panel, first pull the knob off its shaft, lift the Front
Panel assembly from the base of the unit and lay it face down on a soft surface to avoid
damaging the LCD. Keeping the metal panel flat and upside down, remove the screws
holding the PCB to the front panel and lift it off, leaving the loose keycaps in the metal
panel. Collect and store the keycaps for reassembly.
8.
The C input PCB may be separated from the Main PCB by removing the nut from the N-
type connector and pulling the PCB backwards off the connecting pins. On reassembly,
align these pins carefully. The washer fits between the flange of the N-type connector and
the rear of the Main PCB. Retighten the nut firmly, to put the washer under compression.
9.
Reassemble in the reverse order. Take care when reassembling the Main PCB to the
metal front panel that all of the keycaps are correctly aligned. Connect the ribbon cable
and test the unit for correct operation before reassembling the case.
Use the blade of a small screwdriver to remove
the snap-lock rivets as follows:
First, ease out the head of the rivet using a fine
screwdriver blade under the edge of the head
(Fig.a). With the rivet head fully out, the body
of the rivet can now be eased out with the
screwdriver blade and removed completely
(Fig.b). To re-assemble, fully re-insert the body
of the rivet then push in the head to lock it.