TTI QL II Series, Service Manual

Page: 7 / 47

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.
Please note the following points before commencing work.
The tracks on the printed circuit boards are very fine and may lift if subjected to excessive heat.
Most of the integrated circuits are static sensitive and great care should be taken when handling
them to avoid damage due to static discharge. Also, most devices on the Control board are
surface mounted components with very fine leads on small pitches. These components must be
removed and replaced with great care to avoid damage to the PCB. It is essential that only the
proper tools and soldering equipment as recommended for surface mount components are used.
Dismantling the instrument
WARNING!
Disconnect the instrument from all voltage sources before it is opened for adjustment or repair. If
any adjustment or repair of the opened instrument is inevitable it shall be carried out only by a
skilled person who is aware of the hazards involved.
1. Remove the six screws retaining the top cover and lift clear.
2. To remove the pcbs, first improve access by unscrewing the front panel: remove the screw(s)
securing the front panel bracket(s) to the spacer in the centre of the Power pcb(s) and remove the
screws that fix the bottom edge of the front panel to the chassis. The front panel can be tipped
forward to give access to the latching connectors connecting the Keyboard to the Power pcb;
disconnect these, noting orientation.
3. To remove the Power and Control pcbs remove the two screws securing the Power pcb to the
central fan bracket and the two screws fixing the Power pcb bracket to the rear panel. Unplug the
two transformer connectors, the fan connector and any inter-pcb connections (Power to Power on
a triple output supply, and/or Power to Interface on programmable versions) noting their positions
carefully; a diagram is provided at the end of this manual showing how these connections are
made. The Control pcb is plugged into the Power pcb and both can now be lifted clear together.
4. The Display/Keyboard pcb can be removed from the front moulding after pulling off the jog wheel
and removing the fixing screws, two of which also secure the front panel bracket (four on the
triple).
5. To remove the Interface pcb from the rear panel, undo the jackscrews of the GPIB and RS232
sockets and the self-tap screw in the chassis which retains the inner support bracket.
6. When re-assembling the instrument ensure that all fixings use the correct fasteners. Replace cut
cable ties. Do not over tighten the display/keyboard fixing screws in the moulding. Check that the
fan operates.