General - TTI 1604 Service Manual

Service Handling Precautions
Service work or calibration should only be carried out by skilled engineers. Please note the
following points before commencing work.
Most of the integrated circuits are CMOS devices and care should be taken when handling to
avoid damage by static discharge.
Many of the devices are miniature surface mount 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 tools and soldering equipment specifically designed for surface
mount components are used.
Dismantling the Instrument
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. Invert the instrument and remove the 4 screws securing the case upper. Holding the case
halves together, turn the instrument the correct way up and lift off the case upper, taking
care to leave the front and rear panels in place in the case lower.
2. To remove the keyboard/display pcb unplug the 34-way flat cable from the main board and
undo the 7 nylon screws securing the keyboard to the front panel. This will give sufficient
freedom to work on the pcb but for complete removal the connection to the current range
fuses FS1 and FS2 from the main board must first be desoldered.
Note: When reassembling, use only the nylon screws originally fitted to ensure that proper
isolation is maintained between the keyboard (which is at measurement COM terminal
potential) and the front panel.
3. To remove the main board from the case lower, undo the 3 screws retaining the pcb and
lift clear with front and rear panels still connected. The keyboard/display pcb can be
removed as described above; the rear panel can be removed by undoing the RS232
connector screwlocks and the tamper-proof earthing screw.
4. To gain full access to all components on the main board remove the upper and lower
screens; replace both screens before recalibration, see Calibration section.
5. Reassemble in the reverse order ensuring that all connections are remade exactly as
before, especially the safety earth connections to front and rear panels. Use only nylon
screws to secure the pcb to the front panel.
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WARNING!

General