TTI CPX200, Service Manual

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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.
The tracks on the printed circuit boards are very fine and may lift if subjected to excessive heat.
Use only a miniature temperature-controlled soldering iron and remove all solder with solder wick
or suction before attempting to remove a component.
Dismantling the instrument
WARNING
Disconnect the power supply from all voltage sources before it is opened for adjustment or repair.
Capacitors inside the supply may still be charged even if the supply has been disconnected from
all voltage sources but will be safety discharged about 10 minutes after removing power.
If any adjustment or repair of the opened supply under voltage is inevitable it shall be carried out
only be a skilled person who is aware of the hazard involved. The incoming AC supply to the unit
under test should be isolated for safety by means of a 1:1 isolation transformer of at least 700VA.
High voltages (up to 400V) are always present in the primary-side circuitry which lies in a clearly
defined area at the rear of both the upper (control) and lower (main) printed circuit boards.
Removing the link at PJ10 only disconnects HV from the power FETs Q1/Q2 (Q101/Q102).
1. Remove the six screws retaining the top cover.
2. To remove the upper (control) pcb proceed as follows.
Unplug the 26-way flat cables to the front panel pcb and the 16-way flat cables to the
lower (main) pcb noting their orientation (red stripe to pin 1 corner markers on pcb).
Unplug the harnesses from the 50Hz transformer (PJ7, PJ107) and the control
connections to the main board (PJ5, PJ105) noting the orientation of the sockets (pin 1 on
the socket housing to pin 1 corner markers on pcb).
Remove the 4 self-tap screws and lift off the pcb.
3. To remove the lower (main) pcb proceed as follows. Remove the power (M3 nuts) and
sense (2-way header) connections to the front panel for both channels noting orientation;
inner (insulated) power lead is positive, red sense lead to corner marker on pcb.
Unplug the two harness connections from the 50Hz transformer (PJ1 and PJ8) and the
connection from the front panel switch (PJ6), noting orientation (pin 1 on the socket
housing to pin 1 corner markers on pcb). Remove the safety earth connection to the rear
panel; remove the rear panel (3 screws). Remove the 9 screws which secure the main pcb
support pillars to the case lower (i.e. the screws accessible
underneath the case lower)
and lift the pcb clear with its mounting pillars attached.
4. To remove the front panel pcb, first remove the six push-on control knobs then undo the 5
screws securing the pcb to the front panel and lift free.
5. Reassemble in the reverse order taking great care to ensure that all connections are
exactly as before dismantling and that no insulation creepage and clearance distances
have been compromised. Ensure that only the correct fastenings are used otherwise
earthing, and hence EMC and safety performance, may be impaired.
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