Preva Installation/Service Manual, 00-02-1577, Revision E01
81
Produced but
Exposure
Indicators
Detected
When no X-ray is produced, the Preva may still operate the exposure indicators.
The procedure to troubleshoot a no X-ray condition depends on which exposure
indicators are detected.
1. Activate diagnostic mode, as explained in the System Configuration section
of this manual.
2. Take an exposure.
3. Follow the appropriate procedure below:
• If no kV is produced, go to the procedure “No kV Produced”.
• If no mA is produced, go to the procedure “No mA Produced”.
• If no “I” is produced, go to the procedure “No (I) Filament Produced”.
1. On the Power Supply Board, observe that the power supply indicator D11
+350volts DC is illuminated, as shown in Figure 57. Illumination represents
proper stored energy for an exposure. If this indicator is not illuminated, it
will be necessary to replace this board.
2. On the Logic Board, measure voltages at TP1 (+8.1V) and TP9 (+24V). Use
TP8 or TP10 as Common Return. If any of these voltages are not present
after power is applied, next check voltages on the Power Supply Board.
3. On the Power Supply Board, use TP2 as a common test point to check TP1
+24 volts DC and TP3 8.1 volts DC. Then use TP5 as the common return to
check TP4 for the presence of +12 volts DC, as shown in Figure 57. Should
any of these voltages not be present, replace the Power Supply Board. If
each voltage is present, check other voltages on the Logic Board.
4. On the Logic Board, measure between TP8 or TP10, the Common Return
and, TP6, kV Program. This voltage should be between 3 and 4 volts DC. If
this voltage is not present, replace the Logic Board. If this voltage is correct,
inspect the condition of the ribbon cable between the Power Supply Board
and the Logic Board. If the cable is undamaged and seated properly,
replace the Logic Board.
5. Check the condition of the cables between the Control Unit and the
Tubehead assembly. If no X-ray occurs and no errors are displayed, the
problem may lie within the conductors of the white connector (which is
primary power to the Tubehead Assembly). If no X-ray occurs and the
attempt is accompanied by a “snap” sound, the problem may lie with the
conductors of the black connector (which is transmitting the feedback
signals). Connections for this cable begin with controls at J1 of the Power
Supply Board and J3 of the Logic Board. As shown in Figure 59, an internal
set of connections will be accessed below the distal side of the horizontal
arm and at the inside top of the Tubehead Yoke. The final set of
connections is accessed by removing the Pivot Cap located at the
attachment point of the Tubehead to the Yoke.
6. If D11 on the Power Supply Board is illuminated, power supplies are in
order, and the cable connections are correct, place an AC voltmeter across
the Tubehead connector J1 (white connector) on the black and white
conductors, request an exposure time of at least 1.5 seconds, and measure
the resulting voltage during the exposure. Presence of 130 volts AC will
require the replacement of the Tubehead Assembly. Absence of 130 volts
AC will require re-inspection of the interconnect cables for open
conductors.
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