Midmark Preva - Page 95

Preva Installation/Service Manual, 00-02-1577, Revision E01
92
Incorrect
kV
At times, non-invasive measurement of an otherwise fully functional system indicates
that kilovoltages may be incorrect. Kilovoltage [kV] is controlled by the
microprocessor and is not adjustable. The Preva generates kilovoltage by first
establishing a reference voltage and then comparing the feedback voltage to the
reference. Follow these steps to establish proper operation of the kV controls
1. On the Logic Board, place a voltmeter on TP8 or TP10, the Common Return, and
TP6, kV Program, as shown in Figure 67. Compare measurements to the
following chart (volts DC).
60 kV
65 kV
70 kV
4 mA
3.1
3.4
3.7
5 mA
3.2
3.5
3.75
6 mA
3.3
3.8
3.8
7 mA
3.4
3.7
NA
2. To evaluate the feedback voltages that represent the measured kV within the
system, compare the observed values in the table below. To properly observe
these values, select 1.5 seconds of exposure time and measure the DC voltages
during the exposure only. This measurement is made across TP8 or TP10, the
common return and TP3, the kV Monitor, as shown in Figure 67.
60 kV
65 kV
70 kV
4 mA
3.1
3.4
3.7
5 mA
3.2
3.5
3.75
6 mA
3.3
3.6
3.8
7 mA
3.3
3.65
NA
Values that approximately match the above tables represent a correctly operating
system. Other values may indicate that boards need to be replaced. Additional
assistance can be obtained from Midmark Technical Support.