6 PREVENTIVE MAINTENANCE
Technical manual Planmeca ProX 33
6.6 Measuring KV / MA signals (invasive testing)
The manufacturer does not require the invasive testing. The invasive test must only be
performed if the local authorities require it.
An invasive method should be used for checking the tube current (mA), and can be used
for checking the kV. This method requires that the covers around the tube head assembly
are removed. The analog feedback voltage signals can be measured with a calibrated
multimeter.
1. Unscrew the two M4x20 DIN 7984 fastening screws of the cone.
2. Remove the tube head front cover and the cone.
3. Unscrew the six fastening screws of the tube head cover and remove the cover.
4. Attach sprung hook test leads from multimeter to P1-connector pins 1 (negative kV) and 2
(positive kV) in the tube head PCB..
5. Set multimeter to DC voltage mode with a measurement range of 1 to 5V signal level.
Take 2 seconds exposure with desired kV setting. Selected mA value has no effect,
however lowest possible mA should be used to minimise the amount of unnecessary
radiation. When the voltage reading has been stabilized, record it.
Actual tube voltage (in volts) = 21 672 * measured feedback voltage (in volts)
The resulting tube voltage should be within ±5% of the voltage indicated in the user
interface.
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