GE Alpha RT 32551, Руководство по установке

Страница: 48 / 99

4 Alpha RT softstart procedure
42 GE Healthcare 32551-IMG rev 6
4.10 P
REHEAT AND M
A-
REGULATION CHECK
1 Connect the oscilloscope probe on the FILAMENT CONTROL board to
test point TP4 (mA feedback, TP12 or GND ).
2 Check that large focus is on (MAGN led is off, toggle small/large focus
with DEN+ button in service mode) or a bucky or a cassette tunnel
attached.
Fig 4.6. Filament control board
3 Set the oscilloscope to 1V/div and 20ms/div. Set the trigger to app.
+1V / positive edge (storage mode).
4 Turn ON the unit. Set the unit to 27kV and 16-40 mAs (large focus).
5 Make an exposure and check the waveform. (see Fig. 2.28).
6 If the mA waveform contains either over- or undershoot at the start-
up, adjust from trimmer potentiometer R28 on the Filament control
board to obtain correct waveform.
NOTE!
The trimmer R28 is for LARGE FOCUS. For SMALL FOCUS, insert the
magnification cassette holder to the unit and adjust the preheat from
trimmer potentiometer R96. Be careful with preheat adjustment. Turn the
potentiometer little by little and check that scope figure will look as in
Figures 4.7, Correct preheat, 4.8, Preheat rises too fast "Overshoot" and
4.9, Preheat rises too slow.