Ulvac EGL-206M Instruction Manual page 54

Trouble symptom
14. The evaporation rate
decreases. No change in the
input power and beam spot
size. The vacuum level is
normal.
15. The evaporation rate
decreases and is unstable.
Apparently there is no
change in the beam spot
size.
16. The beam spot size is too
large.
17. Distorted beam spot or no
symmetrical sweep on both
right and left sides.
Possible cause
D. Poor contact of the filament cable
or filament lead.
E. The hearth is contaminated.
Or evaporant is not sufficiently
degassed.
A. Incorrect dimensions of the emitter
assembly.
B. Deformation of the filament
(filament life expiring )
A. Oxidization of evaporant.
B. Increased ripple in the high voltage
(5% p-p or more)
A. High voltage sweep
B. Decreased high voltage
C. Excessive ripple in the high voltage. a. See item 15.
D. Incorrect dimensions of the emitter
assembly
A. Non uniform magnetic flux
distribution.
SECTION 7
a. Check terminals to see if they are tight. If loose, retighten
them.
a. Clean the hearth.
b. Degass evaporant sufficiently.
c. Change evaporant with a high purity evaporant.
a. Check the dimensions against Figure 5.1.
a. Change the filament.
a. Change evaporant.
a. Check if oscillation occurs in the high voltage circuit of the
power supply. See its instruction manual.
b. It is likely that radio frequency noise or thyristor noise is
superimposed on the 3-phase power line of the EB gun power
supply.
Check the waveform of the input voltage on an oscilloscope.
If noise is observed, insert a line filter.
a. Lower the sweep level.
a. Expansion in the Y-axis direction can be supressed by using a
shorter trimming piece.
a. Check the dimensions against Figure 5.1.
a. Check if there is any ferromagnetic material near the unit.
b. Check if there is any device that produces a magnetic flux.
44
Corrective action