87
Set the lens voltages with the Peak Monitor and confirm the output voltages at the
feedthrough contacts on the IS CTRL-A PCB.
The normal output voltage lies in the range: set voltage ±5%.
LENS1, LENS2, LENS3, LENS4
If the output voltages do not lie within the set ranges, conduct the checks described in 2.
Checking the lens voltages for MAIN CTRL-A (page 60
).
3. Checking the filament currents
When a filament is on, the filament current can be determined from the following voltage
measurements. The relationship between the filament current and the voltage measured
with the tester + probe on CP16[FIL] and the - probe on CP18[EV] is as follows:
Filament current (A) = 2 x (V
CP16
– V
CP18
) max about 3.5A
If (V
CP16
– V
CP18
) = 1.4V, the filament current is 2.8A.
A filament discontinuity is detected and an error occurs if (V
CP16
– V
CP18
)≤approx. 0.6V, that
is if the filament current ≤approx. 1.2A.
The discontinuity in the filament can be easily confirmed by the following method.
Turn off the filament and measure the resistance between F1+ and F1-.
If resistance value ≤1Ω, the filament is normal.
Be aware of the polarity when measuring the resistance; correct measurement is only
possible by applying a positive voltage to F1+ and a negative voltage to F1-. If the polarity
is unknown, turn off the instrument power, remove IS CTRL-A to eliminate the influence of its
circuits and measure the resistance directly at the feedthrough terminals.
4. Checking the TRAP current control circuit
Set the emission current, turn the filament on, and measure the voltages at CP12[EMC],
CP13[TRP], and CP14[+10A].
If V
CP14
≠10V, the IS CTRL-A PCB is probably defective.
V
CP12
=set current(µA)/100
If emission current = 60µA, V
CP12
=0.6V.
Any abnormality suggests an incorrect D/A voltage from the CPU PCB.
V
CP12
=V
CP13
Any abnormality could be due to a filament discontinuity or incorrect installation.
5. Checking the emission voltage control circuit
This circuit generates the emission voltage (-10V to -200V).
Set the emission voltage, turn the filament on, and measure the voltages at CP15[EMV],
CP18[EV], and CP19[INV].
V
CP15
= 0.05 x set voltage (V)
If emission voltage = -70V, V
CP15
=-3.5V.
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