Shimadzu GCMS-QP2010 Series, Service Manual, Page: 104 / 168

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2. Checking the tuning
Use the tool software to check if the tuning is correct.
If tuning is correct (if the screen value valley can be confirmed by turning the core trimmer) it
is safe to judge that the circuits related to the RF power-supply high frequency (V) are
normal.
Conversely, if the tuning is not correct, the high-frequency-related circuits are defective or
the load is abnormal. Check the wiring around the QP rod.
Explanation
When the RF value is set with the tool software, the set voltage is output from CP8[V-RF]
(approximately 4.58V at m/z500).
1.05MHz is output when the RF output turns on, and a sine wave is output from CP13 to
create a proportional relationship between the set value and high-frequency wave detection
feedback value CP4[FB]. If the proportional relationship is not maintained, output CP16
goes out of range and an error signal is output.
CP13 is connected to the primary side of the coil and outputs an approximately 50 to 70V
P-P
sine wave at a setting of m/z500. The value monitored by the tool software is the value
read from CP14.
3. Checking the U voltage
If the check of the tuning indicated that the V voltage is correct, next check the U voltage.
When the main rod bias is set to m/z500 at -3.5V, check that the CP10[U1] and CP9[U2]
values are approximately 204V at the positive side and approximately -210V at the negative
side. It is recommended to use the Tuning Check window to make the RF setting (because
RF scanning is conducted from other windows). The RF setting changes due to switching
the positive and negative polarity (A or B) and due to the ionization mode (positive or
negative).
Explanation
As the U voltage is generated from a feedback output, if the U voltage is correct, then the V
voltage must also be correct. (This provides reconfirmation.) RF GENE-A outputs no
error signal if the U voltage is not output. Consequently, the U voltage output should be
suspected if no peaks are obtained but the RF power supply outputs no error.
4. Adjusting the trimmers