See attached video for basic valve operation and adjustment.
Below and attached is a transcripts of the video.
This video covers the Siemens SQM40 proportioning gas control valve as used on Despatch gas fired ovens.
The valve takes a 4 to 20 milliamp signal from the temperature control and modulates the gas flow between low fire and high fire to maintain the set oven temperature. 4 to 20 milliamp signal is connected to terminal block X1, terminals 1 + and 2 -.
The valve has an indicator showing the position of the valve. This valve is 30 degrees open.
There are 3 settings that can be adjusted on the valve.
Low fire, High fire, and Ignition.
Each setting corresponds to a colored cam on the valve.
The red cam is used for high fire and is typically set to 90 degrees.
The black cam is used for low fire and is set as low as possible while still maintaining a good flame signal. Usually, 0 to 10 degrees.
The green cam is used for ignition and is set at a reliable burner ignition level. Usually around 30 degrees.
The Yellow, Cam is set just under the green cam.
The Orange, and Blue cams are auxiliary switches that typically are not used on Despatch Ovens.
There is a relay that switches the valve between ignition and control operation.
For Ignition, 120 volt power is applied to terminal block X2 terminal 4.
After the burner ignites and flame is established, power is removed from x2 terminal 4 and power is applied to terminal block X2 terminal 9.
In control mode when the valve receives a 4-milliamp signal from the control, the valve will move to the black low fire cam setting.
In control mode when the valve receives a 20-milliamp signal from the control, the valve will move to the red high fire cam setting.
There is a release button that de-couples the motor from the valve.
Pressing the release button allows you to manually turn the valve to any position you want. It also takes the pressure off the cams to make them easier to adjust.
To review.
The red cam is set for the high fire position.
The black cam is set for the low fire position.
and the green cam is set for the burner ignition position.
This completes the training on the SQM40 gas control valve.
For additional information refer to the oven manual, or Siemens Technical Instructions.