I can't engage CAS with the front panel keys (with the YS1700, YS1500, YS1350, or YS1360).

Please check the following 3 points.

1. Is an input signal going to the cascade input terminal? If the cascade input terminal is open (IOP), the instrument is designed not to change from AUTO to CAS.
2. Is CMOD1=CAS or CMP set?
3. Is the operation mode AUTO? The instrument is designed not to move directly to CAS from MANUAL. Switch to AUTO using the A key, and then press the C key.

Note: To avoid changing modes unintentionally, the instrument is designed so that you have to hold down the C/A/M key for approximately 1 second or longer to switch modes.