331C and 331 power supply differences
The 331C have a different AC power supply than the older 331's, they cannot be mixed.
The 331C uses a 12VDC adapter and the 331 uses a 5VDC adapter.
The pins of the adapters are polarized differently.
331C uses the SE30-277 power supply only
earlier 331 used the SE30-45 only
***Use of the wrong AC Adapter will damage an instrument.