Service manual CAN NOT TURN ON WHEN ADAPTER PLUG IN

wrong plug

If you turn it over, you will see the battery compartment. It runs on 6 AA batteries. Here's a link to the manual. Instructions are on page 13.
http://support.casio.com/pdf/008/ctk_496_700_e.pdf

Here is a link to an online manual, it appears that you may can download it. I hope this helps you.

Check the polarity on the adapter plug. It must correspond to the diagram on the keyboard . If it's reversed, just cut and resolder the cable that connects to the keyboard.

My 3500 also has a similar problem. It only switches on if I plug the power and immediately press start . If I wait a few seconds it won't start.

U.S and Canada: 20 VAC, 60 Hz Adapter: PS093B-20
Japan: 00 VAC, 50/60 Hz Adapter: PS093B-00
Europe: 230 VAC, 50 Hz Adapter: PS093B-230
UK: 240 VAC, 50 Hz Adapter: PS093B-240

Power adapter requirement straight from the user manual. I am sure you are aware that a simple plug adapter in a tourist shop does nothing to convert 120v US to 240v AUS. Note you unit does not like temperatures above 40C. And you can get that in Australia.

Bear in mind the timezone difference if you try Digitech support in the US.

DIGITECH VOCALIST LIVE 4 Owner Manual Page 36

From the user's manual:

The Check light lights when the effect is on. It ALSO is a battery indicator and when it gets dim, you need to replace the battery if you are not using an adapter.

If it won't go OFF when you try to turn it off, then the switch has probably failed or wiring to it has failed. In this case, service is required.

Check battery direction. Also if the unit can use a power adapter, sometimes the contact in the connector for the adapter that connects the battery when the adapter plug is out fails to contact and connect the battery.

You may have damaged the data on the memory card. If you have no display at all carefully read page 125 of your manual.If it doesn't display with the adapter plugged in try new batteries. If it still doesn't display anything, contact the dealer you bought it from or try contacting Roland. This site should help:http://www.rolandus.com/support/service_centers/

First thing is to check your power adapter. It should be producing something over 9 volts AC. Also check that this connector is seated.
Also check the adapter is getting power. Some have had their adapter in a plug strip and the weight of the adapter has turned off the switch on the strip... silly but it happens.

If you know how to use a multimeter then I suggest you measure the voltage from your wall adapter plug that you plug into the keyboard. If that has approx. 9Vdc, then take a look at d151 on the power supply board. See if it is passing voltage. Voltage should pass only 1 way. If you have voltage on one side but not the other then the diode it is open and needs replaced. You can find the diode designator on the board next to the diode.