The "PROTECT" light indicator came on and now the

BAD NEG. 15V REGULATOR AND RELATED CAPS IN POWER SUPPLY.CAUSES UNIT TO GO INTO PROTECT. main supply caps and power transformer is gone. possible you'll have to trash. good success, meder's tv service

We can only guess at the cause without tearing into the unit. My educated guess is that either the cable to the color step motor has either come loose or a wire is broken in the cable. SInce the wires go through a flexure point, that MIGHT be where the problem is... the only way to tell is to do detailed troubleshooting of the unit.

That's the thing with today's electronic and why warranty length is so important. Where did you buy your keyboard? It's strange that they won't fix it if it's still under warranty. My Casio CTK-2100 came with 1 year free service and they fix one key that stopped function in few days. I'm pretty sure Yamaha has the same warranty length. You sometimes have to be very persistent with them though...

These seem to be tempermental. I would look for radio frequency interference from nearby transmitter leaking into your guitar cable or mic cable that puts this on the ragged edge of feedback. DO NOT boost highs with the EQ... You can get supersonic feedback that you can't hear, but puts the amp into limiting. Any audio input can start the feedback. These amps are VERY hard to work on due to the packaging. A lot of people have smoked their units and then require repairing.

The Efx 12 has two outputs monitor out as well as mix out ( XLR sockets ). If the level bars are moving its an indication that the mixer is working. Have you tried headphones out as well as monitor out.
What is your amplifier and speaker setup- you have not mentioned it at all.
Even if any PFL switch is on you won't get sound out of the speakers.
PFL stands for Post Fade Listen and when any of the 12 channel PFL switch is on only the headphone out put will work.

Don't mess with it and risk voiding your warranty. These are a servoed speaker and there is a problem with the feedback in it. Exercise your warranty immediately.

Either one of the amps or the power supply has blown. The protect light means the power supply has been shut down due to overcurrent. Take unit in for repair. These are hard to work on due to packaging.

Likely there is either a failure in one of the power amps or the power supply. The protect means excess current is being sensed.

You need to take in for repair... these are really hard to work on due to the packaging.

This indicates either one or more of the amps have a failure OR the power supply is being overloaded which is usually also caused by failure in the amplifier.

Occasionally a power supply failure causes this problem as well.

Due to the way these are packaged, they are a real pain to work on for repairing.