Automatic shut down?

If the mixer output shuts down as you describe, some part is over heating and once it cools down you can turn it back until it happens again. This will not be user serviceable. Here is the link to Peavey Support who can provide a service center contact and schematics.
peavey com

Maybe an open ground somewhere or something needs shielded.

It is a definite pickup grounding issue causing hum/"buzz" which diminishes when touching strings. Check the impedance of cable jack inputs and cable which should be 1/4"mono input/output jacks) . A personal preference but effective is to NOT run guitar direct into mixer but through an external amp w/ a headphone out jack . Noise gating/preamp filter also will help eliminate the "buzz"/noise from pickups. It is unfortunately the nature of the "electro-magnetic" beast when it comes to electric guitar pickups .Hope this helps.

Is the number on the effects display still flashing? Can you select effects or is that section dead now? I've had occasions with my Behringer mixers where a bad ground or otherwise improper power supply seems to cause issues with the effects section but the board seems otherwise functional. It has definitely had me scratching my head a few times and is worth investigating.

yes,, Pre means before powered or amplified ,, so yes you can do this to a powered mixer, just be sure that the power is off before making any connections,, without the ground of the rca cable touching , the blast to the speakers can invert the cone !!

so its a buzzing noise. are your turntables grounded? some dont have to be. the buzzing could be several things feedback from something around you or the mixer is buzzing cause of to much power. just mess around w stuff your not gonna break it. and what i mean about that is more wires check wires. dont preform open heart surgery on your equptment. sometimes the buzzing means the faders are going i own 3 vestax mixers and on my pmc 17a right before the faders went i had massive buzzing sound.

You are looking at the WRONG end of the guitar cable. You have a VERY unsafe guitar amplifier OR the mixer that is connected to that mic has an UNSAFE grounding condition.

If your guitar amp is an old one that has a two wire cord and a switch you change to reduce hum, take it in to have a three wire power cord installed IMMEDIATELY. Only plug into grounded receptacles. This is needed to reduce electrical noise and hum but MORE importantly is personel safety.

If the problem is with the mixer and the electrical service to the mixer, better get a professional in to analyze the problem before somebody is injured.

AS A START do this: VERIFY that ALL interconnected equipment INCLUDING your guitar amp iis powered from the same source or receptacle. This includes the venue power amps, mixer, any CD players, etc. Professionals run power back from the stage source to the mixer alongside their snake to avoid just the problem you are seeing. When they need more power at a venue, a power distribution box is used that conditions the building power and insures grounding.

Did you have this speaker AND the device that drives it connected to the same power source? If run by a mixer you MUST run a power extension from the same place your powered speakers are powered to the mixer. Ground bounce due to wiring in a building can destroy input circuits due to ground faults and static discharges. ALWAYS use balanced lines either XLR or TRS cables to interconnect the audio.

Also verify your power receptacle is properly wired. Carry one of those plugs with the indicators showing receptacle is wired correctly. Don't plug anything in until you verify it. Some venues are noted as having bad electical service.

Let your speaker sit for a minute and repower it... sometimes they have a lockout that takes time to reset.

That time lag would indicate a thermal problem.

Likely the power supply is a switching type that has some three terminal regulators after it such as 7805, 7815, 7915.

These have thermal protection in them and one may be shutting down.

Use circuit cooler to isolate the part that is shutting down.