peavey mark II mixer madness

[billbigrig]

Howdy,

I've got a peavey Mark II 16 channel mixer that works fine for a while, (1/2 to 1 hour), then starts going wiggy. All the leds blink on and off in synch with the ladder bars going up and down. It makes a honky noise, low pitch, in time with the ladder bars going up and down. I figure all this happens at about 2 to 4 hertz. Any ideas? Thanx.
Rig

[Enzo]

Check your power supply. All the ICs run on +15 and -15 if I recall. If one of the supply rails is getting soft and falling, that could cause such instability. Check when first turned on, then later when the symptom starts.