Why do i get a loud hum when i use turntables but not cd decks on my behringer djx750?

SOURCE: left output from one of my turntables cuts out regularly leaving a hum

No, the issue is either with the RCA cables or the tonearm. You might also want to check your cartridge and headshell connection. Make sure the contacts are nice and clean, and securely on the headshell. Have you tried swapping out your turntables? Take the left turntable, and put it on the right channel's input, and vice-versa? This will tell help isolate the issue. If the problem just moves, then we know it's not your mixer. If the problem remains on the same side, then you know there is something wrong with your mixer.

If the problem moves, then you can safely say it's your turntable with the issue. The STR8-30's aren't the greatest quality, so it's also possible that you have a faulty tonearm or RCA cables.

Hope this helps.

DJPROAUDIO
TWEAK AV LAB

SOURCE: Numark cdmix2 bpm counter

The CD Mix-1 had a "tap" button for the BPM counter, but the CD Mix-2 doesn't have the BPM feature. They both use the same LCD screens, though, so while you can see the "BPM" on the screen, it is not a function that is included. Why Numark did this is beyond me. I had a CD Mix-1, and while primitive, the BPM 'tap" button worked just fine.

SOURCE: BPM counter Numark CD-Mix 2

The CD Mix-1 had a "tap" button for the BPM counter, but the CD Mix-2 doesn't have the BPM feature. They both use the same LCD screens, though, so while you can see the "BPM" on the screen, it is not a function that is included. Why Numark did this is beyond me. I had a CD Mix-1, and while primitive, the BPM 'tap" button worked just fine.

SOURCE: CDJ800mk2

better take it to the dealer and get it changed since you have the warranty for it.

SOURCE: loud humming noise

If all of your door switches check out, replace the magnatron, capacitor, and diodes.