Hi, just picked up a DJM 700 for free, as the last owner didn't want to spend the time or money to fix it, I have no real experience with circuits boards, but I am a quick learner.

The problem with the mixer, theres no sound in the headphones are on the master out,

There is signal coming in on the input channel, but I have to turn the trim all the way up with the EQ to get a healthy signal, also when I switch between CD and Line on the channel it has no effect.

Video

Service Manual
https://elektrotanya.com/pioneer_djm-700-k-s_sm.pdf/download.html

 

I only can advise you to buy a new mixer https://houseandbeyond.org/best-dj-mixer/ I have Yamaha. It powers up quick and the connection is a nice screw attached version so it will be less likely to dislodge at random. The knobs and materials feel quite solid as well.

Thanks for the reply, but I already have a mixer, the pioneer was given to me for free, I was trying to fix it

 

Work from the output that is missing toward the source looking at the opamp ICs (4580). One or more are likely fried. This is a common failure in mixers in general. Either the power supply is interrupted or an IC has failed. Since the 4580 IC has 2 opamps in it, these are usually wired for L/R so a single IC failure will cause both channels to fail. Since you are losing both the master and the HP output, the failing IC is back far enough to be common to both. Once found, it should be easy to replace.