Yamaha EMX 2000 Powered Mixer issue

[Phlox321]

Hi All

I have a yamaha emx 2000 powered mixer im trying to repeair.
the problem is that theres no sound output on the right channel. Left channel works fine.
Right channel has output when using the phono(headphone output) but not when going through the amplifier
the left peak meters work but not the right
the clipping light however does come on when gain is turned up same as left channel
What i have done so far is make sure that the supply voltages are fine, which they are
I found several cracked solder joints on the amplifier board which i have resoldered but made no difference
i replaced the stereo fader and 2 of the stereo input faders as it looked like the tracks on them had no carbon left ( tracks where white) and i got weird readings of like 180K ohm out of a 10K slide pot
that still made now difference.
there is a bit of sound coming from the output when everything is set to full volume and gain. i probed around some more, and so far ive just found a 100k resistor in the signal path of the right channel reading about 66k ohm
not sure if that could cause the issue

I have uploaded a service manual i found

any ideas?

[spiros.p]

Re: Yamaha EMX 2000 Powered Mixer issue

are you sure the muted cchanel is not blowed?take measurements and comppare the output devices with the good chanel see if voltage is the same to booth chanels.disconnect from mains and chek all the trans and resistors on output with dmm.chek if supply rails to the amp after the filter capacitors is present.

[Phlox321]

Re: Yamaha EMX 2000 Powered Mixer issue

Hi

I Made a contraption i read about on internet from someone else troubleshooting a mixer.Basically you inject a sine wave ( from phone or something else) and use a multimeter probe with one end grounded and capacitor added and the other end to poke around. The probes are connected to an amplifier with speakers. That way you can trace and hear where the signal gets "lost"

I thought at first it could have been the input section but thats fine, get sound on both channels.
I narrowed it down to the incoming signal to the master volume slider , or that region.

I took a chance and briged the working left channel 10k slide pot pin to the right channel and it worked. The VU lights up both channels and i get output to the amplifier on both channels. Not stereo , but i just checked to make sure the amplifier section wasn't blown and it is fine.

So looks like the signal is not getting to the master fader.
just cant pin point exactly where.
All the op-amps on left and right channel and master fader seem to be fine. get input 14v and output 14v, not sure how to test them really.
Only Wierd thing is i get around 30V +- to Op amp however in schematic its shows 15v+- (but the PSU outputs are fine)

The mixer seems to be working fine though.
Will check anyway to see where the 15v supply comes from and if it really is 15v +- or 30v +-