Need help diagnosing bad mixer channel

[Brian]

I have a little Yamaha 8 channel mixer, about 3 years old, that I use
for live performances, and channel 1 is malfunctioning. I'm hoping
this is something I might be able to repair myself, I don't want to
spend a couple hundred bucks having a $300 mixer repaired. I also
don't want to buy another mixer. I'm fairly handy with a soldering
iron, and have a cheap multimeter and rudimentary electronics
knowledge. I use this mixer frequently and I'm hoping I can perform a
satisfactory homebrewed repair to get it back in action.

The symptoms: The input and preamp seem to be working, but there is no
signal getting to the main outs from this channel. I can hook up a mic
or instrument and see the input level on the LED meter, but when I
un-mute the channel there is no sound from the main outs. I havn't
tried to see if the aux sends are getting a signal from it yet.
The gain pot works but seems 'weak' compared to the other channels, ie
I have to turn the preamp gain up pretty high on this channel to see
the same levels on the meter as a much lower gain on the other
channels.
I don't know if this could be as simple as a connection came
unsoldered inside, or if an internal component might actually need
replacing. What are some possibilities, and what non-obvious things
should I look for when I open it up? Things I can test with the
multimeter?

thanks,
Brian

[No Name]

"Brian" > wrote in message
...
>I have a little Yamaha 8 channel mixer, about 3 years old, that I use
> for live performances, and channel 1 is malfunctioning. I'm hoping
> this is something I might be able to repair myself, I don't want to
> spend a couple hundred bucks having a $300 mixer repaired. I also
> don't want to buy another mixer. I'm fairly handy with a soldering
> iron, and have a cheap multimeter and rudimentary electronics
> knowledge. I use this mixer frequently and I'm hoping I can perform a
> satisfactory homebrewed repair to get it back in action.
>
> The symptoms: The input and preamp seem to be working, but there is no
> signal getting to the main outs from this channel. I can hook up a mic
> or instrument and see the input level on the LED meter, but when I
> un-mute the channel there is no sound from the main outs. I havn't
> tried to see if the aux sends are getting a signal from it yet.
> The gain pot works but seems 'weak' compared to the other channels, ie
> I have to turn the preamp gain up pretty high on this channel to see
> the same levels on the meter as a much lower gain on the other
> channels.
> I don't know if this could be as simple as a connection came
> unsoldered inside, or if an internal component might actually need
> replacing. What are some possibilities, and what non-obvious things
> should I look for when I open it up? Things I can test with the
> multimeter?
>
> thanks,
> Brian

Brian you need to send a steady test signal into your mixer to evaluate the
gain diffrence issue
I am not a tech but I will bet you find your board is heavily constructed
with surface mount technology
not impossible to repair but it takes a higher level of skill than
most"people handy with a iron" can muster

also you need to test the aux send to determine where the signal is bad
a good place to start is cleaning the insert jacks
they are switching jacks and dirt/odidation there can cause problems similar
to what your describing
but again I am NOT a bench tech, and my info is base on what this NOT A
BENCH tech has picked up randomly over the years
George

[Brian]

>
>Brian you need to send a steady test signal into your mixer to evaluate the
>gain diffrence issue
>I am not a tech but I will bet you find your board is heavily constructed
>with surface mount technology
>not impossible to repair but it takes a higher level of skill than
>most"people handy with a iron" can muster
>
>also you need to test the aux send to determine where the signal is bad
>a good place to start is cleaning the insert jacks
>they are switching jacks and dirt/odidation there can cause problems similar
>to what your describing
>but again I am NOT a bench tech, and my info is base on what this NOT A
>BENCH tech has picked up randomly over the years
>George
>

thanks for the feedback. dirt in the insert jack or elsewhere is highy
probable considering the working conditions this mixer typically
endures :). I'll check that out. Maybe it just needs a good cleaning.

By surface mount, you mean the components are probably all attached to
a single circuit board? You're right, I probably can't replace
anything myself if that's the case.

[Gareth Magennis]

"Brian" > wrote in message
...
>I have a little Yamaha 8 channel mixer, about 3 years old, that I use
> for live performances, and channel 1 is malfunctioning. I'm hoping
> this is something I might be able to repair myself, I don't want to
> spend a couple hundred bucks having a $300 mixer repaired. I also
> don't want to buy another mixer. I'm fairly handy with a soldering
> iron, and have a cheap multimeter and rudimentary electronics
> knowledge. I use this mixer frequently and I'm hoping I can perform a
> satisfactory homebrewed repair to get it back in action.
>
> The symptoms: The input and preamp seem to be working, but there is no
> signal getting to the main outs from this channel. I can hook up a mic
> or instrument and see the input level on the LED meter, but when I
> un-mute the channel there is no sound from the main outs. I havn't
> tried to see if the aux sends are getting a signal from it yet.
> The gain pot works but seems 'weak' compared to the other channels, ie
> I have to turn the preamp gain up pretty high on this channel to see
> the same levels on the meter as a much lower gain on the other
> channels.
> I don't know if this could be as simple as a connection came
> unsoldered inside, or if an internal component might actually need
> replacing. What are some possibilities, and what non-obvious things
> should I look for when I open it up? Things I can test with the
> multimeter?
>
> thanks,
> Brian


If the mixer has insert jack sockets on each channel, it is probably dirty
and causing an intermittent signal. Try plugging and unplugging a jack plug
a few times and the dirty contact may clean itself. Next you could try all
the switches that cut or send the signal to the main outs such as mute,
route to main or groups etc. If any are dirty, operating them a few times,
as with the inserts, may clean the contacts.

If this doesn't work, and the channels do have insert sockets, try plugging
a signal straight into the insert socket. You may have to only push it in
one click as it is a stereo jack socket. If all is well (compare with
another channel) then the problem is somewhere between the input sockets and
the insert socket.




Gareth.

[Brian]

>
>
>If the mixer has insert jack sockets on each channel, it is probably dirty
>and causing an intermittent signal. Try plugging and unplugging a jack plug
>a few times and the dirty contact may clean itself. Next you could try all
>the switches that cut or send the signal to the main outs such as mute,
>route to main or groups etc. If any are dirty, operating them a few times,
>as with the inserts, may clean the contacts.
>
>If this doesn't work, and the channels do have insert sockets, try plugging
>a signal straight into the insert socket. You may have to only push it in
>one click as it is a stereo jack socket. If all is well (compare with
>another channel) then the problem is somewhere between the input sockets and
>the insert socket.
>
>
>
>
>Gareth.

Each of the 6 XLR channels does have an insert jack, including the bad
channel. From the responses, sounds like this is a likely culprit!
I'll check it out this evening.
>
>

[Gareth Magennis]

If all is well (compare with
> another channel) then the problem is somewhere between the input sockets
> and the insert socket.


If not, probably the fader or its wiring.

[Mike Rivers]

On Mar 22, 8:52 am, Brian > wrote:

> I don't know if this could be as simple as a connection came
> unsoldered inside, or if an internal component might actually need
> replacing. What are some possibilities, and what non-obvious things
> should I look for when I open it up? Things I can test with the
> multimeter?

All of those are possibilities, but a multimeter won't tell you very
much. The best troubleshooting tool (along with a schematic and the
knowledge to read it, of course) is an oscilloscope so you can put in
a steady sine wave signal and see how it changes as you move through
the channel signal path. Next best is a headphone amplifier and a
probe on the input so you can at least listen to tell if the signal
drops significantly when it shouldn't or if it becomes distorted at
some point.

And while you're probing around in there, maybe you'll stumble on a
loose connector or bad solder joint.