Wierd mixer problem..

Optical · 15th February 2005, 08:58 AM

I have a faiirly cheap mixing desk, full of opamps..

The problem is the left side of the master channel cuts out completely when the level is low.. When the level is increased to around 0dB theres a slight popping sound and the channel springs back to life..

so basically i have to keep my master level high or it cuts out..
It seems to be soley electronic as opposed to a mechanical fault..

has anyone heard of opamps cutting out at low levels?

pinkmouse · 15th February 2005, 09:26 AM

Sounds like a faulty volume pot to me. Give it a blast with some contact cleaner, or swap it out.

Optical · 15th February 2005, 09:56 AM

Well im pretty sure its not mechanical as it is completely unrelated to where the fader position is..
But i'll give it a go, nothing to lose..

Netlist · 15th February 2005, 10:02 AM

Bad solderings?
What brand and type is it?

/Hugo

Optical · 15th February 2005, 10:08 AM

heh, Its behringer..
If the output level stays above 0dB it always works fine..
could be a dry solder joint, but you'd expect it to cut in and out when you jiggled things..

faulty cap perhaps? I really have no idea.. its got me stumped..

Netlist · 15th February 2005, 10:19 AM

Quote:

Originally posted by Optical
when you jiggled things..

Yes, in many cases you are correct but a thorough checking will rule this out.
I usually inject a sine wave in one of the inputs and try to follow the signal path with a scope.
I could be a faulty cap but this is about the last thing I would look for.

/Hugo

pinkmouse · 15th February 2005, 10:32 AM

Quote:

Originally posted by Netlist
I could be a faulty cap but this is about the last thing I would look for.

I agree, my money is still on the pot. Those sypmtoms sound exactly like something liquid has been spilt over the mixer.

al/ remembers a Janet Jackson gig where a 2 litre carton of orange juice sailed majestically out of the crowd and landed right on the 48 channel Amek monitor desk.

Frank Berry · 15th February 2005, 10:36 AM

What Behringer model?
Does it use VCA's for faders?

Centauri · 15th February 2005, 11:20 AM

Quote:

Originally posted by Optical
heh, Its behringer..
If the output level stays above 0dB it always works fine..
could be a dry solder joint, but you'd expect it to cut in and out when you jiggled things..

faulty cap perhaps? I really have no idea.. its got me stumped..

Can tell you exactly what it is - ribbon cable from mainboard to output jack board. The cable conductors are too small for the IDC connectors - replace cable with some decent stuff.

Very common - other ribbons quite oftencause channels to drop out.

Cheers
Graeme

Optical · 16th February 2005, 01:26 AM

Im not quite sure what you mean by the ribbon cable being too small and causing the drop-out.. you mean physically too small? or electrically?

ok, well i guess i'll be pulling it all apart then.. the scrutinising with the scope thing is what i was planning on, not particularly looking foward to it though..

oh, it's an MX1604 for those interested. its never had anything split on it, does get a little dusty and the cat is always around

15th February 2005, 08:58 AM	#1
Optical diyAudio Member Join Date: Nov 2002 Location: Auckland, New Zealand	Wierd mixer problem.. I have a faiirly cheap mixing desk, full of opamps.. The problem is the left side of the master channel cuts out completely when the level is low.. When the level is increased to around 0dB theres a slight popping sound and the channel springs back to life.. so basically i have to keep my master level high or it cuts out.. It seems to be soley electronic as opposed to a mechanical fault.. has anyone heard of opamps cutting out at low levels?

15th February 2005, 09:26 AM	#2
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Sounds like a faulty volume pot to me. Give it a blast with some contact cleaner, or swap it out. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

15th February 2005, 10:36 AM	#8
Frank Berry diyAudio Member Join Date: Sep 2003 Location: Midland, Michigan	What Behringer model? Does it use VCA's for faders? __________________ Frank

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15th February 2005, 09:56 AM	#3
Optical diyAudio Member Join Date: Nov 2002 Location: Auckland, New Zealand	Well im pretty sure its not mechanical as it is completely unrelated to where the fader position is.. But i'll give it a go, nothing to lose..

15th February 2005, 10:02 AM	#4
Netlist diyAudio Moderator Join Date: Jan 2003	Bad solderings? What brand and type is it? /Hugo

15th February 2005, 10:08 AM	#5
Optical diyAudio Member Join Date: Nov 2002 Location: Auckland, New Zealand	heh, Its behringer.. If the output level stays above 0dB it always works fine.. could be a dry solder joint, but you'd expect it to cut in and out when you jiggled things.. faulty cap perhaps? I really have no idea.. its got me stumped..

16th February 2005, 01:26 AM	#10
Optical diyAudio Member Join Date: Nov 2002 Location: Auckland, New Zealand	Im not quite sure what you mean by the ribbon cable being too small and causing the drop-out.. you mean physically too small? or electrically? ok, well i guess i'll be pulling it all apart then.. the scrutinising with the scope thing is what i was planning on, not particularly looking foward to it though.. oh, it's an MX1604 for those interested. its never had anything split on it, does get a little dusty and the cat is always around

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