1604 mackie mixer question

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

da_ardvark

Well-known member
Joined
Jun 1, 2005
Messages
73
Location
New Matamoras OHIO
I have a little problem. Not sure if this will help narrow it down.

On Channel 1 the Mute led is shares function with overload detection. If i press the mute button, the led lights brightly. If I remove mute (this just started happening) the led is still lit, just not a bright.

The section of the schemo is

mackiemixer.jpg


The way I see it the red LED D104 has current flowing even without the mute switch. I'm suspecting the opamp U102A is not functioning properly.
The entire schemo is from gyrafs DIY page at the bottom. This is page 4 of the entire pdf.

Any comments of my sluthing????
 
Thanks for the feedback. It's kind of weird because this problem doesn't seem to cause any noise, and appears intermittant. Meaning at times the light will dim, and eventually go out at times.

I dont' think its the mute switch bucause it still functions properly, but I guess I can't rule it out entirely.

I think I'm going to leave well enough alone for the moment. I'll keep my eye on the problem and see if it worsens.

SSL, can you suggest substitues for U102 that would be better suited?

Thanks again
 
ESD damage through the LED or mute switch is possible. Also, check out any electrolytic caps just upstream of U102 - look for DC offsets in the various stages before this one to see if the problem comes from there. Also, an open-circuit 'pull-to-ground' resistor can create these problems as well.


-Dale
 

Latest posts

Back
Top