[sdiy] Mega Madness One

[Michael Ruberto]

John,

The problem isn't with the channels it seems to be limited to the master 
section. When I hear the distortion or level dropping it's only through the 
stereo output or the headphones. Signals from the any of the 4 sends are 
still normal. The thing that is annoying is the intermittent nature of the 
problem. The mixer will work fine for a few days and then the left or right 
output either becomes distorted, goes low or both low and distorted. It's 
either left or right but never both for some reason. I had the mixer on my 
bench all day yesterday and it worked fine until finally at 4am I checked it 
and found the left channel had dropped to half the level of the right.
At least I can now rule out any ground loop issues with it's normal place in 
the rack.

I am going to concentrate on the cards for the master section. There is a 
card for each master slider. The left master card is large and has alot of 
circuitry and the right card is smaller but has the main output connector 
going to the main out jacks. At this point I guess all I can do is attempt 
to reverse engineer them. All the ICs are SIPs with unfamiliar part numbers. 
I'll need to find out the pinouts of these.

M. A. Ruberto


>From: John Mahoney <jmahoney at gate.net>
>To: synth-diy at dropmix.xs4all.nl
>CC: "Michael Ruberto" <frankentron at hotmail.com>
>Subject: Re: [sdiy] Mega Madness One
>Date: Thu, 19 Oct 2006 19:25:33 -0400
>
>Thoughts:
>~ Test the backplane with just one channel card installed at a time.
>~ Try different slots.
>~ Test the channel cards in isolation, i.e. out of the backplane; use a 
>bench power supply or the mixer's supply (with long leads).
>--
>john
>

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