Author Topic: Mini/Main switching not working  (Read 108 times)

jchestek

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Mini/Main switching not working
« on: November 01, 2018, 03:39:23 PM »
I have a bit of a puzzle.

I'm working on an 8000G; the Mini LS switch doesn't function (it used to, but now, no).  The monitor signal always passes to the mains.

The switch itself seems to be operating, I can see it toggle from +11 to +18V when depressed.  From the system logic diagram it appears that it should connect to pin 43  ("Mini switch") of the "22" card, but I don't see the voltage change there, that pin is always at +11V.  If I apply +18V to that point, the monitor signal goes to the minis, as it should.

Seems simple enough, broken wire between those two points, right?

The problem is that the "Mini" switch is a momentary switch on this console.  And when I release the +18V from pin 43, the monitor signal goes back to the mains. 

Because the switch is momentary, there must be a flip-flop somewhere to latch back and forth between the Mains and Minis, right?

I can't find it on the schematics for the life of me.

The console has what looks like a standard "22" card;  in the "24" card slot is a "274" card.  There's a factory installed jumper wire between pin 43 on the 22 card and pin 43 on the 274 card ("Mini switch" input on both cards)

What piece of the puzzle am I missing?

This WAS a film mixing console, but it doesn't have the Monitor Input and Format (SL592) module.  I don't know what that implies, and I suspect that we're missing some pieces of documentation.

Jeff

amillar

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Re: Mini/Main switching not working
« Reply #1 on: November 09, 2018, 10:29:29 AM »
I did have a quick look at this but I am baffled - but I don't have a 8k manual (and don't know much about how they fudged the monitoring on it).

 :(

Andy
co-designer and project manager G series analogue 1987
channel strip designer J series 1992-93
design "caretaker" 4000/6000 1985-93
analogue team leader ARC/Bertha 1988-92