mci jh 428b vca automation info sought

In the late 70's, over half of the records in Billboard's Top 200 were recorded and/or mixed using MCI equipment.

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mci jh 428b vca automation info sought

Postby rob » Mon Nov 29, 2010 1:54 pm

Hello folks,

Just wondering if anyone has any diagrams or info on the automation board which was fitted to some of the 428b desks. It slots doen the side of the fader, & has one of those dreadfully noisy black cannister dbx vca's on it !

I'm looking at a channel strip at the moment that has this fitted, although I'm told the vca has been disabled. I just wanted to get my head round this because I can't really see any modifications to this board, & it looks stock to me.

Thanks in advance.
regards Rob
rob
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Re: mci jh 428b vca automation info sought

Postby porkyc » Tue Nov 30, 2010 7:52 am

There might just be a jumper wire on the 26-way ribbon header to link the VCA TO auto to the VCA FROM auto. The console was designed to have the automation running all the time and the muting/soloing/VCA grouping was done by the automation. When the automation packed up, and there was no saving it, so a means of effectively bypassing the auto had to be found. On non-auto 500 consoles this jumper was a molex on the motherboard, but because the 400/600 were designed with auto on all the time, there was no jumper facility.
The VCA itself has not been bypassed because the fader law is not stock log audio, it is a softer lin/log law. This combined with the log/anti-log characteristics of the dBx gave you the correct log law.
PC
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Re: mci jh 428b vca automation info sought

Postby rob » Fri Dec 03, 2010 6:27 pm

If anyone has a copy of the srvice manual for the JH 428 vca automation, or any diagrams of the vca board, I could really use them ?
regards Rob
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Joined: Fri Jan 11, 2008 8:35 am
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