Broadcast Switch Mod

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

Moderator: brianroth

Broadcast Switch Mod

Postby MCI Chris » Sun Feb 28, 2010 6:03 pm

Hey everyone,

Chris here from Tulsa.

As you all know Brian Roth from this site has been down a few times and is totally re working my 636 to bring her back to life. its going really well and we have gotten alot done.

Brian did a really cool mod which I never seen before. We had several channels that had shorts and were stuck in "solo". Therefor it wouldnt pass audio, etc. Well he fixed them up no problem and then modded the broadcast switch to light up red when or if a channel is in solo. The actual broadcast switch was bypassed and he jumped a cable from the LED to the master relay for the soloing. YOu will have to ask him for more details, but I thought it was great.

Most console's have a big red light or something showing in the master that you are in some type of solo, well the MCI's dont really do that, since the broadcast button is totally pointless in this application.

Anyway I thought it was pretty cool.

MCI Chris
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Re: Broadcast Switch Mod

Postby brianroth » Mon Mar 01, 2010 3:47 am

I see that Chris "beat me to the punch", so to speak!

As he mentioned, the "Broadcast" switch was installed on the Monitor module of every JH-600. However, unless the "broadcast option" I/O modules were ordered, that switch and LED do nothing at all.

There is a 3K6 current limiting resistor in series with the LED. So, I unsoldered the end of the resistor that does NOT connect to the LED and ran a jumper from that back to pin 1 of the LM-324 chip which does the solo switching logic. There is a resistor by that IC which ties to pin 1, so it was an easy mod done on the component side of the circuit board.


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