Sunday, December 23, 2012

Okay, I've known about the Otari XLR pin 3 hot configuration for quite some time now, but in practice I'd never run into a catastrophic failure because of it (that is to say, I was able to record and playback audio on the 2 track machine with little issue). Therefore, that bit of information sunk into the dusty corners of my mind where it was wholly ignored. Of course, all that free riding came to a screeching halt once the Autogram AC-8 was planted in the audio control trunk. See, in my wiring up the output I included unbalanced 1/4" phone plugs which were at one point normalled to the monitor amplifier.

So, when I connected the pin 3 hot, pin 2 ground configuration of the Otari to the pin 2 hot pin 3 neutral (actually earth referenced thanks to my inclusion of unbalanced 1/4") configuration of the mixer output, a whole lot of nothing happened. Nothing to the tune of even killing the monitor feed to the amplifier.

I had entered into really easy diagnostics, unplug cable = sound, plug it in = zilch. So, with a nod to the widely published pin 2/3 issue, I built a pair of XLR cables with pins 2 & 3 swapped. Solved. Of course, at this point I recall a few months previous while I am working on the basket case MX5050-8 and can't get any channel response out of it, which, at that point was a step backward but given the hard life the machine has had I place it closer to the parts bin. Why yes, I had been feeding it audio from the Autogram while failing to get signal, it was just prior to the monitor amp feed modification.

So, the 2/3 swap XLR cables worked here too. I was able to commit signal to tape and playback (on conventional XLR), and it sounded good. So, my options now are to make another 6 pin swap XLR cables, or just modify the machine to reflect pin 2 hot. Ready to cut traces and jumper stuff at board level, I was met with this magnificent sight. Build six special purpose cables, or simply rewire 16 connectors?

Easy decision.

I did this, from poor placement in a room (that gets gear hauled in and out of)...

..and this. Very preliminary internet searches do not favor the notion that this is an easy & standard current production off the shelf part. Since the switch still works I think I may drill a small pilot hole in the lever portion and turn down a bit of small bar stock to have an end pin, then epoxy the new arm in place. Worse case I'll still have to find a replacement switch.

Since this machine got hammered the interior finds include stuff like this, from the side panels.

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