Channel 4 Dead please help

[Mikey8511]

hi guys
please can you help me so i finally got to install my D8b into my studio 2 nite everything was going peechy until i started to test the channels and number 4 is dead nothing in or out but all the others are working fine
the fader works fine on channel 4 as dose the v-pot at first i thought it could be my snake so i plugged direct in the back of the desk on both the mic/line and still nothing any ideas
cheers
mike

[Mikey8511]

just to add channel 4 is putting out 48v phantom anyone got any ideas?

[Petersueco]

www.mackie.com 2011-10-27 23-51-2.png (Array KiB) Viewed 2010 times

Try the the 48v switches at the top.

Take also a look and check for inserted plug-ins in channel 4.

Another thing to try is to reset your Startup Session:

- Flush all your Startup Session files down the toilet.
- Press Control+1 on the keyboard to enter the Setup window. Click on the General tab and make sure "Load Last Session on power-up" is not checked.
- Reboot.

The d8b will create a new Startup Session file with the default settings.

Peter Holmquist.

[FrankH]

....and if none of that works:

(1) Try exercising the Mic/Line switch vigorously.
(2) Try exercising the channel's 48v switch.
(3) Try exercising the channels gain Trimpot vigorously.
(4) And finally....plug a TRS plug into channel 4's Insert and short the Tip to the Ring to see if the channel comes back.

And make sure you have a bonafide signal present in your "direct" signal test cables....by confirming that the test signal(s) show up in neighboring channels.

[High C Double G]

d8b people are cool, huh Mikey.

I got nothing to add but I am a proud d8b owner.

Is there a Wiki page on the d8b yet?

[Axeman098]

This was how I snagged mine so cheap. The guy told me he had 2 channels out on the board. No signal, etc. After a little digging around, I traced it back to the Phantom Power switches. Pushed 2 buttons, and got both channels back

[synthjoe]

You might also want to check by injecting signal via the insert jack, if all the above fails. That point is one opamp closer to the A/D converter. A/D is probably fine as it works on channel 3, I understand (3 & 4 are handled by the same A/D chip).

[Axeman098]

My first guess is a button or setting on the board. Like I said, the guy that sold me mine thought he had two bad channels, and it turned out to be the Phantom power switches. The sad part was, you could tell he'd given up on them for some time, because the channels had tape markers that looked like they'd been on it for a decade, and both of the channels in question were marked BAD on the tape. As wonderful as the D8B, and any digital Mixer for that matter, is....they do come with a somewhat overwhelming learning curve when you first begin to use them. On something as complex as the D8B, I've found from my own experience that it is EASY to miss a tiny thing like a button position, or mode setting when something isnt right. since your problem is with channel 4, (and I believe SynthJoe is correct about the A/D chip), then I would focus on anything and everthing associated with that channel and it's buttons, routing assignments, etc. *I* would go about making channel 4 LOOK like all the other chanels around it. Faders, pans, buttons, vpots...etc. Whenever I have a mixer channel with a sound issue, especially live, I try to visually determine what might be different on that channel as compared to the others, what buttons are pushed etc. I can usually find a discrepency quickly IF it's something I have set incorrectly using this type of approach. If after visual inspection I can still not detect an audio signal, now it's time to look at other issues.

Just a hunch, but try turning off the phantom power. Turn the board off....set Phantom power to off (OR match however you have the others around it set), then power the board back on. Some mixers are VERY finicky about how you manage phantom power and when you can or annot turn it on or off. I don't remember exactly what the rules is, but I remember on some, that messing with the 48v power while the board is on is not a good thing, and in some cases COULD damage the input. Someone else please chime in on that, as I don't use Phantom power much, so my memory on that is sketchy...

In this case, if all other options fail, I would then consider opening up the underside of the console and checking your ribbon cables. The D8B is notorious for loose ribbon connectors. Check the ones on the Anolog I/O board especially. I'd be very surprised if the channel has actually "died", as usually it's more than one when they actually fail. Digital Mixers usually group their Anolog I/O into as few PCB's as possible, so if there WERE a physical equipment failure, you'd likely have SEVERAL channels out....not just one. Let us know how it goes.

[synthjoe]

In this case, if all other options fail, I would then consider opening up the underside of the console and checking your ribbon cables.

Yep, if nothing else helps the infamous ribbon cable procedure is a good one to try before grabbing the soldering iron.

[Mikey8511]

hey guys your all a big help I've managed to solve my problem i was up till 2am friday nite with my desk in bits i downloaded the scematics and traced the problem back to a dry solder joint and a dud resistor near J4 on the AI/O board put it all back now and it works a treat if anything Channel 4 sounds clearer and cleaner than the rest so in the next few weeks i might strip it back down and test all the joints and resistors
Many Thanks
Mike