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Am I really this dumb? I think I fried my board!

 
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workshed
suffering 'studio suck'


Joined: 28 Nov 2004
Posts: 499
Location: Washougal, WA

PostPosted: Tue Feb 15, 2005 6:46 am    Post subject: Am I really this dumb? I think I fried my board! Reply with quote

Tonight I thought I'd take a break from work and try to hook up my patch bay. I needed to test out a snake I just got from eBay, so I thought this would be a good excuse. I normalled the first 8 direct outs from my Soundcraft Spirit Folio SX to the MOTU 2408's 8 analog inputs. The direct outs were the only connection to the board aside from a mic cable to test out the patches.

Then I put my other pres on de-normalled channels on the patch bay, the theory being I could just bypass the Soundcraft pres and use another pre on that channel.

So as I was trying my other pres, hooked up as such:

SM58 -> External Preamp -> out to patch bay -> patched to MOTU input (theoretically breaking the normalled connection to the board)

I did a dumb thing and accidentally hit the Phantom Power switch on my Art Tube MP while it was patched in. Turned it off right away. I was under the impression that hooking into either the input or the output of the normalled pair via the patchbay would break the connection between the two so I didn't think much of it, but maybe I was sorely mistaken.

Shortly thereafter, any connection on the board sounded distorted and was accompanied by a horrible buzzing/humming sound. I unhooked everything from the board and plugged my phones straight into the board, and there was the buzzing, but REALLY LOUD. Not only that, but all everything was turned down on the board and it still outputs this sound.

So, with the understanding that I am an idiot, would someone who knows more than I do please explain:

A) What I did to my board? I didn't think I ran any risk with the way the Patchbay was set up, but maybe I need to do some more reading.

B) Is it worth getting fixed? Any ideas what got fried and how much to get something like that fixed?

C) Or is there something else wrong that I might be overlooking (aside from me being an idiot)? I tried different electrical outlets, etc.

I'm feeling really embarresed and angry at myself right now. I hate to think that I may have just destroyed this board that I bought less than a month ago and have hardly used yet. Waaaah!
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A.David.MacKinnon
mixes from purgatory


Joined: 07 May 2003
Posts: 2906
Location: Toronto

PostPosted: Tue Feb 15, 2005 10:46 am    Post subject: Re: Am I really this dumb? I think I fried my board! Reply with quote

You may just have just created a ground loop when you connected everything via the patchbay. Take it all apart and with the board unplugged from everything but the AC check for the hum. If it's still there you've done something bad to the board. If it's gone you probably just had a grounding issue. If the problem is grounding releted make sure everything is plugged into the same electrical circuit then try hooking things into the patchbay 1 by 1. Check for hum/buzz with each new connection until you find the peice of gear that is causing the problem.
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workshed
suffering 'studio suck'


Joined: 28 Nov 2004
Posts: 499
Location: Washougal, WA

PostPosted: Tue Feb 15, 2005 1:18 pm    Post subject: Re: Am I really this dumb? I think I fried my board! Reply with quote

junkshop wrote:
You may just have just created a ground loop when you connected everything via the patchbay. Take it all apart and with the board unplugged from everything but the AC check for the hum. If it's still there you've done something bad to the board. If it's gone you probably just had a grounding issue. If the problem is grounding releted make sure everything is plugged into the same electrical circuit then try hooking things into the patchbay 1 by 1. Check for hum/buzz with each new connection until you find the peice of gear that is causing the problem.


Yeah, then I think i did something bad to the board. I have nothing connected to the board at all except AC power and as soon as I plug the headphones in, I get the horrid buzzing/humming tone. I thought it was a ground loop issue too, unti I plugged the phones straight into the board -- this tone is not normal. It's like some bad sci-fi sound effect. Feck.

I know this may be hard to estimate, but does anyone have an idea as to what could/would get fried in this case? Is it like an entire circuit board? One component? Or are all bets off? I scored this used for $250, so I'm thinking it might be a lost cause to fix it.

Thanks for the reply.
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Uncle Dub
ass engineer


Joined: 09 Jan 2005
Posts: 49
Location: Springfield

PostPosted: Tue Feb 15, 2005 5:21 pm    Post subject: Re: Am I really this dumb? I think I fried my board! Reply with quote

Quote:
[Yeah, then I think i did something bad to the board. I have nothing connected to the board at all except AC power and as soon as I plug the headphones in, I get the horrid buzzing/humming tone. I thought it was a ground loop issue too, unti I plugged the phones straight into the board -- this tone is not normal. It's like some bad sci-fi sound effect. Feck.

I know this may be hard to estimate, but does anyone have an idea as to what could/would get fried in this case? Is it like an entire circuit board? One component? Or are all bets off? I scored this used for $250, so I'm thinking it might be a lost cause to fix it.

Thanks for the reply.

I'm not familiar with this particular Soundcraft, I'd suspect the Spirit's are less modular than the older / bigger models.

Do you get the noise with no channels selected, and no faders up?

How about with no channels selected and only your master up?

You have to figure out where in the system the hum is coming from. If you can isolate it to one input channel thats injecting hum when selected, thats better news, you could limp along without that channel, or investigate getting it fixed.

If however the hum is universal, as in it's there all the time no matter what, first check the board from some other mains source (take it into your bedroom, garage, whatever, just to make sure the problem isn't mains induced). If it's still there, then there's two likelihoods.

1. You blew through the input channel, maybe damaging something in the main bus, this is bad.
2. You may have just damaged the power supply which is inducing hum, this isn't so bad, but you still can't fix it yourself (you claim to know not a lot about electronics).

You could always open up, with the power disconnected, and visually inspect it for signs of damage (burnt resistors, smoked diodes, blown out electrolytics) but they may be only part of a problem.

You could also try calling Soundcraft and asking if they have a flat repair rate or somesuch. In some single board units, they will replace the whole board for a flat fee as it's cheaper than having someone investigate each individual problem. And it can often be quite reasonable.

Depending how many inputs you need Soundcraft have some reasonably priced small mixers, that got good reviews in last months tape-op.

Don't give up on it yet though, find a repair shop that will give you a (hopefully free) estimate, and take it from there.

Like I say don't know this particular unit, or it's size, but thats some idea and options for you.

Good luck, and I always welcome surplus/scrap electronics Wink
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workshed
suffering 'studio suck'


Joined: 28 Nov 2004
Posts: 499
Location: Washougal, WA

PostPosted: Tue Feb 15, 2005 5:56 pm    Post subject: Re: Am I really this dumb? I think I fried my board! Reply with quote

lousy_bassist wrote:

I'm not familiar with this particular Soundcraft, I'd suspect the Spirit's are less modular than the older / bigger models.

Do you get the noise with no channels selected, and no faders up?

How about with no channels selected and only your master up?


Yeah, with all channels off and all faders and volumes set to zero (including headphone volume!) it makes the noise when I plug on phones. It sounds like a freaking Tesla coil!


lousy_bassist wrote:

If however the hum is universal, as in it's there all the time no matter what, first check the board from some other mains source (take it into your bedroom, garage, whatever, just to make sure the problem isn't mains induced). If it's still there, then there's two likelihoods.

1. You blew through the input channel, maybe damaging something in the main bus, this is bad.
2. You may have just damaged the power supply which is inducing hum, this isn't so bad, but you still can't fix it yourself (you claim to know not a lot about electronics).


Yeah, I know enough about electronics to be really, really stupid. I'm a pretty technical person, but for some reason electronics confound me. I'm taking it to the local authorized Soundcraft repair shop this afternoon. $50 diagnostic, but it can apply towards the repair costs.

lousy_bassist wrote:

Don't give up on it yet though, find a repair shop that will give you a (hopefully free) estimate, and take it from there.

Like I say don't know this particular unit, or it's size, but thats some idea and options for you.

Good luck, and I always welcome surplus/scrap electronics Wink


Yeah, I hope they can fix it for a reasonable fee. BTW, i double checked my patchbay setup and realized there should be no way for the phantom power to hit the patchbay -- all my mics are hooked straight to the pres, then the pres outputs are hooked into the patchbay. I'm not sure what went wrong, unless my patchbay doesn't normal as I thought it should, i.e., you have to plug into the top *and* bottom rows to kill a normalled pair instead of just the bottom. If that's the case, I only had a jack running from non-mixer preamp to the bottom 2408 input... I'm thinking that somehow the output from the preamp got sent upstream to the board, but that doesn't make sense. Or somehow when I was running the mixer out -> dbx 163x -> 2408 in, something went awry.

Maybe someone else can offer suggestions as to what went wrong. I've pretty much accepted that I messed up the board, I just want to make sure I don't do it again.

Thanks to everyone for the help and info!
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workshed
suffering 'studio suck'


Joined: 28 Nov 2004
Posts: 499
Location: Washougal, WA

PostPosted: Tue Feb 15, 2005 8:08 pm    Post subject: Re: Am I really this dumb? I think I fried my board! Reply with quote

As a follow up, I started to do some more testing of my patchbay, as was suggested by someone in another related thread I started. I started to notice line noise on channel 1 and 2 of the MOTU. I thought that maybe I had also fried those two channels of the MOTU, so I bypassed the patchbay and took a pre straight in and it was fine. As it turned out, the PC Cards in slots 1 and 2 of the patchbay were bad -- either they came that way (bought it used) or whatever killed my board also fried them.

Also tested the normalling on my patchbay and it works as I thought -- it only kills the normalled path when you plug into the bottom jack of the slot. So with that, and knowing that I wasn't running Phantom power to the patchbay, I'm now stumped and worried that whatever it was might make a repeat appearance once I get my board all fixed.

Is there any chance a bad PC card in the patchbay could have caused this havoc? I'm guessing that they were fried when the board was, but want to make sure I don't overlook anything.
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workshed
suffering 'studio suck'


Joined: 28 Nov 2004
Posts: 499
Location: Washougal, WA

PostPosted: Wed Feb 16, 2005 1:47 am    Post subject: Re: Am I really this dumb? I think I fried my board! Reply with quote

I'm going to keep updating this thread for the good of the board, as a point of reference for any other pour souls who might find themselves in a similar situation someday.

I dropped my board off at Inner Sound tonight. They seem to think that most likely one or more opamps were fried. This is good news if it is indeed the case, as those are cheap and easy to replace. He said that since more than one channel is out, the board may use a summing opamp, in which case it would mean less opamps to replace.

The bummer is the $90 bench fee for mixers.

Here's what I know (some of this is restating earlier observations):

- I can't see how phantom power could have gotten to the board. I was not running any preamp inputs through the patchbay. My initial suspicion of that was my utter shock talking. Unless Phantom power mysteriously travelled through the output of my tube mp, I'm pretty sure that wasn't the culprit.

- I believe my AP patchbay defaults to HALF normalled. After testing it I found that you have to plug into the bottom row to break the link on the normalled pairs, not both rows. Yes, I should have done this test before hooking everything up. I have no idea if this is what caused the problem... perhaps I patched into something before breaking the half normalled connection and something went the wrong way back into the board.

- Because of the above items, I'm wondering if the Tube MP output somehow got sent back to the board's direct out on a channel. This is seeming like the most likely cause, based on what I tried.

- The other thing that may have been a problem could be that at one point I was trying my dbx 163x units... sending the mixer out to the compressor, and the compressor back to the MOTU in. Maybe there is something I was overlooking in that chain. Would the direct outs fry if they meet too much resistance on their way to the MOTU? Is it more advisable to run the 163x units on the channel inserts rather than in the signal path to the MOTU?

I know, I know. I ask too many questions. I'm thinking out loud here.

Will post an update when I hear back from Inner Sound.

-Bret
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