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Old 9th May 2013, 01:47 PM   #1
Anton65 is offline Anton65  Ireland
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Default Soundcraft gb aux help!

Hi there, I just found this site its my first time posting here and any help would be greatly appreciated! We have a soundcraft gb2 that we got 2nd hand and have been using it for a while not successfully until now. Basically we are running monitors from aux1 and 2 from a stage box. For some reason aux 1 has just started making a horrible noise like crackling and popping but not a hum. I plugged straight from desk and checked and sure enough it seems to be from the desk. But then we just moved to a different aux and it was working fine but now after a couple of weeks the second aux is now making the noise! Now im running that monitor from the matrix. Sorry for the longwinded msg but my head is melted as to why this would happen. Could it be a power issue? We are also using a female to jack cable from stage box to monitor which isnt balanced. Thanks. Anton
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Old 9th May 2013, 02:27 PM   #2
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Dry joint on the pcb where the output jack/s is soldered on. Fixed several of these with that problem. Open it up and blanket resolder them all.
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Old 9th May 2013, 02:39 PM   #3
Anton65 is offline Anton65  Ireland
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Thanks for your reply! when you say blanket solder? do you mean to re add some solder around joints of xlr outputs. Why do you think the second aux would go so soon after the first one? Thanks
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Old 9th May 2013, 03:13 PM   #4
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All right. I don't know the gb2 (but have done a lot of Soundcraft consoles).

From the pictures I'd say that aux 1 & 3 are on one PC board (although with soundcraft it could well be that the entire output block was a single unit, with all the subgroup mix amps, all the aux mix amps and all the balanced drive amps {ooh, naughty. Not properly balanced at all} on one board). From the symptoms, the problem is probably here, and opening the mixer essential.

The timing suggests that a plug is falling out, little by little. Probably a ribbon connector, with all the aux mix busses going through it. I'm assuming now that you've checked that the problems the same from several different inputs. It might be worth physically thumping the outside of the box with an amp on the aux that's giving the problem and a low-level signal running through (incidentally, I assume you moved onto aux 3 from 1, and that 2 never gave the problem. Did you try 4) to see if there's mechanical correlation.

How did you test the desk outputs – with a monitor? It would be very embarrassing to strip down the console to discover the problem had been badly analysed and was in the monitor amp, or a short in the snake (unlikely from your description but worth checking, doing multiple swaps until absolutely certain). It's just possible one of your monitor amps (or active monitors) has a transient problem that's frying output chips, but unlikely.

Matrix outs? The User guide I've found has four subgroups and a stereo main; nothing I'd classify as a matrix…



From the timing
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Old 9th May 2013, 03:29 PM   #5
Anton65 is offline Anton65  Ireland
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Hey man thanks for reply, yes the desk has 2 matrix outputs also! But basically Aux 1 went and now 2 has gone. 3,4,5 and 6 work. Yes that makes sense what you are saying but I do wonder if the monitor is causing the problem because I don't see how both auxes could have gone so quickly. I tried diagnosing auxes by going through them with a monitor from desk and aux1 definetly isn't working. Aux2 worked but then during practice it went. How could i tell if monitor is causing this? Before i open up desk? Thanks by the way
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Old 9th May 2013, 05:41 PM   #6
JMFahey is offline JMFahey  Argentina
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Quote:
How could i tell if monitor is causing this?
Drive the monitor from different outputs, if it works with all except Aux1/2 then you know it's not a Monitor problem.

Same with the snake, go through it testing line by line, obviously coming from an already proven good output.
If in doubt, use another spare cable.

If you confirm problem is definitely related to outputs Aux 1/2 first recheck using another proven good spare cable just to make sure.

In a nutshell, you are using the elements themselves for self testing, before opening the case.

Crackling and popping usually points to a "mechanical" problem, meaning connectors/wiring (internal or external)/sockets/wire ribbons/cracked solder (a.k.a.cold/dry solder).

Pinkmouse suggests having a real close look at the offending connectors, under good light and I suggest you use strong reading glasses, not because you *need* them but to see from real close.
Get a good clean 30W soldering iron (wipe its tip now and then with a damp cloth to keep it bright and shiny) and one by one, redo all solder connections you see around those output connectors, meaning you apply the iron tip, wait 2-3 seconds for solder to melt (if it takes 5-6 seconds or more your iron is too small/cold) and add a tiny bit of fresh solder, so you now have a bright shiny connection, not a dull irregular one.
Don't overdo it and avoid creating solder bridges, unwanted connections to neighbouring pads.
That's why I suggest good light and reading glasses.

Chrispenycate also distrusts ribbon connectors close by, pull and reseat them, sometimes touring partially unseats them.

Carefully move the wires on both ends, you may also redo connector solder pads.

Also: do you need to rock/push some switch to use/assign/enable those failing outputs?
A dirty/worn switch may cause those symptoms too.

OK, I don't want to confuse you with 1000 options, now you have your hands full for a couple days.
Do the testing and post results.
Click the image to open in full size.
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Old 9th May 2013, 05:44 PM   #7
Anton65 is offline Anton65  Ireland
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Cheers, will do.
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Old 9th May 2013, 05:51 PM   #8
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First suspect should be any insert point TRS jacks for effects loops, if they're a single TRS jack on that baord. They're supposed to self-connect when nothing is plugged in, but the swithch contacts inside (not the plug contacts) get dirty when the contacts are open if something IS plugged in. Solder up a TRS plug to connect the tip and rig, and plug it in...if the noise goes away you know the problem was the loop insert jack, and you can either leave the plug in or clean the jack contacts.
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Old 9th May 2013, 09:08 PM   #9
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Test schedule is dependent on available gear. I generally have a nasty little analogue multimeter in my shoulder bag at all times, a miniature digital multimeter whenever the battery's not flat (it enjoys turning itself on without me asking it) a nasty little transistor amp thing with about a 11/2" speaker, and an XLR to minijack with balancing transformer in it, and a Swiss army penknife. 'Course, if I know I'm going out to mend things I've got a signal generator, soldering iron, a scope, a film can of often required components, spare fuses, an audio test CD… but it's surprising how much you can do with the basics.

Plug a powered speaker into a working output (say aux 3). Plug a signal source (preferably hands free, an mp3 player or CD; a microphone confuses matters. However, it does work.) into an input of the mixer, then turn up relevant volumes until you have a comfortable, not too loud, signal out of the speaker. Take a rubber hammer - not got a rubber hammer? - take an ordinary hammer and a piece of scrap wood, rest the wood against the side cheek and give it a firm tap with the hammer. This is not a racial slur, we're looking for bad contacts, dry joints, even cracked PC boards (although if we find those the time has possibly come to put the machine in the hands of an experienced service technician, even if it costs some.), the sort of mechanical damage touring consoles often develop. If there are no clicks, clunks or pops at this point we repeat the operation on one of the defective outputs. This will quite likely give a reaction, but unfortunately this is true whether it's dry joints on the output XLRs, badly seated connectors or just about any cracks or internal shorts. In fact, seeing that the thing has once worked, we'd be more surprised if this didn't give some reaction.

Looking at a picture I can't see how to open the thing; it seems to be a continuous face plate. Which is bad, because the next step is to open it up and give it a meticulous visual inspection. It's unlikely from the symptoms that it's a power supply problem (but that doesn't mean impossible) look for discoloured components, bulgy capacitors, badly seated connectors, solder joints with a mat finish rather than shiny (oh, and the 'blanket solder' comment was heat up all solder joints to connectors, even if they look OK; XLRs have a higher thermal capacity than resistors or ICs, and are more likely to make a poor joint with flow soldering). At least at a first stage do this with the power connector out; later you'll probably find me propping it open and going round the interior with probes, wiggling things, but I've been doing this for ages. Close it, plug it back in, and see if the problem's changed (either way).

Cyclecamper :- If the manual I've downloaded is right, no inserts on the auxes, only on the subgroups.

JM Fahey:- I do indeed distrust Soundcraft ribbon connectors; in older consoles (when they were a bit more modular than this one ) I've gone in and found bus connectors completely dropped out of sockets. I suspect employees of not having inserted them any too well originally, as they seemed pretty firm when well pressed home. However, I've never had pops; just silence when there was supposed to be signal. However, I will certify that one end can drop ou, making it not immediately obvious, and losing some functions but not others.

Last edited by chrispenycate; 9th May 2013 at 09:20 PM. Reason: checked later comments
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Old 9th May 2013, 09:10 PM   #10
Anton65 is offline Anton65  Ireland
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Quote:
Originally Posted by cyclecamper View Post
First suspect should be any insert point TRS jacks for effects loops, if they're a single TRS jack on that baord. They're supposed to self-connect when nothing is plugged in, but the swithch contacts inside (not the plug contacts) get dirty when the contacts are open if something IS plugged in. Solder up a TRS plug to connect the tip and rig, and plug it in...if the noise goes away you know the problem was the loop insert jack, and you can either leave the plug in or clean the jack contacts.
Hi, They're actually xlr outputs on desk. We are then taking xlr output from stage box. Which we are using a female xlr from stage box to mono jack to powered monitor. Should the xlr to jack be balanced or does that matter?
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