Mixing Desk Repair - Soundcraft EFX12

[Music] and today on the bench I've got a mixing desk this is a rather modern 12 channel job it's the Soundcraft efx12 and there's no output and I consider this to be a rather fancy mixing desk for the features loads are knobs sockets and Sliders if only when you're what they all did I won't wash some of them at wonky hmm and it features some lexicon technology a 24-bit digital effects processor I hope that's not knackered well this could take quite a while to check out and there's a lot going on but the power sockets on the bottom and I'll start with channels one and two and I'll monitor the monitor outputs although it says monitor output there hmm let's get some power on it oh there is some life but nothing coming out of it let's try these uh sliders not even twiddling this helps see I'm never sure if this is the fault or I just don't know how to use it let's try some other outputs ah we got something wow and that's been affected by the sliders for the left and right mix that's good I should be able to see the two signals I'm injecting so there's channel two there's a sine wave I think two kilohertz and there there's a one kilohertz triangle wave when you mix the two together and you get that my attention is drawn to this someone's added this label on here what's going on there oh no that's not good there's about what one volt offset there what about this one same there that's not good so this thing's definitely got to come apart and that's going to be quite a lot of work so I want to check that I've captured all the faults on this before I do that let's put it in the only working output we've got and just I need to set all these at similar settings what I want to do is check that all the inputs are working because when I take this apart and I know that I'm dealing with all of the faults together helps if you turn all the sliders up as well so now you'll see the same output on every channel so yes yeah it's gonna be good so far I'm going to do the same with the microphone input so I need to change my cable this is another balance signal and it's not the amplitude down in there say 30 millivolts testing the same way just go from socket to socket and last but not least that one good until I've not seen any life out of this what's going on there might help you press this prefabe to listen and it does and it responds to the gain as well that's something working that I didn't think was and of course now there's something to monitor the headphones were monitors working left and right and they're still giving DC out and I still don't know about this I'm not sure what it's doing it seems to do something quite what I don't know well I've seen enough let's get it apart [Music] mixing desk type ages to get inside they weren't always this bad the other mixers have separate modules for each channel so you didn't need to take all the knobs off and you could just remove the channel that had default that was probably until the 90s now they make them all like this because it's cheaper less Parts unfortunately you have to go through all this palava just for the simplistic servicing JK now look they've used every time you're faster on this it's a bit of a workout yes there's a lot of parts a lot there's 17 fader caps 118 knobs 39 Jack socket knots 39 washers to go with it 47 screws that's the total of 260 Parts just to get the lid off foreign [Music] little plastic washers to get off you know what these things can wait to the end I'll just tip them out or something you can hardly see them Frankie and in they go we're not done yet there's more screws [Music] foreign [Music] well the board's very neat look at this laid out with some OCD I reckon every uniform got a bit of logic going on here it's probably to drive this bar graph and this must be to the sound processor there's no way any of these chips do same processing in some respects this is better because you've got so many duplicated circuits you can spot problems a bit more easily there's nothing to say wrong about the naked eye it looks very tidy let's show it lights up with a close off I'll tell you what though a bit of a whiff coming off here it's a bit hot well just surveying the board oh straight away look at these these chips here oh there's one how hot's that 57 degrees crikey oh and there's more here oh these must be the ankle chips 60 degrees yeah I knew smelled a bit warm oh there's another two hot ones here ah these are the same op-amps as the others yeah not sure and this slot are all running cool there and they're all the same temperature nice now these all look okay nice steady temperature just looking at the side there's a board underneath and that looks pretty warm um 55 degrees or so yeah turn that off I think I need to take this board out and have a look underneath hope that's not a big job and of course that means more screws [Music] [Music] I imagine this is the Lexicon effects board a little plastic screws on here we'll just get those out the way okay there's the brains this is definitely the digital signal processor or the effects board you can see a big fat DSP TP Harman audio DNA that's got to be it probably some memory there and God knows what clever stuff but is it getting hot I'll put an insulator behind there because otherwise it will get hot we'll Power It Up let's get the camera on it oh it's a bit of heat building there about the rest of it core of the chip I don't think that's a problem measure from the ground there to there yeah we've got five volts about the input yeah nearly eight yeah nothing wrong there so this can go back then I don't know where confusion so I think it's quite a lot of damaged chips on here they're all there op amp chips and uh I think someone's done something naughty to this let's take the board off just pop this ribbon cable out if I can it's a tight one and the power supply connector lurking in the dark and hopefully this will come off yes so we've got a total of six chips to change and the good news is they're all the same they're all njm5532s and the three down there they're probably these three is getting them they are buried around these sockets and these are quite tall and I'm going to be using hot air to remove them and replace them and I'm also concerned these are going to melted so these sockets need to come off although this one's accessible it's pretty close to this plastic switch and I don't know ruined that and these two aren't near anything plastic so and these are okay these are actually quite easy to change foreign still tight [Applause] I'm just going to flood fill this one otherwise I'll have to change the tip on the desolding tool and I don't think it's worth it [Applause] well that's cleared the way for these now I can actually get on and unsold with them flicking them up it works I suppose foreign a lot easier and I'm also going to add a little bit of extra solder mainly because it's got a lower melting temperature I'm just going to put the chip on nudge it into position and there's one just going into a rough position [Applause] I just moved the board around so I could get in it a bit easier I'm just going to rework this one foreign melted it a bit one effects its um performance but try not to do too much of that I'm just going to clean the flux off this board so it just looks a bit tired here because it is quite sticky stuff all right I don't think it hurts anything not significantly well that's a bit of practice for the next three I've got my eye in now we're going for IC number four so the first one I saw glowing away again just get some heat in it's only if they're connected to ground that you have the big trouble see if that's willing to move you [Music] put some fresh solder on might clean it up a bit as well first foreign because I've got no patience on with a bit of flux to the hot air touch these legs up just in case doesn't hurt so they pass the nudge test and there's these two chips left now that were also glowing to be honest I could have checked the signals coming in and out but to be fair this Chip's quite cheap and if I've got to change one I might as well just get on with the lot grabbing it in anticipation of it coming loose they're off now do this spawners right away because that took a lot of time to get the heat into the board and uh I'm hoping it's traveled oh I'm not liking that the bottom of the sliders melting oh I'm abandoning this I'm not liking what it's doing to this slider here that could be a problem it shouldn't be bubbling outside like that hopefully it's just minor damage until this the old-fashioned way just give it a bit of a drowning in solver foreign leg on check the alignments yeah it looks okay just tuck that leg okay and just get the iron just to go and warm all the legs up one at a time like that let's give it a little nudge check nothing loose outside yeah they're okay just wash that sticky flux residue off that feels okay fortunately yeah I think it's only cosmetic not too wood well I think that's the sort of damage you do when you put phantom power on the output of your mixing disc hopefully I've got it all I'm gonna put the sockets on though to test it put this switch back in as well won't work properly without this I'm sure of that it's a snug fit though [Music] and these sockets as well these are also fairly tight in there so I suppose it's a good thing make sure getting the right way around got that sort of corner on them [Laughter] thank you let's get this ribbon cable back in and it's a bit tight there might need a bit of a push for the screwdriver okay power cable it's bit of a awkward once again put it roughly in place I'm going to draw the auxiliary and the effects I put well we got something so the effects are working for change options different things are happening okay if they work we'll do the next ones this is the stereo output number one no nothing there try channel two still nothing oh that's working that's the headphones and they monitor they're working okay I just noticed the waveform's not right I've lost a channel it's checking all the buttons at the right level yeah we're not not muted what's Channel One Channel one's not working but it weren't before so I think it's a broken connection or something I might just seeing if I can just poke around and provoke something to happen oh hang on is it this part here this is the balance or the Pan pot look at that Wiggles on and off like a switch it's not this capacitor is it now there's something it doesn't even like that mute it sort of affected a bit something around here there's not a lot underneath this board as we saw there's no components where I'm pinching the board I'm just coming back on and off it could be a bad fire but I don't know I've done before very quite rare something this clean as well oh do you know what is this resistor I think it's resistors dodgy or at least the soldering of it is dodgy oh oh oh oh dear well I never it's broke in half the end caps come clean off that's supposed to be 10K resistor these resistors come on at a rather large rail so it's a bit annoying sort of Peel one off start this thing open come on where'd that go show me it's a good job they come on Rails of five thousand anyway there it is clean it a bit put it roughly in position and just touch it with the iron just get the iron to wet both pads at the same time that'll do well that was an annoying foot wasn't it so is Channel One Alive now oh yes I think that's good actually yes so I've got one sine wave and another one yes yes definitely turn channel two off yeah both off yeah okay that's that fixed if I rattle the pots nothing goes wrong good I'll check there's no more like that so just work one channel at the time check it's working so that one's on yes I've did this before that's working and that's working that one's working this one and that one oh that's not working what's that channel 12. don't suppose not another crap resistor have we the chances are that eh well this is another channel that worked before so I'm thinking it's mechanical damage again I don't think it's an electronic fault it's just gone the old finger probes off again just to point out this is all that voltage stuff the power supply is well out of the way oh what have I done let's come back on what did I just do oh look oh same bloody wise got broken wire because it reaches I'm just going to put a blob of solder on there on The Wire and just tap that back on how's she looking there's one here that's been cut in half and another one broken here I don't think I'm the first person to open this thing up that's perfect that's working great no missing has it fixed the other channels so this is Stereo channel one no nothing there and channel two still no good well to fix this last problem I need to use another oscilloscope I think stocking how it's laid out in the stereo Channel there's a ground wire because it's got no signal on then there should be a left and a right neither have got signals on same here and these wires aren't broken I've checked and we've got op amps down near the fade as for the stereo channel so you've got pin one should have been output and of course there's nothing but it's the inputs I'm interested in nothing on any of those pins up here no no no just noise really same for both channels which I'm finding really strange but I do spy these resistors and think of his same broken resistors already yes big loud signal there and there well different volumes made you but nothing on that side and nothing on that side I think we may have a problem there of course we can measure the resistance of them in circuits see what they'd measure 3.4 okay in that one about this one 3.1 I can't actually see what they're supposed to be damn getting old they're both 10 kilo ohms so you know it's not bad but I want to check the um output so from ground measure resistance to there and we got 940 ohms okay here oh God dead short hmm I just had another look at the lid of this mixing desk and I've noticed that these stereo outputs are actually inputs that's why there's no signal there's even a gain knob for each one that's definitely input terminology it even shows on the block diagram look so if I put these in the monitor outputs and try an input well look at that and the other stereo Channel yeah perfect and the fighters work too nothing wrong with it well that ends up for lava now there's only a couple things left to check I can remove the monitor output now let's check the main mix rifle it does require a change of cable because this is for a balanced diet course so I'm going to need to put these in because my cable's got crocodile Clips on the end just pull the ground on there put the one half of the balance signal there one over there come on very balanced output there's a waveform missing hmm it might be just cheaply implemented mind you but at least that's working let's check the other socket that's also good this is stunts on the cheek look goes to the hot connection and the call connection is just resistor to ground the last socket's just to check the other stereo ones the last thing to check is the phantom power for the microphone and it should be 48 volts on here well we're on the home straight now and adjust the obligatory Port twiddling test uh there's a lot of Pops this kindly quite monotonous foreign start twiddling looking for trouble no problems there well that's everything tested on here that I know about so that's it it's time to put the lid back on [Applause] [Music] and these plastic washers on what I use since these are you can hardly see them well here we go you know my thoughts and all these knobs far too many and I think they're worse to put back together than they are to take apart although they're not so tight [Music] foreign thank you well they're great fun to play with but I hope I don't get any more of these in catch you next time

Channel: Mend It Mark

Views: 102,920

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Id: ouoAIWlAAK4

Length: 33min 47sec (2027 seconds)

Published: Fri Feb 10 2023