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soundcraft spirit m4 mixer troubleshooting

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    #41
    Re: soundcraft spirit m4 mixer troubleshooting

    see if you can find the stain where the water got in ..it might be a clue

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      #42
      Re: soundcraft spirit m4 mixer troubleshooting

      hi there I'm back,
      It's too late to look for a stain, I've had it for so long sitting on the shelf, when I picked it up again I gave it a little brush. That was before knowing it got wet. But it was a good idea, thanks, I'm taking a note for the future.

      Now, I had the signal tracer that was linked at the beginning, but I had to make a new one with a little potentiometer because the only battery amp I have right now is one of those eggy mp3 speakers, with no volume control and only one miniUSB input. Done.

      So now i'm starting to test it, and for a first check I tried eq's and gain pots. And it sounds! ^^

      Following the scheme I managed to find a couple of bad resistors for now, but I don't think that's the major trouble... I'll grab a cup of strong tea and get on it.

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        #43
        Re: soundcraft spirit m4 mixer troubleshooting

        well done keep searching ..

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          #44
          Re: soundcraft spirit m4 mixer troubleshooting

          hey, I took those resistors, but out of circuit they seem ok.. they are r592, r593 and their couples at the "P/B replaces mix"(master A page)

          I also got a weird resistance reading at the resistors after the pan pots at mono at mono channels (i'm sticking to those for now), but just like the ones before mentioned, I believe the circuit is fooling me, since they all have the same readings...

          Signal vanishes around the Opamps, they have power, but not much sound after r457(mono input cannel 1).. dunno if it is because of it's value or what.. tomorrow I'l tackle it again.

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            #45
            Re: soundcraft spirit m4 mixer troubleshooting

            Sounds like progress

            I recall 3-4 years ago, buying a Soundcraft FX16-II that had gotten something spilled on it (i might be wrong, but i do recall i bought it as faulty). Actually yeah it did, i'm starting to remember having to "patch up" some power traces going to opamps, that had been corroded by whatever it had "drank". I might've had to replace an opamp or two as well, but it's been a long time
            Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

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              #46
              Re: soundcraft spirit m4 mixer troubleshooting

              yes, it is. I am blissfull.
              It's like a new dimension opening before my eyes! Now I got to a point where the signal goes bad, and further on I just can't keep tracking.

              Is it the time to build a cable for signal injection? Is it as simple as picking up a jack and shoving a blocking cap and some resistors in between like the tracer?

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                #47
                Re: soundcraft spirit m4 mixer troubleshooting

                For signal injection, (in)to where? Right after the point the signal gets lost, or..?
                Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

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                  #48
                  Re: soundcraft spirit m4 mixer troubleshooting

                  just a blocking cap should do it .
                  you really need to have control over the level . something with a vol control .

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                    #49
                    Re: soundcraft spirit m4 mixer troubleshooting

                    Yes khron,
                    to inject just past the bad point, so I can look for further trouble while I wait for the pieces to arrive... do you think that's a bad idea?

                    I allready put a little pot at the tracer, i'l just do the same on the injecter...

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                      #50
                      Re: soundcraft spirit m4 mixer troubleshooting

                      btw, the cap goes in series through right/left or through the negative lead?
                      or doesn't it mind?

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                        #51
                        Re: soundcraft spirit m4 mixer troubleshooting

                        cap on probe . negative/ground to chassis or ground point if floating ground

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                          #52
                          Re: soundcraft spirit m4 mixer troubleshooting

                          Sssugar, i just did it the wrong way around.
                          I got a cut minijack lead that was chopped off, and connected the negative ground of it to the cap and the pot, and that was going to be neg/gnd, then the other 2 wires were going to be the probe.

                          If I wanted to have 2 probes, should I have a cap on each? would it be possible just like that, to test both L&R at the same time? I'll stick to one for now, just asking

                          thanks!

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                            #53
                            Re: soundcraft spirit m4 mixer troubleshooting

                            the idea of the cap is to block dc current going one way or the other .

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                              #54
                              Re: soundcraft spirit m4 mixer troubleshooting

                              Does that mean it doesn't matter the side?

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                                #55
                                Re: soundcraft spirit m4 mixer troubleshooting

                                just put a cap on the signal side . ground to ground .

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                                  #56
                                  Re: soundcraft spirit m4 mixer troubleshooting

                                  Ok done, but it ain't doin much... i'm using the tracker to test it out, but it barely sounds, tried sliding the pots up&down and it's still pretty low, shall i try with an other cap? the one I put in is a 1uf.. maybe too much?

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                                    #57
                                    Re: soundcraft spirit m4 mixer troubleshooting

                                    wait, showing it to a flatmate it seems to work now, I don't know what happened, maybe it was a bad contact, I'm starting to have too many wires on my desk.

                                    that said, next is plugging it in to see.

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                                      #58
                                      Re: soundcraft spirit m4 mixer troubleshooting

                                      well well,

                                      Reading johnnydiaz's "How to check an OP AMP in circuit" thread, he checked for voltage at pin 8 he got 15.60vdc & pin 4 -15.35vdc
                                      I instead have 10.4vdc on 8, and 0.7vdc on 4....

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                                        #59
                                        Re: soundcraft spirit m4 mixer troubleshooting

                                        Is that the case on the opamp where the signal "ends"? And do you get the same measurement on the other opamps nearby?
                                        Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

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                                          #60
                                          Re: soundcraft spirit m4 mixer troubleshooting

                                          what op amps are you checking ?
                                          Last edited by petehall347; 01-10-2017, 04:47 PM.

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