drswift Posted August 12, 2007 Share Posted August 12, 2007 hiive had this 24 channel soundcraft spirit live sitting around for a couple of years not being used. ive plugged it in recently to test it out and there are a few problems. The main one is that the right channel seems to be a bit temporamental. With enough level driven through it, it will be happy to wake up and work fine for a little while, but otherwise it only passes through very weak and distorted signal. ive pulled the circuit board out, all capacitors seem to be fine (none swollen or leaky, and any that were showing continuity on the circuit board showed no continuity off the board), ive gone to town on the electrical spray and shoving leads in and out of insert points etc. the fault isnt due to a channel. Also, the signal is failing before the level indicator LED's, so its not the outputs (ill also mention that these LED's are working when I PFL a channel so this isnt the cause either).Any ideas? im not really trained in any way to fix this sort of gear but I seem to find my way along pretty well most of the time. do I need to follow some sort of trail along the circuit board with my multimeter (comparing it to the left side of the desk)? would love to hear any suggestions anyone may have. Link to comment Share on other sites More sharing options...
Shez Posted August 12, 2007 Share Posted August 12, 2007 do I need to follow some sort of trail along the circuit board with my multimeter (comparing it to the left side of the desk)? That's not a bad approach. Assuming you can get sufficient access to the board in situ, then tracing backwards along the signal path whilst feeding tone through both channels should help you spot at what point the signal starts to be present again. If you can get hold of (and follow) a circuit diagram, that would make it easier to see what's going on where. Link to comment Share on other sites More sharing options...
drswift Posted August 12, 2007 Author Share Posted August 12, 2007 cheers I'll try that. so I guess by your advice you are suggesting that its best to work from the outputs backwards, rather than trying to find where the signal enters the master section and travelling forward from there...? I suppose going backward does make sense as it might be a bit tricky knowing which of the 14 pins carrying signal into the master channel are the ones carrying the left and right mix. Link to comment Share on other sites More sharing options...
Rob_Beech Posted August 12, 2007 Share Posted August 12, 2007 You are right to go backwards. This should show you where the problem is hopefully. Does it do it from individual channels, or channels from the groups, or both? Not sure which model desk it is so can't really say much more. Link to comment Share on other sites More sharing options...
drswift Posted August 12, 2007 Author Share Posted August 12, 2007 the desk doesnt have any groups, and the right channel thing happens no matter which channel im using. I think one or two channels do have their own similar problems (of needing a large boost of signal to wake it up) but I can look into that one another day.cheers again for your help hey just to make sure, do I just need to run the desk pretty hot (without sending the outputs anywhere), and use the multimeter to measure voltage down the line? Link to comment Share on other sites More sharing options...
Shez Posted August 12, 2007 Share Posted August 12, 2007 do I just need to run the desk pretty hot (without sending the outputs anywhere), and use the multimeter to measure voltage down the line? If you feed 1k tone through it at somewhere between 0 and +6dBu, you should get *roughly* 1vac reading on your meter. An analogue meter is sometimes more useful for this kind of thing as the exact reading doesn't really matter - it's the presence of a signal you're looking for which is easier to see from a big needle swinging about than digits flickering around. Link to comment Share on other sites More sharing options...
Mixermend Posted August 12, 2007 Share Posted August 12, 2007 When faced with a problem of this sort - try and exercise the insert jack sockets - by inserting and withdrawing a plug a few times. This is quite likely to be the cause of your fault. The switch contacts through which the signal passes when the socket is not in use for a while occasionally oxidise or develop a high resistance film. As you have similar symptoms on channels also - this is almost certainly the case. A useful addition to your tool box is a TRS jack plug with a soldered link between the tip and the ring - insert this and see if that solves the loss of signal. Do you see the unbalance, or change in level, on the bargraph metering? John Link to comment Share on other sites More sharing options...
lightsource Posted August 13, 2007 Share Posted August 13, 2007 Try to get your hands on an Oscilloscope, seeing the problem is a lot better than just reading numbers of a digital multimeter. As Mixermend says, it's probably a bad socket, or possibly a dry joint on one of the PCB's Link to comment Share on other sites More sharing options...
Rob_Beech Posted August 13, 2007 Share Posted August 13, 2007 John, the OP has tried the insert trick and has mentioned that the signal fails before the output meters. This really sounds like a board issue somewhere, I'd think it could just be dirt somewhere, a good clean may cure this, I've had boards do this from time to time and have a couple of power amps that do it every so often. One big bang so to speak and they're working fine. Get the desk cleaned up. have a look for bad solder joints whilst you're there and see if it improves. I've got an old Live 4 somewhere* which if kept cleaned up is spot on, they're great desks. * Somewhere......... for 2 months I've been looking for it, I really have no idea where it is. I've looked everywhere. Has anyone seen it? Link to comment Share on other sites More sharing options...
fitz_e Posted August 13, 2007 Share Posted August 13, 2007 Sounds like a dry joint - I've tested some old analogue Dolby boards before, and they would either output nothing or a really low/distorted level; injecting a big signal (so generating some heat through a few components and closing any o/c there may have been in the signal path) or even repeatedly powering on/off would get them going (as would methodically tapping the board with the handle of a screwdriver). Occasionally it would be a resistor going intermittently o/c, but in the main it would be a dry joint (board or connector). The "nice" bit of this problem is that you've got a working left channel, which gives you something to compare the RHS to. Re-seating any inter-connectors can be an easy remedy. Link to comment Share on other sites More sharing options...
drswift Posted August 14, 2007 Author Share Posted August 14, 2007 hi and thanks heaps to everyone for taking the time to respond to my post.so anyway here is an update on what little time I have found to focus on the problem..... just to rule out the insert thing, I ran sound through the desk while joining the tip and ring section of the Right master insert. no luck there. I also forgot to mention before that I have already been over around 3 quarters of the solder joints on the right output circuit board with my soldering iron. maybe I should take it out and finish that job. also, today I followed signal back a few steps from the outputs backward but then ran out of time...and started to realise how tricky that approach is going to be. A friend of mine suggested it could be a transistor on the board. considering how tricky following the tracks on the circuit board is going to be, is checking out transitors a feasable option? if so, how do I check transitsors? thank you so much again! Link to comment Share on other sites More sharing options...
Shez Posted August 14, 2007 Share Posted August 14, 2007 I don't think a duff transistor will cause the intermittent problems you seem to be experiencing. An iffy solder joint / connection between boards is much more likely. If you can get hold of a schematic / service manual, it would make life somewhat easier as tracing signals blindly on a board isn't the easiest of tasks. Link to comment Share on other sites More sharing options...
JPSTechie Posted August 14, 2007 Share Posted August 14, 2007 If this is the correct desk then a block diagram can be found on the last page Here Link to comment Share on other sites More sharing options...
drswift Posted August 14, 2007 Author Share Posted August 14, 2007 yeah thats the desk. so is that all I need to be able to trace the signal?I'll give it another shot tomorrow and see what happens.cheers Link to comment Share on other sites More sharing options...
drswift Posted August 15, 2007 Author Share Posted August 15, 2007 hi again, I followed the circuit board from both ends (signal entering and signal leaving the RHS). my head became a maze of confusion before too long. im going to try the remaining solder joints tomorrow - if that dont cure it I may accept defeat and pass it onto someone qualified. cheers again. any more ideas if re-heating the solder joints doesnt work? could the problem be coming from another part of the desk? Link to comment Share on other sites More sharing options...
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