soundcraft spirit m4 mixer troubleshooting

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

ah .i have got a feel for the way they left clues ... r667 is limiter for positive supply so r666 should be replaced with same value ..
i hope r667 is there or i will be cross with who has been playing around with it .

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

sorry, only those two mentioned earlier(it's all so big and crazy my mind is playing tricks on me), trying to write it down but i'm too tired to make it readable.

Gonna search through my scavange box and if I find one I'll stick that in. It doesn't matter what size it is as long as it is not smaller right? wattwise

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

Yeah, "even" the stock ones will be maaaaybe 1/4watt ones. There's not a lot of current being drawn through them (maybe about 40mA at idle), so they won't need to dissipate much power (~16mW at idle).

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

10 ohms .. try 1/4 watts if you have one .
say if you put a 2 watts in you risk burning out traces and more ..think of it as a fuse .
r667 size should give you a clue to wattage .

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

I don't know about smd mount resistor values... it's pretty small, like... 3mm from side to side. I found what I think is a 1/2w 10 ohm resistor, will that do?

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

Sounds like more than enough At least for testing, it should do fine.

https://en.wikipedia.org/wiki/Surfac...minal_packages

I'd be surprised if it was any bigger than a 1206 (3216 metric).

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

ok, the one I found seems like it's a 1/4, the size is about 6,5mm long

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

Yep, plenty

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

i personally wouldn't use a 1/2 watt in that position . especially for testing purposes
try with power off and checking resistance from pin 4 of the ne5532 to ground . if it shows low ohms there is a short somewhere .
would also be a good idea to check voltage on negative side of c386 . to be sure its not too high .

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

I installed it and it still seems quite the same.

I tried resistance from gnd to pin4 and it gave me 1.74kO. Then I switched it on and tested between c386 for voltage and I get -12vdc.

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

is that at the negative side of c386 reference ground ?

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

sorry, I don't quite understand the question as "reference ground" is new to me...
But I can't see any direct link to gnd from there, if that is what you mean

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

He might've been asking whether you measured that voltage with the black probe on a ground point, but since one end of that capacitor is connected to ground... i'm pretty sure you did

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

one end of c386 goes to ground?? I see it goes through c370/c242/c298 on the positive side to AGND; and through c371/244/299 on the negative, to AGND again.

does that count as being connected to ground?

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

Hmm, i might've mis-read something. What page can those caps be found, in the schematics?

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

c386 is in page 15 middle right end, the others are page 10 middle bottom

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

negative side of c836 goes to r666
positive side to r667 .
you could measure the voltages at those resistors .
if one side of r666 is low voltage measure voltage right across it .then work out the current draw using ohms law

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

ok.. voltage drop is 0.4V, resistance is 10 ohm and power is 0.25w, and ohms law says I=P/V or V/R, so that would be 0.25/.04=0.625A or 0.4/10=0.04A.
What am I doing wrong?

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

there is a 40ma current draw according to voltage drop .
or 0.016 watts 16mw
what voltage is at the resistor ? it should be same for both resistors except r666 negative .r667 positive .

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

whooooa, I have master outputs working!! somewhere along the way they started working, I found that tracking towards aux outs, seeing the mute switch(sw10) under return master pot(VR13) was on, pushed it out and AUXouts, MONO SUM, MIX L/R started working!
Now I still have Monitor out and phones out that aren't working just fine. Monitor sounds distorted with a loud hum, while phones still sounds like it's frying the phones, from the second you plug it in even with volume all the way down...