soundcraft spirit m4 mixer troubleshooting

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

You might've found the manual, but you've obviously NOT read through the whole thread (or not carefully enough).

As you can quite clearly see in the schematics, all the op-amps are NOT powered from a single supply, but from a split-supply.

Look on page 2 of the service manual, on the bottom, mid-right side. What do you see?

Yes, opamps CAN be used with a single supply, but if that's (clearly) not the case here... What's the point?


https://www.badcaps.net/forum/showpo...30&postcount=5

"The negative", in this case, is the -13.7v at pins 9-10 of CN6.

ok i am on sheet 2 and cannot see a single ne5532 or any reference to the power supply for them . this manual is one of the worst i have ever seen .. its more like a bloody car wiring diagram with numbered wires .
and where is the actual regulated supply diagram ? this is where to start as i suggested at the start of this thread .

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

You might've found the manual, but you've obviously NOT read through the whole thread (or not carefully enough).

As you can quite clearly see in the schematics, all the op-amps are NOT powered from a single supply, but from a split-supply.

Look on page 2 of the service manual, on the bottom, mid-right side. What do you see?

Yes, opamps CAN be used with a single supply, but if that's (clearly) not the case here... What's the point?

whoa, I think I should have re-read my post after replying, it is a bit unllegible, sorry about that.
I was reading volts, and i had the black lead on the chassis holding the boards.

And yes, CN6 has a 42V at pin 1, +13,7v at pins 3-4, and the negative at pins 9-10.
And CN9 has correct voltages at 3-4, 9-10.

https://www.badcaps.net/forum/showpo...30&postcount=5

"The negative", in this case, is the -13.7v at pins 9-10 of CN6.

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

like this ...

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

Pin 4 will most definitely NOT go to a ground - all the opamps in this mixer are supplied with symmetrical voltages (roughly +/-13v as measured).

petehall347, have you even looked at the schematics? They're linked in one of the posts on the first page. It's best not to assume too many things, when "blindly" (no offense) instructing less experienced people to connect and test things, imho...

I don't know what ancient datasheet you dug out that picture from, but it's... inaccurate - https://cdn.badcaps-static.com/pdfs/...cb7311d307.pdf

i got the manual from an earlier post . what page is the power supply on ?
and yes ne5532 can be wired both ways as far as i am aware .
i did say trace where pin 4 goes to too be sure .

[Khron]

Re: soundcraft spirit m4 mixer troubleshooting

Pin 4 will most definitely NOT go to a ground - all the opamps in this mixer are supplied with symmetrical voltages (roughly +/-13v as measured).

petehall347, have you even looked at the schematics? They're linked in one of the posts on the first page. It's best not to assume too many things, when "blindly" (no offense) instructing less experienced people to connect and test things, imho...

I don't know what ancient datasheet you dug out that picture from, but it's... inaccurate - https://cdn.badcaps-static.com/pdfs/...cb7311d307.pdf

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

i have just been all over the manual and they seem to have conveniently missed off the power supply .

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

always check data sheets and the manual ..
i know some op amps will work from single or dual voltages ..
you need to trace where pin 4 goes . and use that ground point as your ground point . that is of course its being fed with a single positive supply only .

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

http://vakits.com/sites/default/file...uct/NE5532.JPG

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

No, the trace seems to end after r457 and r466, they are just after the pan pot on monochannel1, and should go to switch12 at masterA.

It doesn't dissapear, but it is greatly reduced, from there I have to turn the gain right up untill it clips to hear a faint something.

The opamps are ne5532, and checking the otrher opamps of masterA, it seems like the whole line is out, they all have the same 0.7v on one of the Vcc ends.... gonna check master B

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

what op amps are you checking ?

[Khron]

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?

[5inc]

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....

[5inc]

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.

[5inc]

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?

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

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

[5inc]

Re: soundcraft spirit m4 mixer troubleshooting

Does that mean it doesn't matter the side?

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

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

[5inc]

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!

[petehall347]

Re: soundcraft spirit m4 mixer troubleshooting

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

[5inc]

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?