XR-1200 Quit working

[Novo]

Love the forum, wish I had more time to read. Need some help. I teach, husband, parent and then do some sound. My XR-1200 quit sending sound to the amps. My iPod sends sound out of the speakers from the power amp in jacks. I get a weak sparky signal if you turn everything up using a channel and the A/B sliders.
I haul speakers and amps, run sound and solder but that is as far as I have gotten in my knowledge base. I know the roadie's screwdriver. Didn't work. Anyone run across this. Later I can do full tear down and maybe drag it to Meridian but right now there is not a lot of time....later means maybe mid to late August.


Thank you,

Novo.

[Enzo]

Use the roadie test set - a spare guitar cord.

Plug one end into a power amp jack. We already know the power amp works. Touch the free end tip just to be sure. Get hum? Now apply some test signal to one of the input channels, and turn it up. Plug the test cord free end into either MAIN OUT jack. Get sound that way? Might as well test the SUM OUT too, turn up the sum control and plug into the SUM OUT jack. Sound? Doing that bypasses the graphic. A dead graphoc can kill the output.

I am concerned that both channels are out, did they both die at the same time?


Now the power amps are stand alone, the mixer has its own power supply circuits. All the ICs on the board use +/-15v for power, check that the ICs are all GETTING this. A dead supply can sure kill sound. ANd note that all the ICs that drive an output jack, like MAIN OUT, MON OUT, SUM OUT, run on +/-14v. Each 15v ssuply has a little transistor circuit to make 14v.

And if you have another amp around, a guitar amp or anything will do, you can send a cord from any of those outputs, MAIN< MON<EFF, over to it for a listen.


SO the fist step is to isolate the problem. It is the mixer section itself, or the graphics, or the power supply. And don;t forget, the power amp in jacks have cutout contacts that disconnect the stream from the graphic. They get dirty and no more signal. Seems unlikely both jacks would fail at once though.

[Novo]

Xr-1200 quit

Thanks Enzo! I will try this soon and get back to you. I had thought about patching parts of the mixer to my XR-600B and seeing if I could isolate the problem. Both amps work from the power amp in jacks.

Novo

Use the roadie test set - a spare guitar cord.

Plug one end into a power amp jack. We already know the power amp works. Touch the free end tip just to be sure. Get hum? Now apply some test signal to one of the input channels, and turn it up. Plug the test cord free end into either MAIN OUT jack. Get sound that way? Might as well test the SUM OUT too, turn up the sum control and plug into the SUM OUT jack. Sound? Doing that bypasses the graphic. A dead graphoc can kill the output.

I am concerned that both channels are out, did they both die at the same time?


Now the power amps are stand alone, the mixer has its own power supply circuits. All the ICs on the board use +/-15v for power, check that the ICs are all GETTING this. A dead supply can sure kill sound. ANd note that all the ICs that drive an output jack, like MAIN OUT, MON OUT, SUM OUT, run on +/-14v. Each 15v ssuply has a little transistor circuit to make 14v.

And if you have another amp around, a guitar amp or anything will do, you can send a cord from any of those outputs, MAIN< MON<EFF, over to it for a listen.


SO the fist step is to isolate the problem. It is the mixer section itself, or the graphics, or the power supply. And don;t forget, the power amp in jacks have cutout contacts that disconnect the stream from the graphic. They get dirty and no more signal. Seems unlikely both jacks would fail at once though.

[Novo]

OK, so A and B and Sum outs send nothing to the Amp in. I do get a signal from the send section of the channel but only the gain works.

More later

Novo

[Novo]

OK, So I finally got my meter out and checked the voltage to the Main mixer board = 16 Volts either side. So the power is going to the mixer section. I pulled the ribbon cable to check if the input channels are messing something up and then applied the roadie's tester to the aux in...nothing.

So now I need the schematic and lots more time

More later.

Novo