The new Raspberry Pi B Model B+ is here - Pick one up in the store and check our detailed guide!

X0XB0X very low volume.

by djones on Sun Feb 03, 2013 12:50 pm

I bought this defective X0XB0X on the web with the intent of fixing the unit.
So the issue it that the output volume is very very low.
Where do I go from here, what could be the problem(s) and or how do I find out what's causing this?
I have zero knowledge of electronics, that probably won't help, but I would still like to give it a try :-)
djones
 
Posts: 1
Joined: Sun Feb 03, 2013 12:41 pm

Re: X0XB0X very low volume.

by drtitus on Mon Feb 04, 2013 5:56 am

I just had this problem today... for me it was solved by re-soldering the pins from the headphone chip (LA4140) and the BA6110 from the VCA. I was seeing the signal (using my oscilloscope) at pins 6,7, 8 on the BA6110, but the headphone output was very quiet. Check this thread: viewtopic.php?t=3954
drtitus
 
Posts: 6
Joined: Mon Dec 14, 2009 2:10 am

Re: X0XB0X very low volume.

by drtitus on Wed Feb 06, 2013 8:15 pm

Had been beating my head against the wall after the problem came back. Turned out it was a bad joint on one of the caps in the mixer section. Found it by probing around at each pad until I got a sporadic volume increase. By probing around I was able to make a connection between the leg of the component and the track which brought the thing to life. I wasn't seeing any output from pin 6 on the headphone amp, checked it was being powered correctly and then narrowed it down to "something on the input of the amplifier".

Good luck, be patient ;)
drtitus
 
Posts: 6
Joined: Mon Dec 14, 2009 2:10 am

Re: X0XB0X very low volume.

by synthplayer on Fri Feb 08, 2013 10:35 pm

djones wrote:I bought this defective X0XB0X on the web with the intent of fixing the unit.
So the issue it that the output volume is very very low.
Where do I go from here, what could be the problem(s) and or how do I find out what's causing this?
I have zero knowledge of electronics, that probably won't help, but I would still like to give it a try :-)


First, it would be worth a try to reheat the all the soldering joints in the synth section i.e. top half of the x0xb0x pcb and check J5 connection to the IO board pcb; to eliminate possible bad contact/dry joint issue.

If that doesn't help, then you can use a multimeter in AC mode to check for signal strength. You can program/play a pattern with a single note to keep the signal constant, have all the pot setting on the x0xb0x turned to minimum except the TUNE knob.

Check VCF for output
Measure with a meter in AC 20V mode or look on the CRO at R96 connecting C14

Check VCA for output
Measure with a meter in AC 20V mode or look on the CRO at C38 connecting to Volume pot.

You should get at least >1V at all of these points.
synthplayer
 
Posts: 20
Joined: Sat Dec 13, 2008 4:54 pm