help xoxbox volume problems

[blake]

Hi there,

I'm wondering if anyone has some advice troubleshooting a volume problem with a willyzx kit that I've built.

Specifically everything seems to be working normally, except that the volume is very low coming from both the headphone and mix outputs.

I've checked the voltages on the ba6110 thinking that might be the problem (I assume its the amp chip). The readings VDC readings that I got on each pin were very similar to the ones the testing faq said to expect:

pin 1: 5.3v
pin 2: 5.3v
pin 3: 0v
pin 4: 0v
pin 5: 0v
pin 6: 5.03 (should be 5.3v)
pin 7: 5.03 (should be 5.3v)
pin 8: 5.34
pin 9: 11.89

The VAC readings however were vastly different than the expected values noted in the faq

pin 1: 10.7v (should be 10mv)
pin 2: 10.7v (should be 0mv)
pin 3: 0v (should be 0mv)
pin 4: 0v (should be 1.2v)
pin 5: 0v (should be 0mv)
pin 6: 9.7v (should be 750mv)
pin 7: 9.7v (should be 750mv)
pin 8: 10.9v (should be 750mv)
pin 9: 25.3v (should be 0v)

Does anyone have any idea what problem this would indicate, besides a shot ba6110?

Thanks.

[aminoacid]

i dont know how picky thoose voltages are on pin 6 and pin 7. if that is the problem it should be cause of a bad or wrong resistor:

r162
r127
r128
r129

otherwise, if the chip was having an internal short, you would prob not see thoose other correct values.

do you have a scope?

try alos connect an external synth/machine into the mix in jack and see how volumes are out of mix out and phones out.

if thoose also are off, your problem might be further downb the line (mixer part for ex).

[guest]

sometimes inexpensive meters dont read vac right

check the volume on the resonance pot

[blake]

Unfortunately I don't have a scope at the moment, i suppose the vac levels are a bit low for budget meters to pick up properly...

I tried running a signal through the mix in and it came through on the mix out just as low as the xoxbox output, so the problem appears to be downstream of the vca. Incidentally, the signal was good at the resonance pot.

I'll move on down to the mixer section.

Thanks.

[guest]

did you find the full voltage map in the forums
its useful for checking sections

[blake]

I was able to correct the problem.

I made a pretty silly mistake and got transistors q33 and q34 mixed up.

Fortunately I had spares of each and swapped them out. Everything seems to be working correctly now.

Thanks for the help in narrowing down the location of the problem.