Low volume / low voltages at IC15B

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FLOz
 
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Joined: Tue Oct 09, 2012 2:13 pm

Low volume / low voltages at IC15B

Post by FLOz »

Hello!

I ordered this kit from x0xsh0p.de a few month ago. At the beginning the output volume was really low (needs +24dB in Logic to hear something) and suddenly it worked and the volume was OK during one month. But now I got back the same issue: it's time to debug.

Situation:
VCF: output OK (headphone test)
VCA: output is low on the volume's pot. So I guess the issue is located in the VCA and actually the voltages on IC15B are not correct on its outputs:

Pin1: 5.31V
Pin2: 5.31V
Pin3: 0V
Pin4: 0V without note playing / varying between 0,1 to 1V in random mode
Pin5: 0V
Pin6: 0.66V
Pin7: 0.66V
Pin8: 0.66V
Pin9: 11.86V

I have about 5V less as normal on the outputs. Is it a bad BA6110 or should I check something else?

Many thanks for your support.

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antto
 
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Joined: Thu Apr 15, 2010 3:21 pm

Re: Low volume / low voltages at IC15B

Post by antto »

pin 6, 7, and 8 are along the output signal

is your BA6110 soldered nicely? maybe check that and/or re-heat the legs

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mmm
 
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Joined: Tue Apr 24, 2012 1:51 am

Re: Low volume / low voltages at IC15B

Post by mmm »

Pins 6 and 7 are connected anyway.

Pin 6 is the output of the actual VCA while pin 7 is the input for the following output buffer (for which the output then would be pin 8).

Since the VCA and the output buffer are operated from a single side supply instead of a bi-polar supply they need a DC offset to work properly. Obviously this DC offset is missing on pins 6 and 7; and so it is no surprise that it is also missing on pin 8.
The question now is if this comes from IC15B pulling down the DC offset or if it is missing altogether. The DC offset is generated from the 5.33V supply and involves R162, C40 and R127 to R129. Maybe it helps to check around those components

FLOz
 
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Joined: Tue Oct 09, 2012 2:13 pm

Re: Low volume / low voltages at IC15B

Post by FLOz »

I checked the section with R162, C40, R127 and R129: I got a resistance value of 54K between the 5,3V supply and the pin 7 of IC15B that is correct according to my calculation (R = R162 + ((R127+R129)*R128/(R127+R129+R128)). Unfortunately I can't check the capacitor C40.

I removed the BA6110 (it is on a socket) and I got 5,05V on the pin7 (instead of 0,66V when BA6110 is inserted). It looks like the BA6110 is pulling down the output voltages.

Could a bad BA6110 do that?

Thanks for your support.

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mmm
 
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Joined: Tue Apr 24, 2012 1:51 am

Re: Low volume / low voltages at IC15B

Post by mmm »

FLOz wrote: I removed the BA6110 (it is on a socket) and I got 5,05V on the pin7 (instead of 0,66V when BA6110 is inserted). It looks like the BA6110 is pulling down the output voltages.

Could a bad BA6110 do that?
Yes, I think so. Imagine a short to ground - this would pull down this part of the circuit.

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profête
 
Posts: 32
Joined: Sat Jun 29, 2013 9:50 pm

Re: Low volume / low voltages at IC15B

Post by profête »

MMM wrote:
FLOz wrote: I removed the BA6110 (it is on a socket) and I got 5,05V on the pin7 (instead of 0,66V when BA6110 is inserted). It looks like the BA6110 is pulling down the output voltages.

Could a bad BA6110 do that?
Yes, I think so. Imagine a short to ground - this would pull down this part of the circuit.

hello

have you solved your problem please?

had you low level in MIXOUT but high in PHONE please ? i have this problem

thanks

FLOz
 
Posts: 4
Joined: Tue Oct 09, 2012 2:13 pm

Re: Low volume / low voltages at IC15B (solved)

Post by FLOz »

Hello,

I received today a spare of BA6110 from x0xsh0p and it solved my issue. It was once again a bad BA6110.

Thanks everyone for your support.

FLOz
 
Posts: 4
Joined: Tue Oct 09, 2012 2:13 pm

Re: Low volume / low voltages at IC15B

Post by FLOz »

ProFête wrote:
MMM wrote:
FLOz wrote: I removed the BA6110 (it is on a socket) and I got 5,05V on the pin7 (instead of 0,66V when BA6110 is inserted). It looks like the BA6110 is pulling down the output voltages.

Could a bad BA6110 do that?
Yes, I think so. Imagine a short to ground - this would pull down this part of the circuit.

hello

have you solved your problem please?

had you low level in MIXOUT but high in PHONE please ? i have this problem

thanks
Headphone and MIX OUT were both low.

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profête
 
Posts: 32
Joined: Sat Jun 29, 2013 9:50 pm

Re: Low volume / low voltages at IC15B

Post by profête »

Headphone and MIX OUT were both low.
ok thank

i have make a new topic, and checked voltage, help is welcome :

http://forums.adafruit.com/viewtopic.ph ... 19#p206719

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