x0xb0x newbie: Problems with VCA BA6110 pin 4
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Re: x0xb0x newbie: Problems with VCA BA6110 pin 4

by MMM on Sat Oct 06, 2012 6:07 am

mex wrote:I just tested your suggested route, which does the dc offset:

R162 - R128: brings the correct 5,33 V where it should be and cuts it down to 0,7 Vafter R128, I guess this is right, but there could be a error at least.


It definitely is not right. You need to have over 5 volts after R128. My guess is that a defective BA6110 is pulling the voltage down.

Remove the BA61100 and measure if you get the 5.33 volts on the solder pads for pin 6 und 7.
MMM
 
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Re: x0xb0x newbie: Problems with VCA BA6110 pin 4

by mex on Sun Oct 07, 2012 6:11 am

hmm but it should work as a voltage divider network, no?

And it only makes the offset of the Amplifier output and since my whole circuit is kind of working I assume the BA6110 is not broken, although its electrics and everything impossible could be reality ( from my expirience : ))

Now I got the box home and I am working with it, as I posted yesterday, I did switch the resistor divider before Q31 to 2k2 and 600 Ohm ( before it was 2k2 and 220k ) so I did change it really dramatically, which also tells me that still something should be faulty but hey it works, and until now no other solution is in sight , so I take it :)

Soldering my BA6110 out is kind of a problem since intelligent me thought there are usually no problems with ICs, so I soldered in in directly without a pullable connector :(

So I think I wont touch it for a while.

Greets
mex
 
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Re: x0xb0x newbie: Problems with VCA BA6110 pin 4

by MMM on Sun Oct 07, 2012 7:56 am

mex wrote:hmm but it should work as a voltage divider network, no?


Yes and no.

Technically it works as a voltage divider indeed, HOWEVER:
We need to calculate the inner impedance of the BA6110 here as well. And that is probably high. If I'm not mistaken the buffer actually is to change the impedance of the output to low impedance.
The measurements on working xoxboxes show very little voltage drop which hints at an impedance in the megaohm range. Your measurements point more towards low kiloohms.

mex wrote:And it only makes the offset of the Amplifier output and since my whole circuit is kind of working I assume the BA6110 is not broken, although its electrics and everything impossible could be reality ( from my expirience : ))


Is it really working? Or is the output somewhat clipped? Have you checked with a scope?
MMM
 
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Re: x0xb0x newbie: Problems with VCA BA6110 pin 4

by mex on Mon Oct 08, 2012 4:50 am

I got my x0x at home without any measurment equipment doind patterns and tracks, everything works pretty good.

I got some clipping when playing some, but only some accented notes ( at least I do think so ) and only because you just did tell me so.

I think I will work with my x0x now, having in mind that something could break down, perhaps also the first linear voltage regulator, becasue the BA6110 may draw too much current, but I do not have another BA6110 to test right now.
So my x0x homemade project is ok, for now. Perhaps I will need your help again in couple of month when it stops working, for the mentioned reasons.

Next thing in my mind i building a SID synth from µCapps, if you know about this.

Thanks again.
mex
 
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