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 Forum index » DIY Hardware and Software » YuSynth
VCA issues
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djfill



Joined: Jan 10, 2012
Posts: 26
Location: Cardiff, Wales, UK

PostPosted: Sun May 06, 2012 4:53 am    Post subject: VCA issues Reply with quote  Mark this post and the followings unread

Hello, I'm getting towards the finish-line of phase one of my project. I've built 5 oscillators, ARP filter, Mixer, ADSR but I'm really stuck on the VCA, one of the more simpler circuits.

I've started with taking voltages at some obvious points, but if someone could give me an idea of what I should be expecting at other points that would be a good start.

I've checked, double checked and triple checked the board and wiring but I can't see anything wrong. I've also replaced U1, U2, Q1,2 and 3. I initially built the DC version but added the components for the AC version in case that made a difference. There is a corner of the PCB that looks suspect, but I've added a link wire to the capacitor and checked for continuity around the board and it's ok.

So far I've made the following observations:

U1 pin 4 = -15.14V
U1 pin 8 = 15.4V
U1 pin 7 = -13.79V DC (this is my main cause for concern as i would expect a waveform to appear here?)
U2 pin 4 = -15.14V
U2 pin 7 = 15.4V


Cardiff-20120503-00241.jpg
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Board top side
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Cardiff-20120503-00242.jpg
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Board underside
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Cardiff-20120506-00254.jpg
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Input wave (2V per div)
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Cardiff-20120506-00256.jpg
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U1 pin 1 (2V per div)
 Filesize:  1.05 MB
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Cardiff-20120506-00256.jpg



Cardiff-20120506-00257.jpg
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Q1 base (10mV per div)
 Filesize:  1.09 MB
 Viewed:  74 Time(s)
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Cardiff-20120506-00257.jpg


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PHOBoS



Joined: Jan 14, 2010
Posts: 1884
Location: Moon Base
Audio files: 366

PostPosted: Sun May 06, 2012 5:28 am    Post subject: Reply with quote  Mark this post and the followings unread

just a quick observation, could be nothing but just in case.


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djfill



Joined: Jan 10, 2012
Posts: 26
Location: Cardiff, Wales, UK

PostPosted: Sun May 06, 2012 5:51 am    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
just a quick observation, could be nothing but just in case.


OMG!! That was it!!! Laughing

PHOBoS I can't thank you enough...I must go the opticians next...
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PHOBoS



Joined: Jan 14, 2010
Posts: 1884
Location: Moon Base
Audio files: 366

PostPosted: Sun May 06, 2012 6:02 am    Post subject: Reply with quote  Mark this post and the followings unread

great, glad I could help Very Happy
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