VCF is sleeping...
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VCF is sleeping...

by exagonal on Mon Mar 18, 2013 3:49 pm

Hi all! I have problems to VCF section, exactly no sound, though it is completely normal output of the VCO. :roll:
Of precise I noticed that, referring to the voltages shown in this image that enclose, I strongly different values ​​with regard to the collectors of Q12, as well as Q13, Q15, and so on ... until Q22, where the voltage in the two emitters arrives only to 1.80V.
The situation regarding Q21 instead appears to regulate.
Any suggestions? Thanks in advance!
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Re: VCF is sleeping...

by synthplayer on Mon Mar 18, 2013 10:42 pm

It would be helpful if you could post the DCV of your VCF circuit, for Q9,10,11 to Q17 and Q22, Q23.
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Re: VCF is sleeping...

by MMM on Tue Mar 19, 2013 5:14 am

If I'm reading the description right then the problem could be at Q22. Still it would be nice to have the voltage readings for the complete filter ladder.
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Re: VCF is sleeping...

by exagonal on Tue Mar 19, 2013 11:08 am

Yep! Thank you both for your reply !
The situation of the voltage of Q9, Q10 and Q11 how about the rest of the circuit is ok, except the network that goes from Q12 to Q22.
To be precise, you can see in this picture, in red,the voltages detected by me.
Any suggestion ??
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Re: VCF is sleeping...

by MMM on Tue Mar 19, 2013 1:37 pm

Please measure the voltage on all 5 pins of Q22.
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Re: VCF is sleeping...

by exagonal on Tue Mar 19, 2013 5:19 pm

the voltage are :

C1 = C2 = 11.65
E1 = 1.80
B = 11.64
E2 = 1.80

The voltages are ok apart the two emitters that are 1.80 V
I just replaced Q22 and does not seem to change anything.
Al high volume i can hear some clicks in syncro with tempo...
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Re: VCF is sleeping...

by MMM on Tue Mar 19, 2013 5:24 pm

What's the code for Q22 (both for the old and the new one)?
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Re: VCF is sleeping...

by exagonal on Tue Mar 19, 2013 5:57 pm

The writing is enough faded, I seem to see one " 89C " and the other " 19C "...you think they are defective?
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Re: VCF is sleeping...

by MMM on Tue Mar 19, 2013 6:05 pm

exagonal wrote:The writing is enough faded, I seem to see one " 89C " and the other " 19C "...you think they are defective?


They're not defective - they are probably fakes. The theory is that those are re-labeled 1583 or something similar. There had been numerous "89C" fakes and "59C" fakes (but I must admit that I'm hearing of a "19C" fake for the first time). You can try to check with a transistor tester if this the case; the 2291 has a common base and the 1583 a common emitter.
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Re: VCF is sleeping...

by exagonal on Tue Mar 19, 2013 6:17 pm

Damn it! This is quite annoying! I think at this point that he had fallen into a scam ... it is the only component that I purchased separately from the rest of the kit .... how can I be sure that it is a relabeled 1583? Rapid measurement which do you recommend?
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Re: VCF is sleeping...

by exagonal on Tue Mar 19, 2013 6:28 pm

Yes, I just got confirmation ... I run comparison measurements between the 1583 and this fake 2291 getting the same results .. in case I can inform you not to buy these items on E-bay from "hkutsource"
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Re: VCF is sleeping...

by exagonal on Tue Mar 19, 2013 6:35 pm

Thank you MMM
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Re: VCF is sleeping...

by MMM on Tue Mar 19, 2013 7:01 pm

exagonal wrote:Yes, I just got confirmation ... I run comparison measurements between the 1583 and this fake 2291 getting the same results .. in case I can inform you not to buy these items on E-bay from "hkutsource"


This doesn't have to be malice on the seller's part; he might have picked up a batch from someone else without knowing. This has happened in the past.

Just a quick comparison for measurements:

2SC2291 is ECBCE
2SC1583 is BCECB

(both are NPN). So, using the typical transistor check/HFE measurement built into most multimeters one can check both single transistors.
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Re: VCF is sleeping...

by exagonal on Sun Mar 31, 2013 3:48 pm

Sorry but I have to give you another fake-code that could represent false-C2291. In fact, unfortunately for my bad luck, I stumbled upon other false, they show the 94G code that accompanies the classic 2SC2291.
I hope this can help someone else! Where can I find the real 2291 ? Thank you for every little hint...
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Re: VCF is sleeping...

by antto on Sun Mar 31, 2013 3:54 pm

We are here too: irc.freenode.net >>> #x0xb0x
..:: c0nb0x v1.00 ::.. http://forums.adafruit.com/viewtopic.php?f=7&t=29282 (new control app - win/osx)
VCO Tuning: http://forums.adafruit.com/viewtopic.php?f=12&t=24759 (do it the EASY way)
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