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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
VCS fall/rise rate knob range
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roman_f



Joined: Jul 03, 2007
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PostPosted: Thu Dec 29, 2011 7:13 pm    Post subject: VCS fall/rise rate knob range
Subject description: why so short
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is that normal that my VCS rise/fall rate knobs operate only in a small range?
say 5-7 on the dial makes the whole knob movement

thanks
roman
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Mongo1



Joined: Aug 11, 2011
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PostPosted: Sun Jan 01, 2012 11:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

That doesn't seem right.

I've built the DUSG, which is similar, and it's knobs operate over a very wide range. It sounds like there must be something wrong somewhere.

Gary
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roman_f



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PostPosted: Thu Jan 05, 2012 7:31 am    Post subject: Reply with quote  Mark this post and the followings unread

please take a look at the scan of the pcb, maybe i did some mistake...


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Mongo1



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PostPosted: Thu Jan 05, 2012 7:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Roman,

I don't know much about this one. I went over the CGS Support Group on Yahoo and asked for help over there. Maybe someone will drop by that knows more than I do about this.

Gary
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janvanvolt



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PostPosted: Thu Jan 05, 2012 8:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Will also look into this, however i have the original VCS.
One first question: Which Pots do you use ? Lin / Log ?

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roman_f



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PostPosted: Thu Jan 05, 2012 9:43 am    Post subject: Reply with quote  Mark this post and the followings unread

many thanks, gary :)

janvanvolt wrote:
Will also look into this, however i have the original VCS.
One first question: Which Pots do you use ? Lin / Log ?


A10K on rise/fall rate
and B50K on rise/fall cv
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The Bad Producer



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PostPosted: Thu Jan 05, 2012 10:11 am    Post subject: Reply with quote  Mark this post and the followings unread

In the pic you posted there is a wire link missing between the FCW and SWF pads (top rightish area on board), I can't see my boards, I think this is for power to the TL074... But I guess you've already soldered that in maybe?
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roman_f



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PostPosted: Thu Jan 05, 2012 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

yes, since i have 6 boards here - the one which is wired sure has all the links

i just scanned the spare one
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Mongo1



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PostPosted: Thu Jan 05, 2012 11:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
yes, since i have 6 boards here


Based on this and some other things we've talked about, I think you must be building the largest synth ever seen! Do you have a specific plan in mind, or are you just making it up as you go?

Gary
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The Bad Producer



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PostPosted: Thu Jan 05, 2012 11:55 am    Post subject: Reply with quote  Mark this post and the followings unread

roman_f wrote:
yes, since i have 6 boards here - the one which is wired sure has all the links

i just scanned the spare one


I thought so! Only things I could suggest - as per usual Very Happy is wiring, connections, soldering - you know the score! Also I remember mine acting oddly depending on how the trimmer was set (ie not working at all, being weird), though I don't remember that having anything to do with the controls...? The only other thing that has been a common issue with these is the pinouts of the transistors, but you would have noticed that for sure from all the other VCS problem threads! Again probably not relevant!

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otherunicorn



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PostPosted: Thu Jan 05, 2012 2:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've looked over your photo, and apart from that link, I can't see anything obviously wrong.
The value and type of pots used will actually have very little effect. They are not critical. My guess would be the transistors. Either you have the two types swapped, or you have got them from a manufacturer that uses a non standard pinout. If you have a transistor tester in your multimeter, put a new transistor from the same batch into it, and check. When the transistor is in the correct way, it will have a gain/Hfe in the 100's. If it is in backwards, the gain will be very low - probably under 20. I have seen circuits that manage to "work" even with all the transistors in backwards.

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roman_f



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PostPosted: Sun Jan 08, 2012 8:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

otherunicorn wrote:
I've looked over your photo, and apart from that link, I can't see anything obviously wrong.
The value and type of pots used will actually have very little effect. They are not critical. My guess would be the transistors. Either you have the two types swapped, or you have got them from a manufacturer that uses a non standard pinout. If you have a transistor tester in your multimeter, put a new transistor from the same batch into it, and check. When the transistor is in the correct way, it will have a gain/Hfe in the 100's. If it is in backwards, the gain will be very low - probably under 20. I have seen circuits that manage to "work" even with all the transistors in backwards.


i will do that after the sleep, thank you for the tip!
though all the components are from elby kits

upd: as i've soldered all 6 kits - i think i have to desolder those transistors to check. won't be easy, as the wires are short.
do you think if the pinout may vary from different manufacturers?

Last edited by roman_f on Sun Jan 08, 2012 10:02 pm; edited 1 time in total
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roman_f



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PostPosted: Sun Jan 08, 2012 9:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Mongo1 wrote:
Quote:
yes, since i have 6 boards here


Based on this and some other things we've talked about, I think you must be building the largest synth ever seen! Do you have a specific plan in mind, or are you just making it up as you go?

Gary


dear Gary, 5 of those VCSs are going to be for sale in MU-format
i've discussed that with Ken and it it seems he's ok with that

i want to keep my 5U system pretty small now - my wooden case is 64U, but i will use only 2 rows of it now (instead of 4). other rows are for keeping some small boxes like drum-machines. i've sold most of the filters and specific modules in december. let's see how it goes. i still remember your request about making panels - i'll do the guide when i get the new camera, my lovely ricoh gr1 was broken by a 2-years old son :)
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Mongo1



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PostPosted: Mon Jan 09, 2012 7:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
5 of those VCSs are going to be for sale in MU-format


Ah! That makes sense. Good idea!

Quote:
my lovely ricoh gr1 was broken by a 2-years old son Smile


Ouch.... Someone once told me that the reason children are so cute is to keep you from throwing them out a window. Laughing

Gary
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roman_f



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PostPosted: Mon Jan 30, 2012 8:06 am    Post subject: Reply with quote  Mark this post and the followings unread

dear ken
i've tried with 3906 - it's the gain is 230 when installed properly and 6 when reversed

roman
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