[sdiy] CA3130 problem solved ->> S&H problem now

[Gert Jalass]

Hi Rutger & all,

I did follow this discussion with a small smile on my lips and was asking 
myself why nobody did consider that the schematic is incorrect ( by accident 
or by intention ) ?

Just to remind about the hassle people will get into when building the 911 
(Moog EG) where one condensator has been deliberately dropped in the 
schematic ...

Considering the 2002 :

The PCB does reveal a patch wire - i.e. the connection between (4) of the CA 
3140 (!) and GND has been cut and instead connected to (4) of RC 4531 (!) .

Enjoy Xmas
Gert

----- Original Message ----- 
From: "Rutger Vlek" <rutgervlek at hotmail.com>
To: <uzs159 at uni-bonn.de>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, December 22, 2005 1:25 AM
Subject: Re: [sdiy] CA3130 problem solved ->> S&H problem now


> Hi René
>
> your were right about the offsetting. I made the R7 modification you 
> suggested, and that helps. I removed the offsetting at the input Op-Amp, 
> but i'm confused what to do about the output op-amp. How do i get the same 
> scaling as with the input??
>
> Greetings,
>
> Rutger
>
>
>>From: René Schmitz <uzs159 at uni-bonn.de>
>>To: Rutger Vlek <rutgervlek at hotmail.com>
>>CC: synth-diy at dropmix.xs4all.nl
>>Subject: Re: [sdiy] CA3130 problem solved ->> S&H problem now
>>Date: Thu, 22 Dec 2005 01:30:06 +0100
>>
>>Hi Rutger and all,
>>
>>I don't know if this has anything to do with your problem, but what I find 
>>strange about this schematic is the way in which the FET is turned on and 
>>off. A positive drain will cut off the FET just as a negative gate. I'd 
>>say that R7 should go to between the output of U1-D and the Gate of Q1. 
>>Maybe I'd make it a bit larger than 10k.  All that offsetting of the input 
>>and output would be unnecessary then. Besides that the biassing on the 
>>input depends on how you couple in the signal, if there is a cap on the 
>>output of the steering circuit, then its indeed Ub/2, if not then it'll be 
>>rather something like Ub/3.
>>
>>Cheers,
>>  René
>>
>>Rutger Vlek wrote:
>>>Haha, no, i didn't miss it. The person who couldn't get it to work was 
>>>me, i think. And if it wasn't me then i did miss it.
>>>
>>>I have built Ray's Single Chip sample and hold exactly according to the 
>>>schematic, except for the transistors MPF102. I couldn't find those and 
>>>replaced then with 2N5486 first and now i've tried the BF245C, but no 
>>>change... The problem is that my sample & hold doesn't trigger the "hold" 
>>>transistor right.
>>>
>>>What happens is as follows:
>>>
>>>-When the Sample Rate potmeter is turned completely to the left the CV at 
>>>the input is directly passed through to the output, without any change 
>>>(at least, that's what is sounds like. But it's possible that it's 
>>>resampled with a very high frequency, beyond my hearing capabilities).
>>>
>>>-When i turn the Sample Rate potmeter to the right suddenly the input 
>>>voltage at that moment is being held at the same level. You could say 
>>>that the "hold" is now working. But....for an indefinite periode.
>>>
>>>So that's the problem. All components seem to be the right ones, the only 
>>>difference with Ray's version is the transistors and:
>>>
>>>- two 3M resistors are 3M3 ones (but that shouldn't make the difference). 
>>>At least in the filter for the clock signal i calculated the frequency 
>>>difference between 3M3 and 3M and that's really a minor difference.
>>>
>>>- the 200pF clock capacitor (C2) is actually a 220pF. But again...no big 
>>>difference.
>>>
>>>I'm really stumped, what could cause this problem....
>>>
>>>Regards,
>>>
>>>Rutger
>>>
>>>>From: Ian Fritz <ijfritz at earthlink.net>
>>>>To: "Rutger Vlek" <rutgervlek at hotmail.com>
>>>>Subject: Re: [sdiy] CA3130 in Polyfusion Noise module...should a new 
>>>>one work?
>>>>Date: Wed, 21 Dec 2005 16:14:11 -0700
>>>>
>>>>Did you miss the recent post from someone who could *not* get it to 
>>>>work?
>>>>
>>>>At 03:28 PM 12/21/05, you wrote:
>>>>
>>>>>Anyway, i'm a happy man now. Next thing is getting the S&H to work. But 
>>>>>this should be ok since Ray Wilson designed it ;).
>>>>
>>>>
>>>
>>>
>>>
>>
>>--
>>uzs159 at uni-bonn.de
>>http://www.uni-bonn.de/~uzs159
>>
>>
>
>
>