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

[Rutger Vlek]

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 ;).
>