[sdiy] OBXa cards uses either 15uf -or- 22uf caps ?!

Tom Wiltshire tom at electricdruid.net
Tue Mar 29 11:31:39 CEST 2016


Probably not.

15uF+20% is 18uF, and 22uF- 20% is 17.6uF, and that's typical tolerances.

Although it seems weird, I agree with Nils, it's probably just they didn't have any 15uF and upgraded to the next-nearest part.

They're not all power bypass though - two are, but mostly they seem to be DC blocking caps between sections. There's a pair on each filter (in/out) and one after the VCA. Given that, the larger value will just push the bass response a little further down to the low end.

Tom


On 29 Mar 2016, at 01:03, Gil W. <gil_we at yahoo.com> wrote:

> Well, there are 7 of them on each card. Could all be "only" power bypass ? should there be any sonic difference between the two types of boards ?
> 
> 
> 
> --------------------------------------------
> On Tue, 3/29/16, Nils Pipenbrinck <n.pipenbrinck at hilbert-space.de> wrote:
> 
> Subject: Re: [sdiy] OBXa cards uses either 15uf -or- 22uf caps ?!
> To: synth-diy at dropmix.xs4all.nl
> Date: Tuesday, March 29, 2016, 1:23 AM
> 
> On 03/29/2016 12:41 AM,
> Gil W. wrote:
>> ok this one is strange.
>> 
>> I opened up an OBXa,
> and I can see that some voice board have all 15uf
> electrolytic caps, while on others they are all 22uf
> !
> 
> 
> The service manual lists these caps as
> 15µF.
> 
> Probably Oberheims
> part dealer run out of 15µF caps during production 
> and they just upped the value to the more
> common 22µF to keep going.
> 
> It's just the power bypass cap anyway, so
> the exact value does not make 
> much of a
> difference.
> 
> Best,
>    Nils
> 
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