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

[Gil W.]

I see,

So basically the 22uf cards should have a little bit more of low end ?

I see 6 of them are 22uf while only 2 are 15uf. Should I just recap the 15uf to an "all 22uf" to match the other 6 ?

Or could it be that the rest components on the 15uf cards are different than the ones of the 22uf ?

I want to go for a full recap, they all look very old...


--------------------------------------------
On Tue, 3/29/16, Tom Wiltshire <tom at electricdruid.net> wrote:

 Subject: Re: [sdiy] OBXa cards uses either 15uf -or- 22uf caps ?!
 To: "Gil W." <gil_we at yahoo.com>
 Cc: synth-diy at dropmix.xs4all.nl, "Nils Pipenbrinck" <n.pipenbrinck at hilbert-space.de>
 Date: Tuesday, March 29, 2016, 11:31 AM
 
 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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