Sequential circuits samplers

That could be down to old voice chips or old capacitors in and around the voice chips or anything else beyond my technical knowledge. 
I have uploaded some photos.
http://groups.yahoo.com/group/prophet2000/photos/album/647889420/pic/list

In photo 1 there are some non-polar capacitors(black ones) In mine one just pulled straight off so I'll be replacing those.
In photo 4 it shows some TL084 op-amps (I think) these could be feeling a little tired in the resonance section?

With the ESQ-1 that uses the same voice chips it gives a value after calibrating, something like 4217,5129 etc and if they fall outside a certain value then I think it says to replace them in the service manual. 
With the P2K it seems we are without this luxury. 
Ideally you would want all voice chips to be of the same batch.




________________________________
 From: p r <pierre.ruiz1@...>
To: prophet2000@yahoogroups.com 
Sent: Monday, 25 February 2013, 17:39
Subject: Re: [prophet2000] Re: P2000 schematics/service manual
 

  
u could as well be right one never knows with those old things :)
problem is not all voices sound the same, i believe filters resonate (a lot) more on some than others, and to such an extent that there has to be a way to tune that, or something is not functioning correctly. But ive been busy with other synths lately and have yet to take a peep inside and check what the pcbs looks like, i am a tad surprised about what u say about there being no trim pots but as u say maybe it can be digitally done. Hence why i am curious about what could be in the manual about it. or maybe some CEMs are getting a little old...


On Sun, Feb 24, 2013 at 2:51 AM, cyllall <cyllall@...> wrote:

I don't think it is possible to tune the filters.There are no trimmers anywhere on the PCB.
>
>Tuning of samples is most likely done in the digital domain.
>
>There might be a filter calibration routine like in the Ensoniq ESQ-1 which tries to match resonance and cut-off values between voices so they sound similar at the same settings.This is either in a hidden menu(don't think so or there would need to be a storage system with battery to remember this setting) or it is done automatically on power up, or doesn't exist at all.
>
>There are capacitors with the CEM3379's that set how the filter behaves(I think) and if these are not at the correct values cut-off or resonance could be different between voices because of this, but this isn't the same as tuning.
>
>What is the problem actually?
>
>ps I could be wrong about all of this.
>
>
>
>--- In prophet2000@yahoogroups.com, p r <pierre.ruiz1@...> wrote:
>>
>> "It would just be nice to have a schem that can be read."
>> ditto.
>>
>> i need to tune the filters in mine, would appreciate if u could prioritise
>> that bit - but i don't want to selfishly deprive anyone else from other
>> parts if in deeper need.
>>
>>
>
>> On Fri, Feb 22, 2013 at 1:53 PM, Martin Ator <cyllall@...> wrote:
>>
>> >
>> >
>> > I've just picked up a broken P2K. I haven't opened it yet. I will get back
>> > to you if I get stuck. It would just be nice to have a schem that can be
>> > read. I would like to build my own ram expansion card too if the one I have
>> > is standard ram. The schems that are floating around aren't very clear.
>> >
>> > Cheers
>> > Martin
>> >
>> >
>> >   ------------------------------
>> > *From:* duncan <ferrograph@...>
>> > *To:* prophet2000@yahoogroups.com
>> > *Sent:* Friday, 22 February 2013, 12:35
>> > *Subject:* [prophet2000] Re: P2000 schematics/service manual
>
>> >
>> >
>> > I have it here in hard copy. it will take a while to scan it all. is there
>> > a part I could prioritise for you?
>> >
>> > --- In prophet2000@yahoogroups.com, "cyllall" wrote:
>> > >
>> > > Hi, Any news on the P2K schematic front?
>> > > Martin
>> > >
>> > > --- In prophet2000@yahoogroups.com, "duncan" wrote:
>> > > >
>> > > > folks- I have unearthed this manual from my collection, but it may be
>> > a while before I get it all scanned, PDF'd & uploaded.
>> > > > please bear with me.
>> > > >
>> > > > duncan.
>> > > >
>> > >
>> >
>> >
>> >
>> >
>> >
>> >
>>
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