you may be right. Although it's a matter of one bit corrupted to
dramatiacally change the sound - imagine altered MSB of filter sutoff.
If you try to call pathces from 1-8 and the sound is the same, that could
mean that your RAM is not responding, or CS line to it is broken. If the
patches differ, but everytime you recall them they are more or less not
changed, that means RAM is OK, but something is wrong with writing it. Maybe
WE trace broken.
You could also try to measure power supply current of the ram. This 4V you
mention is worrying me. If it's considerably high (like a few mA) it may
suggest that RAM is really broken, possibly by electrostatic discharge.
Another way of testing is is to measure RAM power supply voltage when the P6
is powered off. It should be only 0.2-0.3V lower than battery voltage. If
it's 0.7V or more, that's a sign that something is wrong with the RAM.
Roman
----- Original Message -----
From: "sputnik979" <sputnik979@yahoo.com>
To: <PolySix@yahoogroups.com>
Sent: Friday, June 30, 2006 11:17 AM
Subject: [PolySix] Re: Memory failure, S-RAM suspected.
> Hi !
> The case is that it is my tech who's doing all the dirty work ;) I'm
> just managing & providing insights, let's call it. He has schematics
> and he knows what he's doing; he replaced the bad SN chips and
> resoldered all the bad traces so that now all formerly dead functions
> like octave switching, subosc, ADSR, cutoff, attenuator work fine.
> Now he's sort of asking me what to do, because all the traces seem
> fine, and this one IC is diffferent from others in the way of keeping
> 4V. So we have a complementary cooperation here as you see ;)
> And the question of random patches/values:
> If I create let's say a deep bass patch and save it to a given
> location - the 'deep bass' is there, as long as you don't change
> presets... so the random stuff appears only when you come back to
> read out the patch. So I guess the values don't even make their way
> to the storage device?
>
>
>
>
> --- In PolySix@yahoogroups.com, "Roman" <modular@...> wrote:
> >
> > hi,
> > I don't think your RAM is damaged, try to find broken traces on the
> PCB
> > leading to it. If some of them are damaged by battery leakage,
> writing a
> > patch will actually write random stuff to the RAM, same thing when
> trying to
> > read a patch. It's OK for RAM to work at smaller voltage, because
> it's
> > powered via diode. Although I'd expect something like 4.5V and not
> 4.
> > It's hard to find replacement chip. I made a small adaptor, that
> takes
> > typical RAM and converts to TC5514 pinout, pictures included.
> > BTW, desoldering RAM can add more damage to the board if you're not
> > carefull. OTOH it can fix some problems if there was some
> intermitent
> > contact at some of the RAM leads.
> >
> > Roman
> >
> > ----- Original Message -----
> > From: "sputnik979" <sputnik979@...>
> > To: <PolySix@yahoogroups.com>
> > Sent: Tuesday, June 27, 2006 8:43 PM
> > Subject: [PolySix] Memory failure, S-RAM suspected.
> >
> >
> > > Hi folks!
> > >
> > > My Polysix after battery leakage had the typical symtomps you
> might
> > > expect.
> > >
> > > After having cleaned & resoldered the guts everything's fine
> apart from
> > > the memory;
> > > I create a patch, I press WRITE, I choose the location. Seems OK.
> But
> > > just click another patch, then come back to the one I just saved -
> and
> > > it's not there. A new 3.6V battery has been installed, but it is
> not
> > > the matter of battery, beacause we are talking about doing this
> when
> > > the synth is still operatnig, being plugged, so it has all the
> power
> > > needed all the time.
> > >
> > > I'm inclined to think the TC5514 S-RAM chip is the culprit,
> because all
> > > the chips keep voltage of 5V whereas this one has just 4V.
> > >
> > > What do you think ? What replacement part for TC5514 should I
> look for?
> > > I've heard about Intersil HM6514 and Nec uPD444c (D444C-6514) but
> are
> > > these really the only ones? I came across some chips
> with 'similar'
> > > characteristics and I really would like to avoid importing the
> above
> > > mentioned ICs.
> > >
> > > I'm not a tech, but a tech's opinion would be greatly appreciated
> and
> > > helpful.
> > >
> > > cheers
> > > aero
>
>
>
>
>
>
>
> PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6
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