Yes, the sample and hold buffers were all checked and replaced. That was the first place we started when trying to diagnose the problem. I don't think it is them. Basically every chip except for the EPROMs has been swapped out with a chip known to work. All of the RAM ICs were shuffled and we did a hard reset. (Everything erased.) I wouldn't have thought it was the EPROMs either, but here we are. :) I can't think of many other things that it could be. This unit also has certain notes that will suddenly play at 100% velocity out of the blue, but only about 5% of the time. Swapping out every IC did not take care of that either.
________________________________
From: John Leimseider <leimseiderj@...>
To: chromapolaris@yahoogroups.com
Sent: Wednesday, October 5, 2011 3:42 PM
Subject: RE: [chromapolaris] Re: Tuning/Channel Problems?
EPROMs fail VERY rarely… I’ve never seen one fail in a Polaris.
It’s way more likely to be in a sample and hold… Have you scoped the output of
the S/H to see if there’s any unusual crud? It’s usually a distorted sawtooth
when it’s bad. Use your scope on AC coupling and crank the input…
John Leimseider
Electronics Technician/Technicien des
instruments électroniques
Cantos Music Foundation/National Music Centre Project/Projet du
Centre National de Musique
Second Floor, 134 – 11 Ave SE, Calgary AB T2G 0X5
Phone/ Téléphone: (403) 543-5127
Fax/ Télécopie: (403) 543-5129
www.cantos.ca/www.nmc.ca<http://www.cantos.ca/www.nmc.ca>
Coming up at Cantos
September 24 – Pub Songs & Singalongs for the Legacy Children’s Foundation
The Lions aren’t showing signs of slowing down! The final
Calgary gig of the year is at Cantos for a double album release and doing good
by helping with an instrument drive for The Legacy Children’s Foundation.
8:00pm, tickets available online.
September 25 – All That Jazz Brunch at Thomsons Restaurant
A new jazz series at the Hyatt Regency Calgary. Enjoy a variety of
dynamic jazz perfomances the last Sunday of the month for the All That Jazz
Brunch. The John Gray Trio performsat Thomsons Restaurant. 11:00am.
Hear that? The National Music Centre will give Canada a place that
amplifies the love, the sharing and the understanding of music at the historic King
Edward Hotel in the heart of downtown Calgary’s revitalized East Village.
The final NMC renderings have been revealed. Play your part and view the
building renderings at http://www.nmc.ca <http://www.nmc.ca>
From:chromapolaris@yahoogroups.com [mailto:chromapolaris@yahoogroups.com] On
Behalf Of rob
Sent: Wednesday, October 05, 2011 1:27 PM
To: chromapolaris@yahoogroups.com
Subject: [chromapolaris] Re: Tuning/Channel Problems?
I had another non-working Polaris in the shop so I swapped the chips between
the 2 Polari and was able to kill two birds with one stone. I swapped out all
of the chips from a polaris that doesn't boot up into the one with the channel
1 tuning problem. I did not swap the EPROMs, but I did switch all of the RAM
chips around in the working one and did a full reset. The tuning problem
persisted. I swapped out the DAC with a dac from a Polaris that works
perfectly, and the tuning problem persisted. At this point, the only thing I
have not swapped out is the EPROMs themselves. As a side benefit, I was able to
confirm that all of the chips in the non working Polaris actually worked as
well(except for the EPROM) and I think I am arriving at the conclusion that the
EPROMs are bad in both units. Each unit has has a new 186 processor put in, and
has been recapped. There's not much left to be the problem aside from perhaps a
flux issue, though the board looks very clear of flux.
If anyone thinks there is something I might not have considered, please let me
know. Thanks!
-Rob
--- In chromapolaris@yahoogroups.com,
Rob Currier <robiecurrier@...> wrote:
>
> I'm going to pull the DAC from my OB8 to confirm that's the problem, then
I will let you know if I need one. Â More soon. Â Thanks.
> -ROb
>
>
> ________________________________
> From: synthparts <synthparts@...>
> To: chromapolaris@yahoogroups.com
> Sent: Sunday, October 2, 2011 11:47 PM
> Subject: [chromapolaris] Re: Tuning/Channel Problems?
>
>
> Â
> If you do need a new DAC I have one.
> Doug
> synthparts.com
> --- In chromapolaris@yahoogroups.com,
"John Leimseider" <leimseiderj@> wrote:
> >
> > I'd check the buffers for the 4051 first. I've also seen more than
the normal failure of the DACs. When they lose a really low order bit, certain
voices won't tune, just a matter of what voltages are needed for the autotune.
I have a couple of spares... The same ones that are in the OB8... Same symptom,
sometimes.
> >
> > See if the good voices are getting really accurate octaves.
> >
> >
> >
> > John Leimseider
> >
> > Electronics Technician/ Technicien des instruments électroniques
> >
> >
> >
> >
> >
> >
> > Cantos Music Foundation/National Music Centre Project/Projet du
Centre National de Musique
> > Second Floor, 134 - 11 Ave SE, Calgary AB T2G 0X5
> > Phone/ Téléphone: (403) 543-5127
> > Fax/ Télécopie: (403) 543-5129
> > www.cantos.ca/www.nmc.ca <http://www.cantos.ca/www.nmc.ca>
<http://www.cantos.ca/www.nmc.ca <http://www.cantos.ca/www.nmc.ca>
>
> > Coming up at Cantos
> >
> > September 24 - Pub Songs & Singalongs for the Legacy Children's
Foundation
> >
> > The Lions aren't showing signs of slowing down! The final Calgary gig
of the year is at Cantos for a double album release and doing good by helping
with an instrument drive for The Legacy Children's Foundation. 8:00pm, tickets
available online.
> >
> > September 25 - All That Jazz Brunch at Thomsons Restaurant
> >
> > A new jazz series at the Hyatt Regency Calgary. Enjoy a variety of
dynamic jazz perfomances the last Sunday of the month for the All That Jazz
Brunch. The John Gray Trio performsat Thomsons Restaurant. 11:00am.
> >
> > Hear that? The National Music Centre will give Canada a place that
amplifies the love, the sharing and the understanding of music at the historic
King Edward Hotel in the heart of downtown Calgary's revitalized East Village.
The final NMC renderings have been revealed. Play your part and view the
building renderings at http://www.nmc.ca <http://www.nmc.ca> <http://www.nmc.ca <http://www.nmc.ca>
>
> >
> >
> >
> >
> >
> > From: chromapolaris@yahoogroups.com [mailto:chromapolaris@yahoogroups.com]
On Behalf Of rob
> > Sent: Thursday, September 29, 2011 4:39 PM
> > To: chromapolaris@yahoogroups.com
> > Subject: [chromapolaris] Re: Tuning/Channel Problems?
> >
> >
> >
> >
> >
> > I experienced this issue as well. I still have not figured out what
the cause is. I replaced the 4051's, swapped out CEMs from other voices,
replaced the electrolytics, and still cannot make voice one tune. It seems to
be happening to both oscillators on voice 1, so this is something affecting the
CV coming from the DA I am guessing. Perhaps the offset calculations happening
on the 4051s could be wrong? Does anyone have any ideas as to what else this
might be?
> > -Rob
> >
> > --- In chromapolaris@yahoogroups.com <mailto:chromapolaris%40yahoogroups.com> , "Paul D. DeRocco"
<pderocco@> wrote:
> > >
> > > > From: charlespjackson
> > > >
> > > > Recently I began to experience an issue with my Polaris
going out
> > > > of tune. Upon doing some research and reviewing older posts
here
> > > > regarding similar problems it appears that the culprit has
been
> > > > narrowed down to a faulty Channel (1). If I manually
disable
> > > > this channel then the Polaris functions and stays in tune
just fine.
> > > > From what I've gathered so far it seems the problem might
be some
> > > > bleeding and/or bad (Sample & Hold) caps?
> > > > I would just like to know if I'm accurately diagnosing the
> > > > problem and if so how intricate/expensive a fix this may
be? Are
> > > > the parts necessary for such a fix available? Where might I
be
> > > > able to locate them?
> > >
> > > I think it's usually the 4051 analog switches that leak. They're
pretty easy
> > > to find, since they're near the left end of each channel, which
are the six
> > > step-and-repeat sections on the right half of the board.
> > >
> > > This is a pretty easy thing to diagnose and fix, for anyone with
a scope and
> > > good soldering skills. You can tell if a S&H is leaking by
looking at the
> > > op-amp outputs (pins 1, 7, 8 and 14 of the nearby TL084/LF347
parts) and
> > > seeing if there's any sawtooth modulation larger than a few
millivolts.
Show quoted textHide quoted text
> > >
> > > --
> > >
> > > Ciao, Paul D. DeRocco
> > > Paul mailto:pderocco@
> > >
> >
>
