Thanks guys !
There was something strange going on.... After writing my previous
mail I ran over a few components with a "freeze" spray, among them
the transistors and caps area of both VCOs on the problematic
oscillator and the R40 component (what looks like a mutli-leg
transistor but I guess is a multi-resistor ?)
Suddenly, two things happen (which still happen if I turn the machine
off for a few hours and back on... regardless internal temperature):
1. The bad oscillator is no more out of tune !
2. The entire scale has changed - i.e the gap between each note to
the one that follows it is larger (there is more than one octave gap
between C4 and C5 for example)
But that made me recall that when I got hte unit there was not tuning
issue at all, and the bad tuning problem on the second oscillator
only started once I started servicing the machine)
Strange huh ?
Could it be R40 that is defective ? does that make sense ?
Thanks again !
--- In
PolySix@yahoogroups.com, "Chromatest J. Pantsmaker"
<chromatest@g...> wrote:
>
>
>
> replace them again? Sometimes (and it will always bite you) you
put in a bunk part as a replacement.. then you spend all week looking
for something else, saying "it can't be X! I replaced X"..
>
>
> ----- Original Message -----
> From: gil_we <gil_we@y...>
> To: PolySix@yahoogroups.com
> Subject: [PolySix] Re: Trident MKII - one oscillator is out of tune
> Date: Tue, 06 Dec 2005 21:51:15 -0000
>
> >
> > You know what ?... now I relaize I replaced IC8 and ICx11 as
well !
> >
> > Any other idea you can think of ?
> >
> >
> >
> >
> > --- In PolySix@yahoogroups.com, Johannes Hausensteiner
<johau@g...>
> > wrote:
> > >
> > > If you already replaced Rx39/Cx10 then the only thing in common
> > > for both VCOs in one voice is ICx11 (TL072). THe value of Rx39
> > > is not very critical unless it is very different to the nominal
> > > value of 1k
> > >
> > > > By IC8 are you refering to ICx08 ? it's a 4558 opamp.
> > > No, I mean IC8, which is a 4051. It is common to all voices; it
> > > demultiplexes the CV for the VCOs
> > >
> > > Johannes
> > >
> > >
> > > gil_we wrote:
> > > > Thanks !
> > > > > The Cx10 and Rx39 have been already replaced to no avail.
> > > > > By IC8 are you refering to ICx08 ? it's a 4558 opamp.
> > > > > btw, I now see that I had to replace Rx36 with a slightly
> > different
> > > > value because even after the machine is warm enough, with the
> > > > original value the related VCO still cannot get tuned with the
> > other
> > > > oscillators, not matter how you set the VCO tuning trimmers.
> > > > > Thanks again.
> > > > > --- In PolySix@yahoogroups.com, Johannes Hausensteiner
> > <johau@g...>
> > > > wrote:
> > > > >>Hi,
> > > >>
> > > >>The caps are Cx10 ... where x is the voice number. On the
> > schematics
> > > >>only voice #7 is drawn in detail, so you can see C710. Maybe
it
> > is
> > > > > not
> > > > >>the cap but the accompanying resistor (R739), or the demux
(IC8).
> > > >>
> > > >>This is a great machine. Two really independant VCOs!
> > > >>
> > > >>Johannes
> > > >>
> > > >>
> > > >>gil_we wrote:
> > > >>
> > > >>>Thanks very much !
> > > >>>
> > > >>>The tuning is bad on both VCO1 and VCO2 of that oscillator >
>
> > > (although > >>>it seems more extreme on VCO2).
> > > >>>
> > > >>>I uploaded the schematics diagram for the VCO board to the
> > > files >>>section - what would be the caps to check on that one ?
> > > >>>
> > > >>>Thanks again.
> > > >>>
> > > >>>
> > > >>>--- In PolySix@yahoogroups.com, Johannes Hausensteiner > >
> > > <johau@g...> > >>>wrote:
> > > >>>
> > > >>>
> > > >>>>Hi,
> > > >>>>
> > > >>>>I only have the schematics for the MK I; which I do not
know > > whether
> > > > >>>>it is similar to the MK II. Which VCO has the problem? Is
it
> > VCO-
> > > > > 1 or
> > > > >>>>VCO-2 or both? If it is both then have a look at the hold
>
> > > > capacitors > >>>>after the VCO CV demux IC15 (a 4051) on
> > > KLM-301 board. These
> > are
> > > > > the
> > > > >>>>caps C25 - C32.
> > > >>>>
> > > >>>>Good luck,
> > > >>>>
> > > >>>>Johannes
> > > >>>>
> > > >>>>
> > > >>>>gil_we wrote:
> > > >>>>
> > > >>>>
> > > >>>>>I've been recovering this one, found in the flea market.
> > Overall
> > > > > it > >>>>>had about 8-9 different faults that I fixed,
> > > leaving two > > problems.
> > > > >>>>>The first is a bad SSM2056 chip which I need to find. The
> > second
> > > > > i > >>>>>probably inherent in the discrete ciruit of the
> > > second > > oscillator.
> > > > >>>>>Upon powering it up, that particular oscillator will be
> > > out of > > tune, > >>>>>till it gets to its max. internal
> > > temperature where the tuning > > of > >>>>>that VCO is geting
> > > more or less - stable.
> > > >>>>>
> > > >>>>>All other oscillators are immediately in tune, no matter
what
> > is
> > > > > the > >>>>>temperatue inside the machine.
> > > >>>>>
> > > >>>>>I, of course, tried to figure out what the bad component
is
> > > by >>>>>blowing with a straw on each and each of the suspected
>
> > > > compnents, but > >>>>>blowing on every component on the
circuit
> > > of that oscialltor > > which > >>>>>seems to be pitch related,
> > > seems to effect the pitch.
> > > >>>>>
> > > >>>>>I also tried to switch transistors between the bad
> > > oscillator > > and > >>>>>another (working one) but the problem
> > > persisted.
> > > >>>>>
> > > >>>>>Does anyone have any other idea / direction ?
> > > >>>>>
> > > >>>>>Thanks
> > > >>>>>
> > > >>>>>
> > > >>>>>
> > > >>>>>
> > > >>>>
> > > >>>>
> > > >>>>
> > > >>>
> > > >>>
> > > > > > > > > > > > PolySix "Digiest" Page:
> > > http://www.acc.umu.se/~amber/Poly6 > Yahoo! Groups Links
> > > > > > > > > > >
> > >
> >
> >
> >
> >
> >
> >
> >
> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6
> > Yahoo! Groups Links
> >
> >
> >
> >
>
>
>
> .sig
> -Chromatest J. Pantsmaker
> http://www.chromatest.net
>