Vintage Synth Repair

Yep, really strange I have to agree. It was connected correctly and it was working correctly only in the -13-17V range.

I would love to find the schematics for this synth but seems like they are not available (this synth is quite rare).

Thanks,
Mikael

--- In vintagesynthrepair@yahoogroups.com, Hugh Vartanian <bouncev@...> wrote:
>
> Sounds like you have solved the regulator problem; no idea why the other
> part didn't work, assuming it was installed ok.  Strange to have a
> defective part like that.
> 
> I deleted the rest of the thread; post a link to the schematics if you
> still need some thoughts on the other issues.
> 
> Hugh
> 
> 
> On Fri, May 24, 2013 at 5:14 AM, Mikael <wmc_mick@...> wrote:
> 
> > **
> >
> >
> > The input voltage to the 7912 regulator is -22.2V. I replaced the new
> > regulators with the old ones (made by Texas Instruments), I now have
> > -12.25V as output for the 7912. I measured the voltages at the pins. The
> > new 7912 was a L7912ACV.
> >
> > --- In vintagesynthrepair@yahoogroups.com, Hugh Vartanian <bouncev@>
> > wrote:
> > >
> > > On the regulator problem, what is the input voltage to the 7912? More
> > > importantly, what are you using for a ground reference? Measure right at
> > > the regulator terminals, in and out, to its ground pin. Neg 14.xx volts
> > > might be a result of a loose ground floating positive a bit when power is
> > > applied. Remove power and the positive current draw and the 'ground'
> > > makes its way back to ground..... Just a thought.
> > > -Hugh
> > > On May 19, 2013 5:36 AM, "Mikael" <wmc_mick@> wrote:
> > >
> > > > **
> > > >
> > > >
> > > > Hi all!
> > > >
> > > > I bought a rare Crumar Composer I while ago but it has some problems.
> > This
> > > > synth has a mono synth section, a poly synth section, a organ section
> > and a
> > > > string section. All these sections can be combined. There is a separate
> > > > output for every section and a main output. The separate outputs work
> > but
> > > > the volume for the main output and the main output itself do not work,
> > > > could this be a problem in an amp-sircuit or something?
> > > >
> > > > The problem I'm trying to look at now and ask about is an issue with
> > the
> > > > poly synth section. The problem is that the attack for the envelope is
> > VERY
> > > > slow, I can change the attack rate on the front panel pot but the
> > fastest
> > > > attack is about 15 seconds. Can anybody give me a hint where to look
> > for
> > > > the problem? Also there is a pop when I release the key on all keys it
> > > > seems. The envelope of the poly-synth section is generated by a CEM3310
> > > > chip. There are also CEM3320 and 3330 chips on the poly section.
> > > >
> > > > Last problem I'm having is that the release rate for the organ section
> > is
> > > > very sensitive, it seems that the effective range is about 30 degrees
> > > > (1-1.5 on a scale from 1-10), if I turn the pot about 40 degrees I
> > have a
> > > > VERY long release time.
> > > >
> > > > I would really like to get this synth in shape, it sounds so good and
> > it's
> > > > very rare, I think Crumar made only 500 of these.
> > > >
> > > > Thanks in advance!
> > > >
> > > >
> > > >
> > >
> >
> >  
> >
>