Crumar Musical Instruments User Group.

I don't believe it! I left my Crumar Spirit standing on it's side near the
window for a day or two - the afternoon sun beaming down upon it's black
underbelly. But this isn't exactly the tropics, it's south west England.
Not really that hot (even at this time of year).

Yet, on completing tidying the studio up, returning the Spirit to it's
usual slot on the desk, the keyboard scanning doesn't seem to be doing
very much any more.

Sometimes when I power up there's a note there already (that you can't
change using the keyboard) and sometimes there is nothing until I hit a
key - and then you get a note that you can't subsequently change using the
keyboard.

Putting the arpeggiator in "ripple" mode, the Spirit just plays up its
entire range and then starts at the bottom again.

Any ideas where to start?

I have checked the basics like jumper cable connections, made sure no key
is shorting, etc. But, I don't really have much more than a multimeter to
probe around with. Any suggestions for homing in on the fault would be
great, before I resort to professional servicing.


Thanks and regards,
Matt Nolan.

Here's a bit of an update:

I've traced the pitch CV path back through the DAC, the adder for the
arpeggiator and the keyboard scanning ICs.

I found that the keyboard scanning clock oscillator wasn't quite running
at the specified 20kHz, so I went and tweaked it (not that I guess this
should matter *too* much). The odd thing is, if I have my multimeter probe
on the oscillator output, everything works. However, if I then take the
probe off, you only get one more key press before the scanning stops
working again.

This is nothing to do with the extra loading perhaps detuning the osc, as
it runs over quite a wide range of frequencies. Strangely enough, the
multimeter probe trick only works if it is in frequency measuring mode!
Not in voltage measuring, or anything else! Peculiar!!

I can only guess that there's something slightly wrong with IC1 (the 40106
multi inverter chip used to form the oscillator), or IC5 (the 4081 multi
AND gate chip) that generates all sorts of other signals, on the keyboard
PCB, P-1016.

The "OSC RUN" signal is high, so that shouldn't be stopping the
oscillator. Hmm, I think I'll have to check if that diode 41 is OK.

Any clues anyone?

Cheers,
Matt Nolan.
--
Chief Knob Twiddler - Teeth Records
               Bath - UK

Update: Replacing IC5, a CMOS 4081 quad AND gate fixes the keyboard
scanning problem.

However, something is still not quite right. I think. The arpeggiator is
as it always has been since I've had the Spirit - it seems to do just what
it should except when you hold down 3 keys in "leap" mode - I get 3 notes
arpeggiated, not the 9 I would expect. The octave jumping isn't working.
Strange.

The other thing, which I'm not sure is a fault or not, but I'm fairly sure
it didn't used to behave like this. In regular (non arpeggio) operation,
the last note keyed priority is a bit funny. If you hold 1 note and then
add and take away a second, you get the second while it is pressed and it
returns to the 1st when you release the second. Fine. But if you are
holding 2 or more, toggling a 3rd doesn't return you to either of the
first 2, the VCO stays with the last note. Is this how it is supposed to
work?

I've replaced practically all the digital ICs in there now, but only IC5
made a difference. I need to get my hands on a 40174 and a 4517 to check
ICs 6 and 7 though. If it's neither of those, then I'm off hunting caps,
diodes and dry joints again...


Regards,
Matt Nolan.

Matt,

Both problems you describe (last keyed priority fails to return with three
or more keys down, and
three note leap fails to jump octaves) are present in my Spirit as well, so
I would assume that you've
identified bugs or anomalies in the design.

I'm glad to hear that you're back up and running.

-alex

  -----Original Message-----
  From: mattn@... [mailto:mattn@...]On Behalf Of
Matt Nolan
  Sent: Wednesday, July 10, 2002 11:23 AM
  To: vintagesynthrepair@yahoogroups.com; crumar@yahoogroups.com
  Subject: [crumar] Re: Help with Crumar Spirit


  Update: Replacing IC5, a CMOS 4081 quad AND gate fixes the keyboard
  scanning problem.

  However, something is still not quite right. I think. The arpeggiator is
  as it always has been since I've had the Spirit - it seems to do just what
  it should except when you hold down 3 keys in "leap" mode - I get 3 notes
  arpeggiated, not the 9 I would expect. The octave jumping isn't working.
  Strange.

  The other thing, which I'm not sure is a fault or not, but I'm fairly sure
  it didn't used to behave like this. In regular (non arpeggio) operation,
  the last note keyed priority is a bit funny. If you hold 1 note and then
  add and take away a second, you get the second while it is pressed and it
  returns to the 1st when you release the second. Fine. But if you are
  holding 2 or more, toggling a 3rd doesn't return you to either of the
  first 2, the VCO stays with the last note. Is this how it is supposed to
  work?

  I've replaced practically all the digital ICs in there now, but only IC5
  made a difference. I need to get my hands on a 40174 and a 4517 to check
  ICs 6 and 7 though. If it's neither of those, then I'm off hunting caps,
  diodes and dry joints again...


  Regards,
  Matt Nolan.

  Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Alex Iles wrote:

> both problems you describe (last keyed priority fails to return with three
> or more keys down, and
> three note leap fails to jump octaves) are present in my Spirit as well, so
> I would assume that you've
> identified bugs or anomalies in the design.

Interesting. Can anyone else confirm this? I'm wondering if it's an
inherent design fault, or a very common thing to go wrong due to age?

Ta,
Matt.