Yamaha CS80

Hi David,

These adjustments might well be the very same ones I tried a while ago using an oscilloscope - and for the life of me I couldn't get those waveforms shown in the service manual, to show on my scope!

In the end I gave up... maybe now we can get to the bottom of what needs sorting there? I think Kent might know? We could all do with an updated 'filter envelope set-up procedure' page I think...;c)

Cheers,
TOM



--- In yamahacs80@yahoogroups.com, rj krohn <r_j_d_2.phila@...> wrote:
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> wish i could help. i tried to do some very minute EG calibrations by ear once on my 80. wasnt working. (luckily got it close enough to be not noticable). best of luck!
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> --- On Tue, 2/1/11, David Rogoff <david@...> wrote:
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> From: David Rogoff <david@...>
> Subject: [yamahacs80] Need help calibrating envelope generators on CS80!
> To: yamahacs80@yahoogroups.com
> Date: Tuesday, February 1, 2011, 12:06 AM
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>       Hi all.
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> I've been working on a CS80 for a bit now and finally have it all 
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> functioning to some degree.  I'm going through the full 
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> tuning/calibration procedure now
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> (http://therogoffs.com/cs80/CS80%20Adjustment%20Procedures%20and%20updates.PDF) 
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> and am having difficulty with the envelope times.  I've never tried this 
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> before.  On all units I've worked on, I've only needed to do the power 
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> supply and the usual M-card tuning.
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> However, this beast had some of its M-cards replaced from a very giving 
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> CS-60 and the EG times, filter cutoffs, and levels are really whacked 
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> out from board to board.  So, I'm trying to do the VCF Attack time on 
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> page 9 and VCA Attack time on page 15.  I came up with a nice trigger 
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> source: they specify a 3Hz square wave of +/-10v.  I found that tapping 
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> the output of the Sub-Oscillator square wave before its output resistor 
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> divider makes a great trigger. I just ran this, through a 1K resistor, 
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> to one input of my 'scope and then to the TR input of the M-card.  I 
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> trigger on this channel and then connect the specified EG testpoint to 
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> the other input of the 'scope.
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> This sort-of works, at least for the calibration of the short (4ms) 
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> time.  Triggering and observing signals this slow on an old, analog 
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> oscilloscope is a real pain.  Again, I got it somewhat stable for the 
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> 4ms measurement. However, for the 125ms measurement, I don't have a 
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> prayer. With the low repeat rate and long time measurement, the display 
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> is too erratic to get any useful measurements. At work I have access to 
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> nice digital HP/Agilent 'scopes that can do this in their sleep, but I 
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> don't really want to bring the CS80 to work!  What did Yamaha intend to 
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> be used for this measurement back in 1976?  I guess an old analog 
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> storage 'scope would have worked, but those were pretty rare.
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> Anyway, I'd appreciate any tips from folks who have (successfully) tried 
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> this!
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> By the way, since I've had to pull the M-cards out to do the full 
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> calibration, for tuning I've been able to grab the sine wave right off 
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> the wave shape converter chip at pad CP1.   I run this into one input of 
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> my 'scope and my iPhone, running Cleartune (in pitch-pipe mode with sine 
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> wave) into the other 'scope input and set it to X-Y mode.  Beautiful 
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> Lissajous patterns that make it a snap to tune!  Of course, since the 
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> cards are out, the temperature isn't quite right and I'll have to do a 
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> final tweak when it's all put back together. For that I'll use the 
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> excellent iStrobesoft strobe tuner app from Peterson. It's $10, but well 
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> worth it, especially since a hardware strobe tuner from Peterson start 
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> at $100 and go up to $800!
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> Thanks again,
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> David
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