Yamaha CS80

Hi, writing here for a friend's CS80.
My friend found a strange problem: when he does set the ringmod's speed at full with modulation at full , the sound coming from the modulator is quite hearable : the fact is that this sound you can hear even without playing anything on the keyboard; same problem happens with the SubOScillator: when he sets the speed at full, the sound can be heard without any key pressed.
I believe there must be something wrong with some preamps in OE1 board or PRA's muting FETs, my idea is to look at R51/52 to see if is there any faulty resistor concerning the Suboscillator.

Anyway I'm looking for your savvy advices.
Thx for any reply.
M

[Non-text portions of this message have been removed]

I believe I also hear some leakage from my RM circuit....
-----Original message-----
From: "Max Fazio" faxiomas@...
Date: Mon, 09 Jun 2008 02:47:54 -0600
To: yamahacs80@yahoogroups.com
Subject: [yamahacs80] problem: audible modulations at no playing.

Hi, writing here for a friend's CS80.
My friend found a strange problem: when he does set the ringmod's
speed at full with modulation at full , the sound coming from the
modulator is quite hearable : the fact is that this sound you can hear
even without playing anything on the keyboard; same problem happens
with the SubOScillator: when he sets the speed at full, the sound can
be heard without any key pressed.
I believe there must be something wrong with some preamps in OE1 board
or PRA's muting FETs, my idea is to look at R51/52 to see if is there
any faulty resistor concerning the Suboscillator.

Anyway I'm looking for your savvy advices.
Thx for anyreply.
M

[Non-text portions of this message have been removed]




[Non-text portions of this message have been removed]

I just tried it with headphones and the volume cranked. It's definitely
there, but pretty low level. It's not surprising since the RM and the
output pre-amps are both on the PRA board. I noticed that the pre-amp
ICs already have RC coupling on their power supply pins. Maybe
calibrating the RM and pre-amp would help.

I don't hear any Sub Oscillator bleeding to the outputs on the unit I have.

David

Laurie Curry wrote:

> I believe I also hear some leakage from my RM circuit....
> -----Original message-----
> From: "Max Fazio" faxiomas@...
> Date: Mon, 09 Jun 2008 02:47:54 -0600
> To: yamahacs80@yahoogroups.com
> Subject: [yamahacs80] problem: audible modulations at no playing.
>
> Hi, writing here for a friend's CS80.
> My friend found a strange problem: when he does set the ringmod's
> speed at full with modulation at full , the sound coming from the
> modulator is quite hearable : the fact is that this sound you can hear
> even without playing anything on the keyboard; same problem happens
> with the SubOScillator: when he sets the speed at full, the sound can
> be heard without any key pressed.
> I believe there must be something wrong with some preamps in OE1 board
> or PRA's muting FETs, my idea is to look at R51/52 to see if is there
> any faulty resistor concerning the Suboscillator.
>
> Anyway I'm looking for your savvy advices.
> Thx for anyreply.
>

Hi David
To specify the problem, the suboscillator can be "heard" also at low frequency because of a strong noise component and, strangely, even without any modulation amount to anything; even stranger is the fact that this effect can be heard on R output only , while the L goes pretty steady about it.
The ringmodulator is a different story: the effect can be heard on both channels, loud enough to tell it's not natural, moreover , if you turn "modulation" at full you can hear a strong amount of background noise; I'm beginning to think it can be one of ringmod's 1452 pre-amps which has gone fishing.
Any suggestion about it? Thx for your reply...
M

----- Original Message -----
From: David Rogoff
To: yamahacs80@yahoogroups.com
Sent: Tuesday, June 10, 2008 5:54 AM
Subject: [yamahacs80] Re: problem: audible modulations at no playing.


I just tried it with headphones and the volume cranked. It's definitely
there, but pretty low level. It's not surprising since the RM and the
output pre-amps are both on the PRA board. I noticed that the pre-amp
ICs already have RC coupling on their power supply pins. Maybe
calibrating the RM and pre-amp would help.

I don't hear any Sub Oscillator bleeding to the outputs on the unit I have.

David

Laurie Curry wrote:
> I believe I also hear some leakage from my RM circuit....
> -----Original message-----
> From: "Max Fazio" faxiomas@...
> Date: Mon, 09 Jun 2008 02:47:54 -0600
> To: yamahacs80@yahoogroups.com
> Subject: [yamahacs80] problem: audible modulations at no playing.
>
> Hi, writing here for a friend's CS80.
> My friend found a strange problem: when he does set the ringmod's
> speed at full with modulation at full , the sound coming from the
> modulator is quite hearable : the fact is that this sound you can hear
> even without playing anything on the keyboard; same problem happens
> with the SubOScillator: when he sets the speed at full, the sound can
> be heard without any key pressed.
> I believe there must be something wrong with some preamps in OE1 board
> or PRA's muting FETs, my idea is to look at R51/52 to see if is there
> any faulty resistor concerning the Suboscillator.
>
> Anyway I'm looking for your savvy advices.
> Thx for anyreply.
>





[Non-text portions of this message have been removed]

Hi Laurie
I too believe that a bit of effect could spring up because of background noise, it's always a 30 year old analog monster, here though the effect is unnaturally loud...
M

----- Original Message -----
From: Laurie Curry
To: yamahacs80@yahoogroups.com
Sent: Tuesday, June 10, 2008 5:38 AM
Subject: Re: [yamahacs80] problem: audible modulations at no playing.


I believe I also hear some leakage from my RM circuit....
-----Original message-----
From: "Max Fazio" faxiomas@...
Date: Mon, 09 Jun 2008 02:47:54 -0600
To: yamahacs80@yahoogroups.com
Subject: [yamahacs80] problem: audible modulations at no playing.

Hi, writing here for a friend's CS80.
My friend found a strange problem: when he does set the ringmod's
speed at full with modulation at full , the sound coming from the
modulator is quite hearable : the fact is that this sound you can hear
even without playing anything on the keyboard; same problem happens
with the SubOScillator: when he sets the speed at full, the sound can
be heard without any key pressed.
I believe there must be something wrong with some preamps in OE1 board
or PRA's muting FETs, my idea is to look at R51/52 to see if is there
any faulty resistor concerning the Suboscillator.

Anyway I'm looking for your savvy advices.
Thx for anyreply.
M

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]

i do have a slight background noise when not playing, although its not too problematic really.

another thing i notice, that im wondering if anyone else sees, is i occasionally get a wierd VERY high pitched noise when playing chords on certain patches. it sounds like a buildup of very high harmonics or something. this only showed itself after the full recap of the M-boards and PRA board.


[Non-text portions of this message have been removed]

Ringmodulator
When I set the rm's modulation-slider at max, there's some small
increase of noise (like white noise etc), the speed setting has no
effect and can not be heard.

Sub osc:
when I select saw up, saw down, pulse or noise, I can hear the lfo
when I set the speed and vcf-destionation-slider at max. Vca- and vco
slider settings have no effect.
However, when trying this I noticed that the lfo-speed could be heard
as triggers at my left output. This disappeared when I opened up the
panel. My guess is that it was caused by the multicable that runs at
the right side. During the past 30 years, it has bended the PRA-board
a bit to the left. Either the cable caused some crosstalk itself with
the PRA-board or it caused the PRA to crosstalk with it's neighbour,
OE2. Everytime you close the panel, the cable will rest in a slightly
different position. Still, the SUB-board it miles away from all this
so I guess it must be the multicable. You never know with this
synth...

--- In yamahacs80@yahoogroups.com, "Laurie Curry" <laurie@...> wrote:
>
> I believe I also hear some leakage from my RM circuit....
> -----Original message-----
> From: "Max Fazio" faxiomas@...
> Date: Mon, 09 Jun 2008 02:47:54 -0600
> To: yamahacs80@yahoogroups.com
> Subject: [yamahacs80] problem: audible modulations at no playing.
>
> Hi, writing here for a friend's CS80.
> My friend found a strange problem: when he does set the ringmod's
> speed at full with modulation at full , the sound coming from the
> modulator is quite hearable : the fact is that this sound you can
hear
> even without playing anything on the keyboard; same problem happens
> with the SubOScillator: when he sets the speed at full, the sound
can
> be heard without any key pressed.
> I believe there must be something wrong with some preamps in OE1
board
> or PRA's muting FETs, my idea is to look at R51/52 to see if is
there
> any faulty resistor concerning the Suboscillator.
>
> Anyway I'm looking for your savvy advices.
> Thx for anyreply.
> M
>
> [Non-text portions of this message have been removed]
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>
>
>
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