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CS80 woes after storage

 

Hi CS80 gurus, owners and fans.?

I have a CS80 with Kenton midi that I have owned since 2012 and recently put into storage for three years. The synth was working fine prior to storing but now there are a range of strange, possibly interconnected, issues. I’ll try and describe yhem
as best I can.?
?
On powering up a single octave plays whatever keys you press on the keyboard. ?For instance no matter what C key that I press it’s all the same octave etc.?
?
The LFO doesn’t seem to work at all and the aftertouch brightness high and low paddle causes a pitch change.

maybe most telling when a select some preset buttons a random third button will light.?

Weirdly, at one stage I held the ribbon at a particular spot and was able to play the synth more or less normally.?

There may be more weirdness that I’m yet to discover but these are the main symptoms. I’m reasonably techy and have a scope but it would be great to get some ideas of where to start.
?
?
?
 

Those are some weird issues. As always, step 1 is to verify power. Use a meter to check for voltage and ripple or better yet use a scope.

+15, -15,?+10.6, -6.5,?+8.5 should all be pretty close. If so, move on. If not, you found where to start! :)

On Sat, Apr 12, 2025 at 8:38?PM Nigel99 via <nigel=[email protected]> wrote:
Hi CS80 gurus, owners and fans.?

I have a CS80 with Kenton midi that I have owned since 2012 and recently put into storage for three years. The synth was working fine prior to storing but now there are a range of strange, possibly interconnected, issues. I’ll try and describe yhem
as best I can.?
?
On powering up a single octave plays whatever keys you press on the keyboard.? For instance no matter what C key that I press it’s all the same octave etc.?
?
The LFO doesn’t seem to work at all and the aftertouch brightness high and low paddle causes a pitch change.

maybe most telling when a select some preset buttons a random third button will light.?

Weirdly, at one stage I held the ribbon at a particular spot and was able to play the synth more or less normally.?

There may be more weirdness that I’m yet to discover but these are the main symptoms. I’m reasonably techy and have a scope but it would be great to get some ideas of where to start.
?
?
?
 

Thinking about this some more and the way it's behaving, it sounds like the Kenton board may be the problem.

It's hard to imagine a non-Kenton unit displaying those mannerisms?and all of the items you called out are related to Kenton functions.

Maybe try pulling and re-seating all the Kenton board connectors.


On Sun, Apr 13, 2025 at 12:59?PM Scott Rodriguez via <synthrodriguez=[email protected]> wrote:
Those are some weird issues. As always, step 1 is to verify power. Use a meter to check for voltage and ripple or better yet use a scope.

+15, -15,?+10.6, -6.5,?+8.5 should all be pretty close. If so, move on. If not, you found where to start! :)

On Sat, Apr 12, 2025 at 8:38?PM Nigel99 via <nigel=[email protected]> wrote:
Hi CS80 gurus, owners and fans.?

I have a CS80 with Kenton midi that I have owned since 2012 and recently put into storage for three years. The synth was working fine prior to storing but now there are a range of strange, possibly interconnected, issues. I’ll try and describe yhem
as best I can.?
?
On powering up a single octave plays whatever keys you press on the keyboard.? For instance no matter what C key that I press it’s all the same octave etc.?
?
The LFO doesn’t seem to work at all and the aftertouch brightness high and low paddle causes a pitch change.

maybe most telling when a select some preset buttons a random third button will light.?

Weirdly, at one stage I held the ribbon at a particular spot and was able to play the synth more or less normally.?

There may be more weirdness that I’m yet to discover but these are the main symptoms. I’m reasonably techy and have a scope but it would be great to get some ideas of where to start.
?
?
?
 

Hi Scott, thanks for your input.
?
I'll verify the PSU today. I suspected the Kenton board as well and removed the board and the issues are the same.? I've checked the installation for shorts or wiring issues and it all seems fine. It was installed by Kent and i've had no issues with the midi or the synth in 10 years.
?
In it's current state the CS80 is not responding to LFO or SUB OSC aftertouch controls from it's own keyboard but if I trigger notes over midi these functions are working.? It's a real head-scratcher.
?
I'm wondering about the possibility of a failed IC or diode in the preset panel that could be sending mixed signals or failure in the BA board.?
?
I'm trying not to go straight into freak-out mode and suspect a YM26XX IC but it's hard with this many seemingly unrelated issues.??
 

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Hi Scott,

I have had a more thorough going over it and here is the symptom list:

Drone single note when midi board installed with analog in/out ribbon connected to Kenton board. All keys play the same note no matter what key is pressed. Same result both via midi and CS80 Keyboard.

If analog in/out connector is removed from Kenton midi board notes play in a single octave no matter what key is pressed from both over midi and the CS80 keyboard. The octave resets at each D key. ?The result is the same with the Kenton board removed completely.

Glissando is on full no matter how the controls are adjusted.

LFO and Sub OSC controls have no affect but will trigger over midi with the in/out ribbon from the CS80 removed from the Kenton board.

Moving the aftertouch paddles causes a pitch sweep of a few octaves or so, depending on the paddle movement. Paddle down and pitch is higher and paddle up makes the pitch of whatever note is playing, lower.?
Depending on paddle position the pitch change is not noticeable e.g. brilliance paddles up there is no pitch sweep but when the level paddles are at middle position notes can be heard. I’m assuming that they scale out of hearing range when the Level paddles are fully down as I can’t hear anything.

All of that makes it very hard to actually understand what is going on with the synth. With short attack a blip will play but sometimes a single note will sustain randomly here an there. It seems like the Attack slider is controlling the sustain time.

Mostly if I place a finger on the pitch ribbon I get a random crazy high or low note but in some cases I get a clean note that if I hold my finger in place on the pitch ribbon, with my other hand I can play the synth normally with chords and everything and mostly in tune. Should I play an 8 note chord, it will sound within the realm of decent and in tune.

I’m losing my mind. If anyone else feels these issues look familiar please drop me line. It would be much appreciated.?




On 14 Apr 2025, at 3:09?am, Scott Rodriguez via groups.io <synthrodriguez@...> wrote:

Thinking about this some more and the way it's behaving, it sounds like the Kenton board may be the problem.

It's hard to imagine a non-Kenton unit displaying those mannerisms?and all of the items you called out are related to Kenton functions.

Maybe try pulling and re-seating all the Kenton board connectors.

On Sun, Apr 13, 2025 at 12:59?PM Scott Rodriguez via <synthrodriguez=[email protected]> wrote:
Those are some weird issues. As always, step 1 is to verify power. Use a meter to check for voltage and ripple or better yet use a scope.

+15, -15,?+10.6, -6.5,?+8.5 should all be pretty close. If so, move on. If not, you found where to start! :)

On Sat, Apr 12, 2025 at 8:38?PM Nigel99 via <nigel=[email protected]> wrote:
Hi CS80 gurus, owners and fans.?

I have a CS80 with Kenton midi that I have owned since 2012 and recently put into storage for three years. The synth was working fine prior to storing but now there are a range of strange, possibly interconnected, issues. I’ll try and describe yhem
as best I can.?
?
On powering up a single octave plays whatever keys you press on the keyboard.? For instance no matter what C key that I press it’s all the same octave etc.?
?
The LFO doesn’t seem to work at all and the aftertouch brightness high and low paddle causes a pitch change.

maybe most telling when a select some preset buttons a random third button will light.?

Weirdly, at one stage I held the ribbon at a particular spot and was able to play the synth more or less normally.?

There may be more weirdness that I’m yet to discover but these are the main symptoms. I’m reasonably techy and have a scope but it would be great to get some ideas of where to start.
?
?
?
 

Argh... please disregard my last message. Your were onto it - the midi board was the source of a bunch of those issues.
?
I received the Kenton install instructions and now I know that traces and wires were cut to do the install which caused some crazy behaviour when the kit was removed.
?
A major fault does remain - the Keyboard control brilliance and level controls are causing a pitch input. I can dial in a fairly reasonable pitch and play the CS80 close to normally but outside that 'sweet spot' range is a load of dissonant shreaking that eventually goes out of hearing range as the paddles are at maximum.
?
Thanks for your help, Scott. I was mulling it over all day and the coin finally dropped to have a closer look at the midi install.
 

I repaired a CS60 once that showed bizarre pitch issues, where controls that weren't expected to affect pitch actually did cause pitch drifts. In this case the cause was that the grounds between the various power supplies had become disconnected from each other, and so the the power rails were all just floating around relative to each other. There was a single point at a bolt/screw on the housing where all the various grounds came together, and some of the wires near that connection had broken (I assume due to vibration/handling in this case).
?
jkjelec

On 04/14/2025 6:18 AM EDT Nigel99 <nigel@...> wrote:
?
?
Argh... please disregard my last message. Your were onto it - the midi board was the source of a bunch of those issues.
?
I received the Kenton install instructions and now I know that traces and wires were cut to do the install which caused some crazy behaviour when the kit was removed.
?
A major fault does remain - the Keyboard control brilliance and level controls are causing a pitch input. I can dial in a fairly reasonable pitch and play the CS80 close to normally but outside that 'sweet spot' range is a load of dissonant shreaking that eventually goes out of hearing range as the paddles are at maximum.
?
Thanks for your help, Scott. I was mulling it over all day and the coin finally dropped to have a closer look at the midi install.

 

Glad you found the issue!

I've installed a couple of those boards and I add quick disconnects (or connects as the case may be) and a set of instructions that allows the user or a tech to quickly remove the board for debugging.

I think Kenton should do something similar, especially given the very expensive midi board they sell for what it is, but they do leave it up to the customer.?


On Mon, Apr 14, 2025 at 6:18?AM Nigel99 via <nigel=[email protected]> wrote:
Argh... please disregard my last message. Your were onto it - the midi board was the source of a bunch of those issues.
?
I received the Kenton install instructions and now I know that traces and wires were cut to do the install which caused some crazy behaviour when the kit was removed.
?
A major fault does remain - the Keyboard control brilliance and level controls are causing a pitch input. I can dial in a fairly reasonable pitch and play the CS80 close to normally but outside that 'sweet spot' range is a load of dissonant shreaking that eventually goes out of hearing range as the paddles are at maximum.
?
Thanks for your help, Scott. I was mulling it over all day and the coin finally dropped to have a closer look at the midi install.
 

Regarding the Keyboard Control issue, the outputs are very separate and very segregated from physical pitch voltage inputs downstream, so thinking about upstream...

On the large KAS board, are the IC4 and IC5 chips socketed? Those two 4050 chips pass pitch information to the KBC cards.?If they're?in sockets you can try removing them to see if the problem goes away.

The data lines coming out of those are ganged at the inputs to the Keyboard Control cards,?so if one of the KBC cards is pulling down or shorting digital data on the KAS through the 4050's, the other KBC would certainly feel the effect as well. Those data lines connect to CD4006 shift register chips on the KBC cards; if the 4006's on the KBC cards happen to be RCA chips, those are pretty notorious for going bad. Somewhere to look anyway.


On Mon, Apr 14, 2025 at 6:18?AM Nigel99 via <nigel=[email protected]> wrote:
Argh... please disregard my last message. Your were onto it - the midi board was the source of a bunch of those issues.
?
I received the Kenton install instructions and now I know that traces and wires were cut to do the install which caused some crazy behaviour when the kit was removed.
?
A major fault does remain - the Keyboard control brilliance and level controls are causing a pitch input. I can dial in a fairly reasonable pitch and play the CS80 close to normally but outside that 'sweet spot' range is a load of dissonant shreaking that eventually goes out of hearing range as the paddles are at maximum.
?
Thanks for your help, Scott. I was mulling it over all day and the coin finally dropped to have a closer look at the midi install.
 

Hi Scott, I've socketed and replaced the 4050 chips but the KB control problem persists (it may have helped with the ribbon pitch issue as i'm not noticing that now).
?
I'll swap out the 4006s when I lay my hands on some and report back.
?
A heartfelt "thanks" for your help and pointing a novice in the right direction. Cheers mate!
?
P.S. It's not for the faint of heart in there.
 

What I mean is, remove the IC4 & IC5 chips completely and then power on the synth without those chips on the KAS board. Does the problem still persist??


On Tue, Apr 15, 2025 at 3:56?AM Nigel99 via <nigel=[email protected]> wrote:
Hi Scott, I've socketed and replaced the 4050 chips but the KB control problem persists (it may have helped with the ribbon pitch issue as i'm not noticing that now).
?
I'll swap out the 4006s when I lay my hands on some and report back.
?
A heartfelt "thanks" for your help and pointing a novice in the right direction. Cheers mate!
?
P.S. It's not for the faint of heart in there.
 

The issue persists without the 4050 chips.
?
Here is a video of the issue if you care to watch. Hard to hold the camera and play so don't expect Stanley Kubrick.
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It may be hard to tell from this small snippet of the problem but the pitched tone it seems to either raise up? - or down in pitch until out of hearing range.
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