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Dead Keys are Stuck in Arp

Dead Keys are Stuck in Arp

2018-04-19 by jhatzia@gmail.com

Hello,


I'm working on a Polysix repair project. I've replaced the unit with a new KLM-367 clone CPU board and it sprung the whole unit back to life except there are about 7 dead keys throughout the keybed. Oddly enough, those same notes are playing while the arp is engaged. Has anyone come across this? Sounds like an issue around the key assigner board. Also the while Chord Memory is engaged I get a hanging note as I depress any key.


Thanks.

Re: [PolySix] Dead Keys are Stuck in Arp

2018-04-19 by Florian Anwander

Ar those keys in one row? Or are they distributed over the keyboard?
If you tell us exactly which ones are affected, we might deduct from it
the cause. Start counting with #1 at the left end. (don't tell us the
note name. It does not matter in the electronical sense.)

Am 19.04.2018 um 17:08 schrieb jhatzia@gmail.com [PolySix]:
> except there are about 7 dead keys throughout the keybed. Oddly
> enough, those same notes are playing while the arp is engaged. Has
> anyone come across this? Sounds like an issue around the key assigner
> board. Also the while Chord Memory is engaged I get a hanging note as
> I depress any key.
> __._,_

--
http://www.florian-anwander.de

Re: [PolySix] Dead Keys are Stuck in Arp

2018-04-19 by jhatzia@gmail.com

The keys are spread between the keyboard (C#0, A0 F1, C#1, A2, F3, C#4, G4, A4, A#4). I can double check these once I'm home and get you exact note numbers.

Re: [PolySix] Dead Keys are Stuck in Arp

2018-04-20 by <backshall1@bellsouth.net>

He said C#0, A0, F1, C#1, A2, F3, C#4, G4, A4, A#4, which would be every 8 notes, except for the G4 and A#4. The G4 and A#4 may just be bad contacts. The others (any C#, A, F) is every eighth note and could indicate a bad wire to the keyboard, or a bad trace or diode on the matrix circuit board under the keys where the contacts are, or a problem on the KLM-366 between the keyboard connector (CN04) and the chips it connects to, or a problem on one of those chips. That is quite a few possibilities. I guess the real clues would be the fact that the arpeggiator does recognize that the key has been pressed even though it makes no sound when the arpeggiator is not engaged, and the strange statement that there is a “hanging note” when using Chord Memory. More details are needed on that. For the wiring to the keyboard, you would need to carefully inspect a disassembled key contact board to see which wire in the matrix is connected to all C#, A and F keys.
Don Backshall
 
Sent: Thursday, April 19, 2018 5:27 PM
Subject: Re: [PolySix] Dead Keys are Stuck in Arp
 
 

Hello,

Are you thinking a section of the rubber contacts under the keys are not working?

Sent from my iPhone

Re: [PolySix] Dead Keys are Stuck in Arp

2018-04-20 by backshall1@bellsouth.net

Replied to this a half hour ago via email and it never showed up, so I'll try again directly from the group conversation. Maybe you will get two of these. Maybe nobody will ever see it. Isn't Yahoo fun?

He said C#0, A0, F1, C#1, A2, F3, C#4, G4, A4, A#4, which would be every 8 notes, except for the G4 and A#4. The G4 and A#4 may just be bad contacts. The others (any C#, A, F) is every eighth note and could indicate a bad wire to the keyboard, or a bad trace or diode on the matrix circuit board under the keys where the contacts are, or a problem on the KLM-366 between the keyboard connector (CN04) and the chips it connects to, or a problem on one of those chips. That is quite a few possibilities. I guess the real clues would be the fact that the arpeggiator does recognize that the key has been pressed even though it makes no sound when the arpeggiator is not engaged, and the strange statement that there is a “hanging note” when using Chord Memory. More details are needed on that. For the wiring to the keyboard, you would need to carefully inspect a disassembled key contact board to see which wire in the matrix is connected to all C#, A and F keys.
Don Backshall

Re: Dead Keys are Stuck in Arp

2018-04-20 by jhatzia@gmail.com

Thank you Don- you really nailed describing my situation. I'm working on it again now. And was trying to reply to your comment to get a new description on the hanging note but it started working again..?

After leaving the synth on for a while I couldn't even get Chord Mem or Hold buttons to react. After cycling the power they reacted again but had hanging notes.. I was then pressing all the key assign buttons and after some clicks it started behaving properly... Now all those dead notes are playing fine (except the last G, A & A# are still very dead).. Very odd. I wouldn't be surprised if it happens again. I'm still unsure where a fault like that would be found in the circuit.

Well- I still have to install about 3 new button cap holders and clean the volume pot, so I would be surprised if the issue arises again, if it does I'll make sure to update this thread.


Re: Dead Keys are Stuck in Arp

2018-04-20 by jhatzia@gmail.com

And sure enough it's back in a stuck state and those same keys aren't responding.. So odd. So here's what I've discovered.

-When I first got the synth some screws were missing from the KLM-371 and board that holds the key assign buttons. 
-I then added some screws to the left side of the this board just under the arp and key assign buttons and now I just realized, if I loosen one of the screws the hanging notes stop. Very, very odd that this board being screwed in all the way will cause some of the keys to stop working and hang them in the arp.

The board now hangs a little loose but works, when screwed in all the way it causes the mentioned keys to stop reacting and get locked into the arp and sometimes the chord memory or poly mode too. 

My apologies as this is a bit of a phenomena and but I feel like I'm getting close.

Re: Dead Keys are Stuck in Arp

2018-04-20 by backshall1@bellsouth.net

The delays in these messages are hilarious. My first reply by email was sent at 8:37 pm EDT. It showed up on the web page maybe an hour later. Even the message sent directly through the web site took half an hour to show up on the web site.
Anyway, if the keys problem is intermittent like that, it's probably a bad connection on CN04. Not tight or corroded or something. Or possibly a bad solder joint where that wire connects to the contact board. As for the G4, A4, A#4, they do not share any common wire. They are all on the last rubber strip of contacts though. Clean the gold contacts on the circuit board and the carbon contacts on the rubber strip. If there is a real problem with the Key Assign Mode switches, that is a whole other matrix on the panel board. Then again it might be just bad connections on CN12 which happens to be right beside CN04. Any blackened traces or other signs of corrosion around those connectors?
Don Backshall

Re: [PolySix] Re: Dead Keys are Stuck in Arp

2018-04-20 by Florian Anwander

Hello

Dons analysis is excellent. After your description of pressing the panel buttons, I'd say the cause for the stuck note/dead keys problem is a corrupted/broken diode either on the panelboard or the keyboard. If you look at the service manual page 7 (new board) or page 5 (old board), you will see, that the bus P10-P17 is shared between the keyboard matrix and the panel board KLM371, but the panel switches are returned to a different bus than the keyboard. If a diode in this matrix is letting currents pass in the wrong direction unpredictable things may happen.

If you had a battery leaking, then a diode might suffer from it. I had it several times, that the glass body of diodes got leaking, because the metal of the wire corroded, so a gap between the wire and the glass appeared and humid air could reach the inner of the diode, which again causes the diodematerial to change its characteristics.

Unfortunately the service manual doe not contain a schematic of the keyboard, so we cant tell which port line this is.

Florian


On 20.04.18 03:33 , jhatzia@gmail.com [PolySix] wrote:
 

Thank you Don- you really nailed describing my situation. I'm working on it again now. And was trying to reply to your comment to get a new description on the hanging note but it started working again..?

After leaving the synth on for a while I couldn't even get Chord Mem or Hold buttons to react. After cycling the power they reacted again but had hanging notes.. I was then pressing all the key assign buttons and after some clicks it started behaving properly... Now all those dead notes are playing fine (except the last G, A & A# are still very dead).. Very odd. I wouldn't be surprised if it happens again. I'm still unsure where a fault like that would be found in the circuit.

Well- I still have to install about 3 new button cap holders and clean the volume pot, so I would be surprised if the issue arises again, if it does I'll make sure to update this thread.




Re: [PolySix] Re: Dead Keys are Stuck in Arp

2018-04-20 by <backshall1@bellsouth.net>

With the speed at which my messages are appearing, Yahoo must be using a satellite relay somewhere outside the orbit of the moon. Either that or we are 670,616,629 miles apart.
For the panel board, there is a slight possibility that something is physically being shorted out when the machine screws are tightened. The M3 screws that hold this board are supposed to have a plastic washer on them. Are the washers all there? More likely, there is some sort of cracked solder joint or trace that gets disconnected when the board is flexed. This board can get warped and sag quite a lot, particularly around the 1-8 buttons. I’ve heard this is due to heat from the transformer over the years.
I have seen several keyboard contact boards with bad diodes and/or blackened traces. I assume it’s from several acidic carbonated beverages spilled on the keys over the years. You can’t just wipe off the keys when that happens. The real damage is underneath.
Don Backshall
 
Sent: Friday, April 20, 2018 3:38 AM
Subject: Re: [PolySix] Re: Dead Keys are Stuck in Arp
 
 

Hello

Dons analysis is excellent. After your description of pressing the panel buttons, I'd say the cause for the stuck note/dead keys problem is a corrupted/broken diode either on the panelboard or the keyboard. If you look at the service manual page 7 (new board) or page 5 (old board), you will see, that the bus P10-P17 is shared between the keyboard matrix and the panel board KLM371, but the panel switches are returned to a different bus than the keyboard. If a diode in this matrix is letting currents pass in the wrong direction unpredictable things may happen.

If you had a battery leaking, then a diode might suffer from it. I had it several times, that the glass body of diodes got leaking, because the metal of the wire corroded, so a gap between the wire and the glass appeared and humid air could reach the inner of the diode, which again causes the diodematerial to change its characteristics.

Unfortunately the service manual doe not contain a schematic of the keyboard, so we cant tell which port line this is.

Florian


On 20.04.18 03:33 , jhatzia@gmail.com [PolySix] wrote:

 

Thank you Don- you really nailed describing my situation. I'm working on it again now. And was trying to reply to your comment to get a new description on the hanging note but it started working again..?

After leaving the synth on for a while I couldn't even get Chord Mem or Hold buttons to react. After cycling the power they reacted again but had hanging notes.. I was then pressing all the key assign buttons and after some clicks it started behaving properly... Now all those dead notes are playing fine (except the last G, A & A# are still very dead).. Very odd. I wouldn't be surprised if it happens again. I'm still unsure where a fault like that would be found in the circuit.

Well- I still have to install about 3 new button cap holders and clean the volume pot, so I would be surprised if the issue arises again, if it does I'll make sure to update this thread.

 
 

Re: Dead Keys are Stuck in Arp

2018-04-20 by jhatzia@gmail.com

Thank you everyone for all the input. I will be addressing the dead keys that have no relation to the stuck notes in the arp last.

The screws are missing washers underneath the panel board. I was thinking Im going to screw it in tight to recreate the problem and then check all the traces for continuity. I'm thinking the pressure is causing a trace to disconnect and is causing this issue. Still very odd to me that it would affect keys not working/getting stuck in the arp.

Re: Dead Keys are Stuck in Arp

2018-06-06 by jhatzia@gmail.com

So I think I've found the issue. There is a hairline crack right underneath ARPEGGO SW4 in this picture.
https://www.dropbox.com/s/avkgfs2md4us07f/IMG_6570.JPG?dl=0

I was going to replace all the switches in the board and noticed this. I'll test continuity and try and jump any missed connections. Does anyone have any other suggestions how to tackle this?

Sorry I'm posting from my other account.

-cufflynxinc (jhatzia)

Re: [PolySix] Re: Dead Keys are Stuck in Arp

2018-06-06 by Bob Grieb

Don't use only solder to bridge the traces across the crack.
Scrape off the solder mask on either side for maybe 1/4" or more
and lay a piece of resistor lead or something similar across the
crack then solder to the trace on both sides. In really severe cases,
you could glue something flat like a piece of some old pc board
to this one to span the crack in-between where the traces are to make
it stronger. In most cases just fixing the traces is enough.

Re: [PolySix] Re: Dead Keys are Stuck in Arp

2018-06-06 by Peter Foley

Is there any advantage to attempting to fix the traces over using a jumper?

On Jun 6, 2018, at 08:34, Bob Grieb bobgrieb@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:

 

Don't use only solder to bridge the traces across the crack.
Scrape off the solder mask on either side for maybe 1/4" or more
and lay a piece of resistor lead or something similar across the
crack then solder to the trace on both sides. In really severe cases,
you could glue something flat like a piece of some old pc board
to this one to span the crack in-between where the traces are to make
it stronger. In most cases just fixing the traces is enough.

Re: [PolySix] Re: Dead Keys are Stuck in Arp

2018-06-06 by <backshall1@bellsouth.net>

Just solder alone over a broken trace is not sturdy or stable. Follow Bob’s suggestion and lay a piece of bare wire over the break and solder it on.
Don B
 
Sent: Wednesday, June 6, 2018 8:55 AM
Subject: Re: [PolySix] Re: Dead Keys are Stuck in Arp
 
 

Is there any advantage to attempting to fix the traces over using a jumper?

On Jun 6, 2018, at 08:34, Bob Grieb bobgrieb@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:

 

Don't use only solder to bridge the traces across the crack.
Scrape off the solder mask on either side for maybe 1/4" or more
and lay a piece of resistor lead or something similar across the
crack then solder to the trace on both sides. In really severe cases,
you could glue something flat like a piece of some old pc board
to this one to span the crack in-between where the traces are to make
it stronger. In most cases just fixing the traces is enough.