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Kronos 88 multiple keys above Middle C suddenly not working
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AntonySharmman
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Joined: 16 Oct 2010
Posts: 2448
Location: Hellas

PostPosted: Mon Aug 07, 2017 10:48 pm    Post subject: Reply with quote

I don't really know what are the criteria that somebody could believe that there is even a case in the million ,
that copper strips of board could have been discontinued when picoAmperes are circulating there ... only by
shooting keyboard with a gun this could have happened , or the whole production line of Kronos PCB would
be faulty in engraving procedure !
PCB short connectors wire cables stracture is crystal clear that could never create a discontinued current flow issue ,
so only master connector could be suspicious and only under physical force/pressure circumstances as I've already explained ,
and the next step is the maintance of carbon contact strips , where the same symptoms can be occurred !
Next level hardware issues like controller ICs definitely needs authorized service !
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gilianamsterdam



Joined: 08 Jul 2017
Posts: 10

PostPosted: Mon Feb 12, 2018 10:37 pm    Post subject: Reply with quote

Hi,

It took me a while to respond in between a lot of touring and projects. I wanted to report that:

- When I carefully examined the MKB1 board, it turned out to have some kind of black spot on the copper strips, presumable from moist buildup in the Kronos. This is where it must have shorted out.

- I ordered the MKB1 part anew from Korg and received a MKB2 with it.

- I installed both new boards in the Kronos, and carefully reconnected the connectors.

- After booting, keys F6, G#6, C7, E7, G#7 and C8 are not working. I have unable to fix this. If I switch the new MKB2 back for the old one, it still doesn't work.

Does anybody have any thoughts on this?

Many thanks,

Gilian
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alland
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Joined: 17 Jun 2009
Posts: 490
Location: Estonia

PostPosted: Tue Feb 13, 2018 5:54 pm    Post subject: Reply with quote

1) MKB1 and MKB2 - are these PCBs under keys? And is MKB1 on lower keys side and MKB2 upper keys side? Just to get context, because my schematics does not describe them so.
2) Keys G#6, C7, E7, G#7 and C8 not playing makes sense according the schematics, but not together with F6 but with E6 (and perhaps also with C6, G#5, E5, C5, G#4 and E4). But you are sure that exactly F6, G#6, C7, E7, G#7 and C8 not playing?
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gilianamsterdam



Joined: 08 Jul 2017
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PostPosted: Sat Feb 17, 2018 1:57 pm    Post subject: Reply with quote

alland wrote:
1) MKB1 and MKB2 - are these PCBs under keys? And is MKB1 on lower keys side and MKB2 upper keys side? Just to get context, because my schematics does not describe them so.
2) Keys G#6, C7, E7, G#7 and C8 not playing makes sense according the schematics, but not together with F6 but with E6 (and perhaps also with C6, G#5, E5, C5, G#4 and E4). But you are sure that exactly F6, G#6, C7, E7, G#7 and C8 not playing?


Hi alland,

Thanks for your answer.

I uploaded some pictures illustrating the parts replaced and what keys are not working, it might be I got the key names wrong.

I've examined the "bridge" between the two parts as well as all other connectors and everything seems connected properly.

When you say that a certain combination of keys could make sense is that because they share a pin on the connector? Which connector is that? I could then recheck.

Is it possible the blue rubber keybed beneath it causing the issue?

Thanks again for your help so far!

Gilian
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alland
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Joined: 17 Jun 2009
Posts: 490
Location: Estonia

PostPosted: Sat Feb 17, 2018 3:37 pm    Post subject: Reply with quote

I did not find your pictures.

You can see from that piece of schematics why some keys not working together makes sense.
https://photos.app.goo.gl/ZYxpLuJKOFmFWiNi1
Key scanning works like this:
Controller sends binary code (up to 32 combinations) using five bit bus SS0..SS4. This 5-bit signal is decoded by three decoder chips into three buses YA00..YA07, YB00..YB07 and YC00..YC05 and then controller reads key state from bus T00..T07.
There is also connectors between two PCBc and if scanning by the same lines works on one PCB and not on other, then most probably something is wrong with connectors.
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gilianamsterdam



Joined: 08 Jul 2017
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PostPosted: Sat Feb 17, 2018 4:47 pm    Post subject: Reply with quote

[quote="alland"]I did not find your pictures.

Apologies I forgot to add the link Smile

https://imgur.com/a/kOzM1
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alland
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Joined: 17 Jun 2009
Posts: 490
Location: Estonia

PostPosted: Sat Feb 17, 2018 5:22 pm    Post subject: Reply with quote

Thanks for photos.
I posted picture of Excel when you can see affected keys and which signals are involved. Key F6 still does not fit to pattern, but who knows...
https://photos.app.goo.gl/q2GYO9gH8XnCPcfw2
I'd just take out PCB for upper part and do close inspection of printed wires and connections that come from affected keys to see something unusual (broken, shorted etc).
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