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 Forum index » DIY Hardware and Software » The Repair Shop
Strange keyboard behaviour. (Solved)
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muzmuz



Joined: Feb 11, 2018
Posts: 4
Location: Tasmania

PostPosted: Thu Feb 22, 2018 8:50 pm    Post subject: Strange keyboard behaviour. (Solved)
Subject description: Roland VK1000
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Hi all,

I have a weird issue with a Roland Rhodes VK1000 keyboard… Hopefully someone has had a similar issue and might know how to solve it!

What’s happening is the keyboard is acting as if it has been split into groups of 16 notes. Each group of 16 are correct within themselves, however, the 16 next to it start at the wrong place. Described another way - if I play the keyboard chromatically from low to high, the first 16 notes are fine, but then the keyboard jumps back a few tones and plays 16 notes, then it jumps up a few notes and plays 16 again.
Also, one group of 16 has no touch sensitivity. To top it off, if I play any one of the top three notes, the keyboard plays a group of low notes and they hang. The only way to stop them is to power off the machine.

I have done a fair bit of troubleshooting with no result. I see that the chip controlling the keyed (R15239124) is a common one shared with other roland keyboards such as the D5, A30, E16, and I guess others as well.

A couple of other things… MIDI in responds as it should - I can control the VK1000 with a MIDI controller properly. MIDI out reflects the strange behaviour. Factory reset (called cold boot) has been done with no effect on the issue.

Has anyone seen this issue before? Maybe someone could help shed some light for us? Thanks heaps for reading!

Muz.

Last edited by muzmuz on Tue Mar 20, 2018 4:39 pm; edited 1 time in total
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DES



Joined: Feb 28, 2003
Posts: 783
Location: New Jersey
Audio files: 8

PostPosted: Fri Mar 09, 2018 11:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

Have you disassembled the keybed and inspected it for corrosion, foreign objects (I had an old Farfisa come into the shop that had about a dozen paper clips in the keybed...) bad connections...? I'm not familier with that instrument but in my experience most problems with the keybed were due to beverages being spilled into them, foreign obects and diodes. Obviously more can and does go wrong, but most of what I've seen fell into the above catagories. The diodes are not as common as they used to be because of the scanning chips used now...look closely at pins around ic's and make sure they're clean. The diodes were likr 1n4148, 1n914...general purpose diodes easily tested with a multimeter....

Oh - also look for capacitors that may be failing though that would most likely cause different issues like a totally dead keyboard, etc...

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muzmuz



Joined: Feb 11, 2018
Posts: 4
Location: Tasmania

PostPosted: Mon Mar 12, 2018 3:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Des,

Many thanks for your reply. I've gone ahead and checked all the diodes and they were all reading very close to each other at 0.65V. They keybed and contacts were actually pretty clean, but I cleaned up the little dots with deoxit anyway. I have checked the voltages and they're good - I haven't replaced the caps as I was measuring very little AC in the 5V that runs that area.

An interesting thing is that there are three ribbon connectors for the keybed - and each one sends a signal for a section of the keyboard. As I unplug each one, the corresponding section of the keyboard signal is lost, BUT the strange behaviour remains! So I have called Roland and ordered a replacement scanning chip - the SSC1000 or R15239124. It's on its way now. After it and the SMD desolder kit I ordered arrive I'll swap it out and see what happens. Here's hoping it fixes it.

Muz.

DES wrote:
Have you disassembled the keybed and inspected it for corrosion, foreign objects (I had an old Farfisa come into the shop that had about a dozen paper clips in the keybed...) bad connections...? I'm not familier with that instrument but in my experience most problems with the keybed were due to beverages being spilled into them, foreign obects and diodes. Obviously more can and does go wrong, but most of what I've seen fell into the above catagories. The diodes are not as common as they used to be because of the scanning chips used now...look closely at pins around ic's and make sure they're clean. The diodes were likr 1n4148, 1n914...general purpose diodes easily tested with a multimeter....

Oh - also look for capacitors that may be failing though that would most likely cause different issues like a totally dead keyboard, etc...
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muzmuz



Joined: Feb 11, 2018
Posts: 4
Location: Tasmania

PostPosted: Tue Mar 20, 2018 4:38 pm    Post subject: Solved! Reply with quote  Mark this post and the followings unread

Just posting here for anyone who might have this or similar issue in the future. The fault was in the R15239124 chip. I replaced it (a bit of a challenge as it's got heaps of pins and is surface mount) and the keyboard works as it should now.

Rock n roll!
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electrojoe



Joined: Apr 04, 2018
Posts: 1
Location: Minneapolis MN

PostPosted: Wed Apr 04, 2018 3:54 pm    Post subject: Rolland Part Reply with quote  Mark this post and the followings unread

Hello,
I have a JD 800 that has the same issue.
How did you order the part from Roland, now that they won't sell to small repair business's?

Please let me know, as the repair shops in my area are not helpful.

Thanks.

Electrojoe
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muzmuz



Joined: Feb 11, 2018
Posts: 4
Location: Tasmania

PostPosted: Wed Apr 04, 2018 5:10 pm    Post subject: Re: Rolland Part Reply with quote  Mark this post and the followings unread

Joe, I'm not aware of Roland not selling to certain people. I'm a long way away from you tho. I called Roland Australia and the fellow found one for me. It wasn't cheap ($50). Others here might be able to guide you in your case or call Roland Australia I guess.

Muz.

electrojoe wrote:
Hello,
I have a JD 800 that has the same issue.
How did you order the part from Roland, now that they won't sell to small repair business's?

Please let me know, as the repair shops in my area are not helpful.

Thanks.

Electrojoe
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