Author Topic: CP70 Double Stroke Issues  (Read 359 times)

Offline GabGarfield

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CP70 Double Stroke Issues
« on: April 03, 2020, 05:02:55 PM »
Hey guys,

I'm new here but I'm already loving this community, so maybe you can help me out.

My CP70 is starting to have a little issue with the action on some notes, so everytime I press a key medium hard I get a little double stroke on the tone. It seems like the hammer is bouncing back, but I don't know where exactly in the key action the issue could be. Does anybody with a CP70 know this issue and what part of the key action is responsible for that?

best Regards,

Offline OZDOC

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Re: CP70 Double Stroke Issues
« Reply #1 on: April 03, 2020, 09:32:36 PM »
There are some actual piano tuners on this list who may chip in with more useful information.
My understanding is that this will be to do with the action back check.
Here's a video talking about it.
But your issue may not be an adjustment issue, it may be a materials wear issue. For example felts may have worn too smooth.
Look closely at the action of two adjacent notes in your piano - one that is checking properly and one that is bouncing - to see if you can see obvious differences in the setup distances, back check angle, and wear of things like the felt surfaces.
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Offline pianotuner steveo

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Re: CP70 Double Stroke Issues
« Reply #2 on: April 04, 2020, 08:27:57 AM »
Never bend/ adjust a backcheck in a piano action until you are 100% sure that is the actual issue. (Btw, the angle in most pianos is around 60-65 degrees) Someone prior to you may have bent the back check too far away, so compare it to its neighbors, like David said.

I could not hear audio on the video link, so
I'm not sure if any of this was mentioned or not...

The first 2 easy things to check are key dip and Letoff. Letoff could be letting off just a tad late, and/or the key dip may be slightly shallow. If the key is pressing down exactly the same amount as it's neighbors, then try turning the Letoff adjustment so that the button contacts the jack heel slightly sooner. If the dip is too shallow, try removing one paper/cardboard punching under the green felt punching at the front of the key.

If this is only happening on one key, I doubt it is a wear issue.

It could also be an adjustment for the repetition lever. The Jack may be too high "in the window"
A local piano tech will know what that means.

Does the key work better when hit hard? If so, that may indicate Letoff. The key dip could still be a little shallow too.
« Last Edit: May 24, 2020, 05:16:21 AM by pianotuner steveo »
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