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Hi, is there anyone kind enough to explain for me why all white key backchecks are in a line, and all the black ones are in another line. You can see the pattern of two and three black key groups, and white white also. The black key backchecks are more away from the tail.
The checking is also affected the same way, the black keys, when lifted by hand to the same height and dropped, while holding thge key depressed, are checking lower.
Is this normal? Shouldn´t all backchecks be in perfect alignment and all hammers check at the same level at same force/height?
Thanks.

I would check the keydip.

Ah, I see. So it should be in line.
I looked at the end of keys, they are at same level when not depressed. But probably that means that it's at the front that height is wrong, and only the blacks, as white have 10 mm. It's harder to measure the black ones, but I'll try. If it's 9+, or 11-, that's the problem, or?
Thanks for the tip.
Just to be sure, they should check at same level, and should look perfectly aligned when not played, right?

No, the dip is not the problem, but the height of the black keys on the balance rail could. I suppose someone put new shims on the pins of the black keys only, and elevated the keys at the middle very little, but enough to have this effect. Don't get why the dip seems ok. Back to the piano.

I suspect someone was trying to increase the dip by adding balance rail punchings for the black keys. With regulation, unless you get to the root cause of the issue and you cure only the symptom, you get into trouble in another area.

Don't bend the backcheck wires yet. Get the key height and dip squared away--not to mention the other aspects of regulation that should come beforehand--before you regulate the checks.

Yes, that's it. I didn't bend, as I felt also it's not the answer. This is a Hamburg O, from 29, very good condition, normal wear, not battered. I measured the dip, but without gigs and gauges it's not easy to be precise. I think I found it's over 10mm, like 10,4 or so. I think I know what to do. The other parameters are regulated, but only in second section, as I work there until it's done, it's also a region I can test by actually playing.
One other thing, as the action was too light for my taste, I took out the support springs from the end of the whippen, only out of the thread loop. Feels great, huge improvement. It's a bit noisy now, but I will take them out totally next time I regulate. Cause I have to take the whippens out, and I don't want to go thru that again, for a while. Would you consider a crime taking those springs out? I think it's not just putting them back, as the felt comes out. I don't see the meaning of these springs, why make the action light, it's uncontrolable. Maybe when everything is new, hammers not filed and so on...

Oh, I know I have to do the strike distance, let off, drop, if I do anything with the dip.

You should be able to easily measure key dip with a simple 10cm steel rule to within <0.5mm and that is accurate enough for now.
You should take the time to evaluate the touchweight before removing the whippen helper springs or put them back on and see what you have. Possibly they only need weakening. Their purpose is to remove some or all of the weight of the whippen from the key - they reduce key down and upweight.
Changing key dip should only effect aftertouch.

I have written a very long post, and I will post it after this warning. Please don't read that next post if you'll get annoyed, it's very detailed, and maybe confusing. Asks too much of you really, so here is the supershort version.

Should the keys, the actual surface of the wood, at the balance rail, have absolutely the same height, whether black or white?
Cause on my piano it isn't. Black keys sit lower on pin.

This causes some strange stuff to happen, explained in next post, only for people that have spare time, and a very forgiving nature :-)

Thanks Gene,
About springs, they are still there, easy to hook and unhook, so I'm going to do exactly what you said, thou the way it is now it feels the right touch.

My big problem is that I am not sure if the height is wrong at the balance rail, or in front of the keys, as I have two sets of *data*, one for white keys, one for black keys. It's hard to explain with words, but I'll try:
I took out the action rack . Now I press all keys down fully, at the back where the felt strip that lifts the dampers is, forcing the front of keys to go up. Now I see all the back checks forming the pattern of -white black white black white white- where the corresponding back check of a white key is leaning less than the black ones, or the black ones are more laid back, so to speak. But looking at the line formed at the top, it looks as all checks have the same height, or length, they are equally tall. Sorry for over explaining, just to be sure I give the real picture.
Now I press the keys in front, as I would play them, I don't really need to press, they want to go down, but I make sure it's all of them and the same pressure, and now I get backchecks perfectly aligned as leaning goes, but the height gives me the white black key pattern, were the black are taller. If I look at the end of keys, where the red strip of felt is, all keys have two different heights, making the wbwbww pattern. And the difference between the position of black vs white is over 1 mm.
Also, when all keys depressed, if you look at the wood, where the ivory ends, the white keys sit higher than black, and at the balance rail pin is also obvious they are higher. I took out for one white key, all shims and punches, doesn't affect this, still higher att balance rail.

Now, is this normal? Who would bend all back checks to have two positions when keys at rest? And back checks aligned when keys depressed fully. But different levels at the end of the keys. I looked at damper levers inside, and they sit at same level, so they get lifted differently when key fully depressed.

what I don't know is:
1. should all backchecks have same position in diff pos of keys, and look as a straight line both in rest pos or depress pos, check exactly in the same way both for black and for white, and the keys at the back should have same height when depressed or at rest, and all keys should have same height at balance rail?
Then I have to take out shims from black keys at balance rail, or put more from white. And then work with the front to get right dip.
Or

2. They should be the way they are, keys at back make a pattern while depressed at front, having two dif heights for black vs white.
In this case, the same question, should all backchecks check the same? Should look in line when keys depressed, thou make the pattern when in rest pos? Than I have to bend them for getting them do same job.

I think that the first one is the right one, but I need to know from you before I start working. Thanks.

Have the white keys been re-surfaced? On one of my pianos, this was the case. I presume the new plastic key-tops were thicker than the original ivories, and instead of taking some wood off the white keys before gluing on the new key-tops, the rebuilder simply glued them onto the original keys. Now, the white key-tops were too high, and in order to prevent the black keys from disappearing between the whites when fully depressed, the rebuilder then lifted all the black keys by putting extra shims on to the balance rail pins. This, of course, increased the key dip on the black keys...

1: As you are looking at the other end of the key in detail I will say that they all may move very slightly different - as the length of the keys usually tapers from bass to treble, the sharps are shorter than the naturals, and front, balance and back rails may or may not be paralell to eachother - all keys have slightly different ratios and symmetery back there is lacking. The question is - how do you want the key ends to move and I like the key end felts to be all at the same height when the keys are fully dipped. Making this happen is another story. These decisions get into damper regulation as well as checking.

2: I like to judge checking by observing the hammers while in check. Are they all checking efficiently at the same distance from the string?

Beyond this your action may need regulation starting with setting key height and working through the steps. It is difficult to know what you are dealing with from here.

Very basic concept even for a nontech,you add punchings on the sharps as in raising them at the balance rail,the backchecks lean further back.

Thanks for taking the time to write and help. I am learning more and more. This one thou has the original ivories, and they are quite thin. I went to a church yesterday, and there was a Yamaha C3 there. as it was no one around, I took out the fallboard, and saw that it had the same difference between the white and black, at the level of wood. So I left the balance rail and front alone, and just put the hammer strike distance at 44,5, with a rig I made with pieces of wood from a bookcase. Then let-off, drop, jack that needed to go more towards hammers, and backchecks. For backchecks, I corrected some that went in too low, and others that would escape directly, couldn't be kept down. I just scratched easily on hammer tail, to increase friction, and went over the leather with my nail. It worked. All this because nothing is really wrong with the piano. The wear makes it less than perfect, but it's better than all the pianos I practiced on when in conservatory. So, now I'm saving for my D. It will come.

Yes, you put the finger on it, it's difficult to get the same dip, and same behavior at the back, with different lengths of the keys. So, as I am not a tech, I decided to leave it the way the last person who worked on it put it, which is, correct dip in front, slightly higher black keys on the balance rail, and at the back, the line is not straight at dip, the black keys go a little bit further, maybe 0,5mm. But the checks are straight on dip, and it checks correctly. I learned quite a lot in these 4 months, so now I can go on one note that gives me trouble and see what's wrong.
Great feeling when everything is done, but my hands hurt from all regulating, especially in the morning.
Thanks everybody.