Milwaukee made lo duca bros (midget) the A major button leaves valve open slightly on some key(s) after compression

[radcordion]

I tried checking for any obvious issues, the button does not stick, or rub, and no pins appeared as obviously out of place or stuck either, when i push down the appropriate pins move, and appear to return to posiion after. It used to happen ocassionally, and started happening with increasing frequency till i smash about on the buttons a while and then it will release. Any suggestions of what the issue might be or how to locate the source of the trouble?

 

[JerryPH]

I am going to assume you mean the chord button on the left hand? Pressing the A button on the right and having it open different notes *would* be weird… lol

You probably just need a service on the bass mechanism if it’s dusty/dirty and sticking.

 

[radcordion]

yes the A MAJOR button on the left hand, its not espescially dusty or dirty, im having a hard time finding anything sticking, everythign appears to slide back, obviously something is not returning correctly, hence the post if anyone has specific suggestons of how to troubleshoot to pinpoint the source itd be apperciated. I've tried going up and down each column with my eyes and an extra light, but nothing stands out as the culprit.

 

[boxplayer4000]

You probably just need a service on the bass mechanism if it’s dusty/dirty and sticking.

radcordion: The fault you describe is probably the most common with bass mechanisms. A careful clean and a check of the button and piston alignment will probably reveal/cure the fault.

 

[radcordion]

radcordion: The fault you describe is probably the most common with bass mechanisms. A careful clean and a check of the button and piston alignment will probably reveal/cure the fault.

Thats usually how I fix the problem, and was the first thing I tried, but this time the button returns to its position even though the valve stays open, and I cant find any point where its sticking. im looking for recommendations or resources of how to find the problem when the problem evades the obvious.

 

[debra]

The A major button may return completely because it is pushed up by the C# and E in the chord. You should check whether none of the (many) pistons that play the A note is pushing down on the A catorcetto (lever) a bit.

 

[Ventura]

left field..

the spring that pushes the button back up gets it's return energy
from pushing the button down

the spring that pushes the pallet back down on the hole i think
might be a separate spring in some types of bass actions

just because the button returns correctly does not
insure that the pallet re-seats correctly

the pallet could also have a loose leather that (now) has a folded
corner occasionally drooping in the way

 

[debra]

...
the spring that pushes the pallet back down on the hole i think
might be a separate spring in some types of bass actions

just because the button returns correctly does not
insure that the pallet re-seats correctly
...

That is right, and these are actually two separate issues.
The button returning is a consequence the three notes of the chord "pushing it back". But in reality only one note is needed to push the button back. It doesn't matter whether one two or all three pallets close. One of the three catorcetti is enough to push the button back up.
The second issue is that the bass mechanism (in a non-convertor accordion) contains separate springs to help push back the catorcetti.
I didn't have a picture ready but I found this video. On the left side of the video you see a U-shape bracket with two strips of felt. This is pushed back by a spring mechanism and it pushes all 12 catorcetti back. Alternatively the bass mechanism on other accordions has a fixed bracket and twelve small springs pulling the catorcetto towards the bracket. So you see: the catorcetti are pulled/pushed back by a mechanism that is independent of what the pallets are doing.

 

[dak]

That is right, and these are actually two separate issues.
The button returning is a consequence the three notes of the chord "pushing it back". But in reality only one note is needed to push the button back. It doesn't matter whether one two or all three pallets close. One of the three catorcetti is enough to push the button back up.
The second issue is that the bass mechanism (in a non-convertor accordion) contains separate springs to help push back the catorcetti.
I didn't have a picture ready but I found this video. On the left side of the video you see a U-shape bracket with two strips of felt. This is pushed back by a spring mechanism and it pushes all 12 catorcetti back. Alternatively the bass mechanism on other accordions has a fixed bracket and twelve small springs pulling the catorcetto towards the bracket. So you see: the catorcetti are pulled/pushed back by a mechanism that is independent of what the pallets are doing.

You also see a microphone installation. Here is the deal in my opinion: the only instrument of mine where I've seen that U-shape bracket is an Excelsior with factory MIDI installation. The purpose of the U-shape bracket is to make sure that if
a) bass buttons are being pressed
b) chord pallets get opened along with the bass pallets because of the bass/chord note coupling mechanism
c) no chord buttons are being pressed
then the chord catorcetti(?) are being held back together in the "unpressed" state by a single spring to keep chord MIDI notes from sounding randomly by catorcetti moving of their own accord when constrained neither by a pressed chord button nor by the spring of a closed chord pallet.

Since all the chord catorcetti are held back by a single spring, there isn't much additional resistance to overcome. The problem is that if you press, say, C bass together with Em chord, then the C chord catorcetto again is unconstrained and may move at its discretion, adding a C chord note to the MIDI at a random point of time.

So because this is the only context where I've seen this construct in my own instruments, I think it may be a crutch for MIDIfication of standard bass accordions that couple bass reeds into chord reeds (almost all of them do).

A corollary will be: if pressing down C, E, G bass buttons, will the C Major chord button fall in? With this construct the answer is no, without it the answer is yes. But I don't think this is the motivation because, well, who cares as long as no MIDI comes into play?

 

[debra]

You also see a microphone installation. Here is the deal in my opinion: the only instrument of mine where I've seen that U-shape bracket is an Excelsior with factory MIDI installation. The purpose of the U-shape bracket is to make sure that if
a) bass buttons are being pressed
b) chord pallets get opened along with the bass pallets because of the bass/chord note coupling mechanism
c) no chord buttons are being pressed
then the chord catorcetti(?) are being held back together in the "unpressed" state by a single spring to keep chord MIDI notes from sounding randomly by catorcetti moving of their own accord when constrained neither by a pressed chord button nor by the spring of a closed chord pallet.

Since all the chord catorcetti are held back by a single spring, there isn't much additional resistance to overcome. The problem is that if you press, say, C bass together with Em chord, then the C chord catorcetto again is unconstrained and may move at its discretion, adding a C chord note to the MIDI at a random point of time.

So because this is the only context where I've seen this construct in my own instruments, I think it may be a crutch for MIDIfication of standard bass accordions that couple bass reeds into chord reeds (almost all of them do).

A corollary will be: if pressing down C, E, G bass buttons, will the C Major chord button fall in? With this construct the answer is no, without it the answer is yes. But I don't think this is the motivation because, well, who cares as long as no MIDI comes into play?

I have not yet had the "pleasure" to work on any accordion with midi installed (and knowing who I play with, what we play, and that those are the only people I do repairs for) and I have seen one of the two methods to hold the chord catorcetti back (the method with one spring shown in the video and the method with one spring per catorcetto) in many recent (<30 years) accordions. I doubt the very cost-conscious accordion manufacturers would go to the expense of installing the bracket and spring mechanism in all accordions, just to serve the maybe less than 5% that are also equipped with midi.

 

[debra]

Just opened up the bass compartment of a Scandalli Super VI LX to show what's inside.

 

[jollyrogeraccordions]

Unfortunately a pallet staying ever so slightly open can be for any number of reasons. Recently (and incredibly) the same problem caused this symptom on two different accordions…which was…the spring was dislodged from the top of the pallet..so it was still pushing the pallet back, but with reduced force. Only fixed by removing pretty much all of the bass machine. Which isn't a big deal if like me you've done it lots of times (it takes about 1:30 to get it out and then back).
For diagnosis of this kind of problem I get the bellows off and the reed blocks out and inspect from that side. You can see if there is an issue with the pallet facing…you might get lucky and be able to fix the issue from that side if there is some debris in there. I have even refixed a pallet facing with tweazers from this side as well.
I'm talking about a regular Italian style bass machine that comes apart easily. Some machines come out in cassette style pieces (e.g, Hohner and some Chinese made PAs), which makes life a lot easier).

 

[radcordion]

Thanks for the suggestions and video debra, ventura, I am going to give it another go, Ill update when i find the source

 

[colinm]

Radcordion, did you solve this, following some rough handling i have f sharp sounding continuously in the bass ?