How Do I Fix My Bass Machine?

[hoag]

Howdy!

I have lurked on these forums for a while, and this is my first post. Shout outs to the people who approved my account activation.
I'm restoring a Hohner Tango III M, which was made in Germany. I was told that it was built and bought in the 1930's, but I have not researched this yet. It had many issues upon purchase, many of which I have resolved. It still has a few problems that require attention. I am a veteran luthier, and novice accordion repairman. My current project is the bass machine, and it is just a bit beyond my understanding. This is where I'm hoping you all come in!

Many of the bass buttons were depressed within the machine, when in a resting state. I'm not exactly sure what that meant. The machine also had some jumped pins, which I was able to confidently diagnose. It was the G dominant piston, and the Eb major piston. They were constantly sounding when opening and closing. After locating which pistons were out of place, I decided to disassemble the mechanism for a de-rusting and deep cleaning, using the guidance found throughout these forums. It desperately seems to need the old steel wool treatment. I was also able to confirm that the bass side pallets were not the culprit, after removing the bass machine. They all need a refacing, but my paper solution works until I receive my order from Carini. All is going smoothly, and I have disassembled most of the bass machine. I still have the combs and their structural brackets left to disassemble, but that is a job for daylight.

(TLDR) Here are my questions. How can I understand which piston nubs correspond with which comb teeth as I reassemble the bass machine? How do I know which piston nubs to place above or below which comb teeth? Can anybody offer a resource detailing the design for this specific model? How do I make sure that my combs spring back to their proper positions, as they should?

This is my first bass machine disassembly, please be gentle. I know now that I should have taken a photograph of each row before removing it. I've been taking photos of everything except for this critically important detail. I thought I was doing everything well until halfway through, when the thought hit me. "I know where everything goes, except where the nubs sit. Oh shit."

Thanks in advance.

 

[debra]

If you kept the pistons all in the right order then you already know which piston goes where. And as they are all bent you can easily see which way they go (so you don't put them backwards). As for each nub sits regarding which catorcetto (comb) that is also fairly easy: when a nub can move a catorcetto it should sit "above" the catorcetto's "tooth" so that when you press the button it moves the catorcetto. The buttons that were depressed within the machine were a result of the "jumped pin" problem: the nub on the piston has jumped past the "tooth" (lever) of the catorcetto it was supposed to push. A nub that's under the catorcetto cannot do anything so it's always wrong.
The main problem you are facing is that because the mechanism is removed from the accordion the catorcetti (combs) are not being pushed into their correct "resting position". So you have to first do that pushing yourself and then you have them in the right starting position for putting everything back together.
These Hohner bass machines were made specifically in this way so you hardly ever need to take them apart. You can take them out as two subassemblies and then you have easy access to everything without the need to take it further apart. (Obviously, too late now...) With Italian bass mechanisms you always need to take everything apart.

 

[hoag]

debra

Thank you kindly for your reply! Your posts are what have allowed me to safely disassemble my machine, and keep track of my bits and bobs. Your answer makes perfect sense, I was under the impression that some "nubs" should rest below some "teeth."

I aim to take just a bit of steel wool to each metal piece, including the catorcetti and their teeth. Then, I will take a soft tooth brush to dust away any small filings. Is this a proper way to go about de-rusting the beast?

I don't feel too ashamed by completely disassembling the thing, as it previously had some creatures living inside. I needed to ensure there are no insect eggs lodged within the mechanism, aside from the rust issue. I'm hoping that I'm along the right track, I'd love to have this box playing by the time power goes out here in Florida.

Here are some photos of my reassembly, thus far. I believe I have correctly placed my nubs onto the teeth of my catorcetti.

I tried installing just this part of my bass machine back into the bass side housing for a quick test, and I am faced with a similar issue as before. My buttons all stay down... Have I goofed somehow? I would expect this part of the mechanism to function properly without the chord assembly affixed. What should I do in order to test or ensure I have reassembled this mechanism properly? I believe that my pistons are in the proper spots, but none spring back up into playing position.

I wanted to get it reassembled with photos for more proper reference. I'm hoping that the extra images and information will prove helpful in diagnosing, and fixing, my problem.

As it will sit, the bass machine is installed inside of the housing. I believe I have placed my nubs properly, and reassembled everything correctly. I still have all of my buttons refusing to return to their respective playing positions. Is there something obvious I'm missing? I'm hoping this is a simple fix, due to my amateurish view of the mechanism. I'm really aiming to get this playable sometime tomorrow. Fingers are crossed!

Thanks to Dingo40 for pointing out the post editing function. Sorry, I'm still learning the ways here.
Thanks in advance! I could sure use a guiding eye.

 

[hoag]

Additional photos:

 

[Dingo40]

apologize for the triple posting,

As long as the post isn't the first of a new thread, you can very easily delete any further posts In that thread and alter or revamp them entirely to your complete satisfaction with the click of a button!
Similarly, although you can't totally delete a post starting a new thread, you can alter the contents, even the title, entirely to your own personal satisfaction.
Hence, reducing three inadvertent postings down to one should be a simple matter!

 

[debra]

The last four pictures show what I think is the mechanism in the correct fashion.the stubs are ready to push the levers of the catorcetti.
But in the pictures of the mechanism inside the accordion appears to be too far away ("up" in the pictures) from the levers that open the pallets ("down" in the pictures). The distance from the mechanism casing to these levers is too large, so when the pistons go down they go down all the way to touch the levers for the pallets but are not pushing them. Are you sure the mechanism is inside the accordion in the correct position?
But oh wait... There are two types of pistons! The pistons with the buttons have the stubs (nubs you call them) above the lever in order to push the lever down. But on each catorcetto there is one lever that pushes a piston down to open the pallet. That piston has no button. For this lever to push the piston down the stub needs to be under the lever because it is the lever that pushes and the stub is being pushed down. So on the pistons that come out of the mechanism at the bottom and that push the pallet open the stub must be under the lever.

 

[hoag]

The last four pictures show what I think is the mechanism in the correct fashion.the stubs are ready to push the levers of the catorcetti.
But in the pictures of the mechanism inside the accordion appears to be too far away ("up" in the pictures) from the levers that open the pallets ("down" in the pictures). The distance from the mechanism casing to these levers is too large, so when the pistons go down they go down all the way to touch the levers for the pallets but are not pushing them. Are you sure the mechanism is inside the accordion in the correct position?
But oh wait... There are two types of pistons! The pistons with the buttons have the stubs (nubs you call them) above the lever in order to push the lever down. But on each catorcetto there is one lever that pushes a piston down to open the pallet. That piston has no button. For this lever to push the piston down the stub needs to be under the lever because it is the lever that pushes and the stub is being pushed down. So on the pistons that come out of the mechanism at the bottom and that push the pallet open the stub must be under the lever.

Now that you point this out, again the lightbulb goes off! I'm ecstatic. This makes sense, as there are 24 levers, which should correspond to raising each of their respective 24 catorcetti. Fitting these underneath their proper stubs should correct my sea of sunken buttons.

I'll attempt to reconfigure this bass machine again after some sleep. I really appreciate the guidance, you've given me new hope!

 

[jollyrogeraccordions]

I've fixed many of these Hohner bass machines…they tend to jam …but I've always managed it without stripping them down completely. Well done.

 

[hoag]

I've fixed many of these Hohner bass machines…they tend to jam …but I've always managed it without stripping them down completely. Well done.

Thank ya kindly, it frustrated me quite a bit! I’m noticing that mine is a jammer. Have you learned any solutions to this?
I was considering installing some extra springs to strengthen the pallet levers, and thereby the return mechanism of the machine. I will need to be careful not to use too strong a spring if I try this…


Power is out here in the swamp, and will remain so for a few more days. I’ll attempt to update you all as I’m able.

The advice from debra, above, was on the money. I reorganized my levers, and the bass machine came back to life. It is finicky, and jams occasionally, with some buttons being particularly “unspringy.” I installed the machine back into my accordion, and now I’m left with my choice pallets leaking again.

I figure that it’s better to have an understanding of the bass machine, and have that problem solved. I can now confidently remove it in sections, or as a whole, to level and reface my bass side pallets.

Does anybody have advice for increasing tension in an old pallet arm spring/lever? A couple of mine refuse to push back up their respective button, even after setting the machine right.

Cheers, all! Thanks a million. I’ll be sure to update with photos and videos of the process and the sound as she comes together!

 

[pilagou]

I have nothing really useful to share except admiration. My other accordion is a Honner and I'm mightily impressed by someone being able to disassemble and reassemble that bass system. I had a look and concluded that nope... not for me

 

[debra]

Your bass mechanism shows that the pistons that push the levers for the pallets all have a double bend in them at the bottom. The end that pushes the lever for the pallet should be perfectly flat (some of yours are at an angle) and where the piston pushes the lever should be exactly under the long straight piston going up. Only then is the force of the pallet closing pushing the piston straight up. If the end is at an angle or not centered under the piston you get a force at an angle that pushes the piston towards the side of the slot it goes through and that causes resistance. (I recently fixed an Atlantic bass mechanism (they are all the same) where a few notes were sticky and the adjusting the lever to be centered under the piston, and making the end of the piston perfectly horizontal (versus the piston moving vertically) fixed the issue. No lubrication needed! No other bending or filing. Just making sure everything goes perfectly straight up and down.

 

[hoag]

Your bass mechanism shows that the pistons that push the levers for the pallets all have a double bend in them at the bottom. The end that pushes the lever for the pallet should be perfectly flat (some of yours are at an angle) and where the piston pushes the lever should be exactly under the long straight piston going up. Only then is the force of the pallet closing pushing the piston straight up. If the end is at an angle or not centered under the piston you get a force at an angle that pushes the piston towards the side of the slot it goes through and that causes resistance. (I recently fixed an Atlantic bass mechanism (they are all the same) where a few notes were sticky and the adjusting the lever to be centered under the piston, and making the end of the piston perfectly horizontal (versus the piston moving vertically) fixed the issue. No lubrication needed! No other bending or filing. Just making sure everything goes perfectly straight up and down.

I will follow your advice, you seem not to miss with this stuff!

That being said, I have my suspicions that increased strength will be needed even after straightening my levers. Once I straighten them out, I imagine the buttons will spring back better, and I imagine the pallets will have an even tougher time closing all the way. Could you offer a solution, should this prove true?

Separately, I was thinking of picking up some materials from my local Hobby Lobby for refacing the pallets. Any materials suggestions? Thickness recommendations?

Power just came back on, so I’m able to post and reply in a more timely manner. Thanks again, all!

 

[debra]

...
That being said, I have my suspicions that increased strength will be needed even after straightening my levers. Once I straighten them out, I imagine the buttons will spring back better, and I imagine the pallets will have an even tougher time closing all the way. Could you offer a solution, should this prove true?

Separately, I was thinking of picking up some materials from my local Hobby Lobby for refacing the pallets. Any materials suggestions? Thickness recommendations?
...

When the buttons spring back better the pallets have an easier time closing all the way actually. But should extra strength still be needed from the springs you can take out the bass mechanism again (to have access to the springs) and just tighten the springs without replacing them. Typically these springs have two "straight" ends with a coil in between. You can bend the straight ends a bit where they meet the coil to increase the angle between the straight ends and that increases the strength by enough to make a difference.
To replace the pallet felt+leather it's best to buy felt+leather from an accordion parts/repair shop. You should measure the current thickness of the felt+leather and then add perhaps 0.5mm or thereabout to compensate for the compression that happened over time. I buy all my stuff from Carini (www.carinidena.it) in Castelfidardo but there are other suppliers online as well. A hobby store (I don't know about Hobby Lobby) is unlikely to have the felt+leather sandwich ready made, and if you make it from separate felt and leather you risk using the wrong glue between the felt and the leather and have the glue penetrate the leather causing sticky pallets.

 

[oldbayan]

I've fixed many of these Hohner bass machines…they tend to jam …but I've always managed it without stripping them down completely. Well done.

Typical of small Hohners like the Student IV and V models! I think some oxyde forms on the pîston "blades" that make them jam.

 

[hoag]

When the buttons spring back better the pallets have an easier time closing all the way actually. But should extra strength still be needed from the springs you can take out the bass mechanism again (to have access to the springs) and just tighten the springs without replacing them. Typically these springs have two "straight" ends with a coil in between. You can bend the straight ends a bit where they meet the coil to increase the angle between the straight ends and that increases the strength by enough to make a difference.
To replace the pallet felt+leather it's best to buy felt+leather from an accordion parts/repair shop. You should measure the current thickness of the felt+leather and then add perhaps 0.5mm or thereabout to compensate for the compression that happened over time. I buy all my stuff from Carini (www.carinidena.it) in Castelfidardo but there are other suppliers online as well. A hobby store (I don't know about Hobby Lobby) is unlikely to have the felt+leather sandwich ready made, and if you make it from separate felt and leather you risk using the wrong glue between the felt and the leather and have the glue penetrate the leather causing sticky pallets.

I see the springs! Copy that.

I understand, and I also care to use the right materials for the right job. In my last correspondence with the Carini shop, I was informed that they were out of the felt/leather sheet of the thickness I was after. I was able to source good leather and good felt in the proper dimensions, and some spares in case of different tolerances due to age and compression.

Which glue would you veterans recommend for joining the leather to felt?
I assume there is a different glue for joining the sandwich to the pallet’s raw wood face. What would this one be?

Power was restored, but internet was not… My replies will still be sparse, for the time being.

Thanks, cheers!

 

[tcabot]

Vets will recommend buying the real stuff.

If you really want to make your own, you're better off using upholstery spray contact adhesive (the spiderweb stuff). Any other glue will penetrate the felt, harden and significantly degrade your sandwich performance.
The problem with using your own leather is that it's not as supple as the "proper" one. You can still achieve a seal, but it takes more alignment work.
On the other hand, if you think about it, you really want to have your pallets aligned really well, so using lower-grade sandwich means you have to do the alignment properly

 

[hoag]

I will still be ordering some more proper materials from the Carini shop, but I figure I can give it a go myself in the meantime.

Certainly, I can remove my handmade hoagie sandwiches and reface my pallets with the Carini sandwiches when they arrive, correct? Is there a poignant reason not to do this?

As mentioned in my first post, I am a luthier of some time, and I would love to have a deeper understanding of the components involved in accordion luthierie. I do not mind the extra dollar of double buying materials, so long as I am learning a relevant process to the craft. My experience lies mostly with double bass, cello, guitar, and electromechanical pianos. I have gone so far as winding a single pickup for a Fender Rhodes; I understand there are great pickups wound to spec that I could buy, and I would also care to understand that part of the whole.

I hope that my post does not read with any poise, I mean to explain why I push to add extra work, and lessen the feeling that you are all serving advisor to a brick wall.

I’m now in the process of cleaning my bass side pallets, as well as the air release pallet.

Thanks again!! I’ll follow up soon.

 

[tcabot]

You can remove & replace, but it takes a lot of time.
I've just re-built a box using my home-made sandwiches. Aligning the pallets was certainly a lot more difficult than with "proper" stuff. I don't know yet if my pads are as good at holding the air as the proper ones - will sort out the bellows gasket and check. It's a lot easier & faster to glue up home-made stuff than wait up to a month for a Carini shipment.

PA and CBA just have too many parts and too many reeds.
If you like fettling with squeezeboxes, a melodeon might be a wiser choice than an accordion. It's smaller and more manageable to work on. Also, there's no overly complex Stradella mech to deal with.
I'm building a melodeon from scratch, but I wouldn't go there if I were you. Quite a minefield - and I'm a guitar and mandolin luthier, so it's not my first decade working on musical instruments.

 

[Ventura]

(whatsan) ike gave me a good tip once about the glue and pallets
felt and leather routine..

to spread a very thin layer of your glue on the mating surfaces
and let them dry fully, then you will need less glue to get them
stuck together as the materual has already bonded with the glue
and now you only need enough fresh glue to get the two dry
glue layers to bond, lessening the chance of glue migration or
even just too much glue soaking in and making the materials
less pliable

 

[hoag]

Howdy, everyone!

Hurricane Milton has passed, and I'm back to some form of normalcy.

I've been tinkering away over the past couple of days, carefully measuring my materials and referencing forum posts via the local Taco Bell's wifi. I've been able to synthesize some felt/leather sheets that I believe will work.

I have removed the old felt/leathers from my bass side pallets, and I've sanded them all level. This did take quite a bit of time, as tcabot suggested, and I'm very glad that I went through with this process. I figure that instead of repeating this process once my proper materials arrive from Italy, I will go ahead and add some fresh pallets to my order. I'll do it all fresh, along with the treble side, when the materials all arrive.

I've slightly adjusted some of the worrisome bass pallet springs, as debra suggested. This has particularly helped my pallet lever action to feel better, and more like new!

I have fourteen pallets left to cut out from my sheets. I believe they're all sealing quite well so far, but the only way to tell is with everything reassembled and buttoned up.

Once I finish cutting out and fitting my freshly faced pallets, my next step is to wax them back to their arms.

Images coming soon!
Thanks for all the help, I think this will turn out wonderfully.

(Please continue to advise and critique, this project will be ongoing!)