Discussions > Instrument Design, Construction and Repair
Leaky HA114
aislingean:
I have an air hungry HA114 in G that has leaks in the growl box chambers on push.
The fixing screws for the growl box are below the timber reed blocks that are glued in.
Is there a recommended method for resealing through the spoon holes. ?????
Wax, Liquid resin, PVA, Alphatic resin, bead of silicone sealant, decorators acrylic caulk ????
The end-plate under the strap appears to be housed in a groove and can flex slightly.
Existing sealant has cracked and left a fingernail gap!
I imagine this is a fairly common problem on these older Hohners.
All suggestions gratefully received.
cheers
Dave
Theo:
The get access to the screws just remove the reeds and the screws are usually then accessible.
I would not recommend attempting to seal through the spoon holes, too much risk of getting sealant where you don't want it - on the reeds especially, and not being able to reach all the leaking joints. I'm not clear from your description where the leaks are from, but if it is the joint between the growl box and the plate it mounts onto then it is not a big job to take of the reeds, remove the screws, take of the growl box and replace the gasket, then re-assemble. Its always better to do the job properly first time.
The most common area of leaking on these is from the bass spoons themselves, and if it is mainly leaking on push then that is by far the most likely source of leaks. To fix make sure you have:
The spoons lying completely flat when closed (they easily get bent)
good quality springs (they can break and may have been replaced with poor substitutes)
good pad material on the spoons (the original stuff gets hard)
aislingean:
Thanks Theo!
From here on I am 'Thinking out loud'
One screw is definitely under the base chord block timber! [The edge of the head is just discernible]
Two screws I can see and one is probably accessible under the single note reed-plate but the air leak is definitely between the grooved sides of the growl box and the strip of timber that sits in the grooves and forms the end/base of the box under the strap.
Two spoons are new and all have been checked and are sitting flat.
Holding spoons lightly closed and gentle push gives jet of air that can be felt on face or hand.
Bellows is airtight and treble side has no leaks.
Straps off ....suspend box .....bellows extends as there is only small vacuum
Growl box to [silver papered] end plate is air tight.
I had thought that as the reeds will be above the work area it would be safe to work though the spoon holes.
I was reluctant to disturb the reed plates un-necessarily and had envisaged working with a syringe and flexible tube outlet to position sealant along the original joint line.
I favoured non acidic silicone as it will have a degree of structural adhesion and will flex with the timber but pouring wax or resin would seal the joints and alphatic would sink into the open joint and give structure but it has no gap sealing properties.
Hot glue either traditional or synthetic would not be as controllable, whereas Pva would whilst being controllable require a long curing time and would collect dust as it retains a surface tack. The acrylic caulk would seal any gaps and being easily reversible may be the best route to try at first but it will give no improvement in structure.
I had thought that this repair would have been a common one with a 'standard' solution'
Never mind I am on a voyage of discovery
cheers
Dave
Theo:
Now I understand where the leak is. I've not previosly seen an air leak in this location. I would still favour removing the growl box, shaving some wood off the reed chambers if necessary to reach fixing screws. I would probably favour a bead of pva along the joint, applied from the inside. If I could only work from the outside I think I might use superglue which has the advantage of a capillary action that draws it into the cracks.
aislingean:
I will report back after she is completed however I am in no rush so don't hold your breath!
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