Oct / Nov 2003
Hearing Aid Repair & Modification Using UV Materials
Cracks in the Shell
Have you ever worked in a fast paced environment that demanded you get
things done quickly? I once worked in a repair lab where my numbers were
looked at every day, and if I didnít get at least a certain number of
hearing aids repaired I heard about it. That type of mentality just
wasnít conducive to my work ethic, but it made me want to take shortcuts
sometimes, which I felt sold the customer short. "Hey, they sent it in to
have the volume control replaced Ė what are you doing fixing the crack in
Oh, I can understand the question. This is a business and the more
repairs we can flush through the more time we have to work on more hearing
After all, they werenít complaining about the crack in the shell, and I
think for the most part they donít. A crack doesnít impact the sound
quality, and it was probably caused by being dropped or partially stepped
or sat on, so most customers feel it is their fault anyway. But still, if
it can be repaired quickly and easily what a testimony to the service they
received. Iíll give you my own testimony about this in a moment.
A definition is a good place to start
First of all, a cracked shell can mean a variety of things. It can
exist by itself as a single line appearing in the shell, or it can be as
complex as a spidering behemoth emitting from a hole or puncture. But
whatever the shape or form, a crack is tiny separation of the shell
material resulting in a visible line in the shell cause by some physical
The common "new guy" mistake
The first time I tried to fix a cracked shell I thought it was going
to be a cakewalk. I thought, "Iíll just slap some lacquer on this and
be done with it". Well, it doesnít quite work that way. The reason the
crack is visible is because there is actually a minute space where the
shell is separated. I found out the hard way if you try to cover a crack
with lacquer, you will end up with a nice shiny crack. If you try to cover
up a crack with thicker gel or shell material you can cover the crack, but
the hearing aid will probably not fit any more. To make the crack go away
the space needs to be filled with something, not covered with something.
Choose your method
Letís go the easy route first. The first thing you need to figure out
is if you can get any thin UV material, such as
Fotoplast-Lacquer, to seep
into the crack. If the crack is wide enough to do this then your job is
just about done. Just a tiny bit on the tip of the application brush is
all you need and if it migrates into the crack simply place the unit under
the UV lamps and it will be done in a jiffy.
If you canít get the lacquer into the crack, then it is time to bring
out the big artillery:
Sometimes you need to destroy something to make it better. No, this is
not a political statement. If you canít get the lacquer to migrate into
the crack, you are going to need to make the crack bigger so you can get
some material in there. Using a dremel tool and small burr, carefully dig
along the crack. You are probably not going to dig all the way through the
shell as you may damage some internal components. Just go deep enough
where you are almost going through the shell. Now, the slot you end up
with is probably going to be too wide to fill with lacquer so you will
need to patch this with shell material, such as
Fotoplast-Gel. And you already know how I feel about matching the color,
especially in this situation. If you are going to use clear on a colored
shell you may as well leave the original crack alone Ė it will look
better. Once the crack is filled, place the unit under the UV lamps and
let it cure for a minute. Wipe any oxidizing layer with an alcohol wipe
and buff smooth.
What About That Spidering Behemoth?
If you have a shell with a puncture or hole with spidering cracks you
are going to need a little patience. Your gut instinct is going to be to
go after that hole first, and that may work if the hole is small. In fact,
if it is small enough you can drill it out Ė including the cracks if they
donít go out very far Ė and patch it like we discussed in the
Newsletter. But more than likely the cracks reach further then that so you
will need to deal with them first.
Work from the extremities is the motto here. Using the same
techniques as above try to seep some lacquer into the far end of the
cracks. After the cracks are filled and cured, then tackle the hole as we
discussed in our September Newsletter.
If you need to do some other internal work on the hearing aid anyway,
by all means cut the hearing aid open first before trying to fix the
shell. It will make things a lot easier.
Oh Yeah, That Testimony
So is this all worth it? I mean come on, fixing that small crack in
the shell when you didnít really need to? Our company received a hand
written letter once from a woman who had sent in one of her hearing aids
because it wasnít working. She was so thankful to get it back, but that
wasnít why she was writing. She was certain there had been some mistake.
She thought she had received a brand new hearing aid because the one she
sent in had a crack in it. She didnít know she was talking to me, but I
remembered her name and remembered fixing her hearing aid.
It was worth it to me - and to her.