Of all the types of repairs I carry out, perhaps the most exciting is the 'mysterious problem' - or at least its diagnosis.
Complete overhauls are almost no challenge at all - the instrument sits in its case looking tired and disheveled, there's little doubt what the prognosis is.
Likewise the 'general service' - puffy pads and ailing corks are easy to spot.
So too are specific repairs; dirty great dents, detached pillars and fitting enclosed in plastic bags, bent bodies and cracked joints.

But the mystery problem requires a spot of detective work.

The chap who brought his Yanagisawa tenor into the workshop summed up the problem succinctly..."The low notes don't work".
Even as the case (brazen pun intended) is opened I'm sussing out the job - the horn looks almost new, so maybe I'm dealing with a knock...or a dodgy setup.
The first port of call is the bell itself - a leak on the bells keys will scupper any hopes of decent low notes, but everything seemed to be in order there.
The next place to look is the G#. Because this is linked to the bell keys a slight misalignment of the mechanism here will seriously affect the low notes too, but once again all was found to be in order. A cursory look over the rest of the horn showed nothing amiss save for a paper disc that had been glued over the A key felt. It's common to find bits of paper stuck on keywork - musicians with a bit of technical know-how sometimes use scraps of paper to adjust regulation in emergencies (which then gets left on and forgotten about 'cos it works), though this bit of paper was a neat disc...hmm.

I got the cigarette paper out and went over the horn testing the pads for hidden leaks. I took the time to adjust the spring tension as I went along - why do new horns come out of the factory with such heavy actions? I'd love to meet one of the guys who sets the action up on new horns...if only to see just how meaty his hands are.

I noticed that the G key was clicking on its way back up. The buffer cork at the top of the key was a piece of that reformed, compressed cork. It's good stuff, in the right place - but on larger keys I feel it tends to promote key-bounce and noise, so I took the key off and fitted a nice bit of felt.
I refitted the key, oiled the octave key mechanism and tried the G key. That click was still there as the key came up.
I checked the G key guide - sometimes the sliver of plastic or cork comes out and the key barrel knocks against it, but all was well there.

And then something else clicked. I'd heard this sound before.

I got a scalpel and pushed it under the body octave key pip. Sure enough, it lifted up out of its hole.
At some point the soldered joint had given way and the pip was just sitting in the hole. Every time the G key was pressed air was free to escape up the side of the pip, hence no low notes. The clicking sound was the G key tapping the loose pip back against the body.

There are two common reasons why these octave key pips come free. One is old age - the solder sometimes breaks down and the joint fails, but this was no old horn.
The other reason is that the pip has been whacked....from underneath.
There's only one reason it might get whacked from underneath - someone has used a dent bar to pop out a dent in the body, and has been rather careless about keeping the dent bar off the internal tube.

I took a look down the horn in a line with the pip and sure enough, just beside the low F tone hole was a slight ripple. The bore had a corresponding mark in the same place.
It ties in nicely with the paper disc on the A key - most likely a piece of paper peeled from the backing of an old clarinet pad.
It all adds up to a previous job done by a sloppy repairer.

I fixed the pip in with superglue.
Why not resolder it?
The pip doesn't suffer a lot of stress, and as the horn was almost new there's a risk of losing the finish round the pip if a soldering gun is taken to it. I really don't know why manufacturers don't glue it in - it would be a great labour (and finish) saver for us repairers when dealing with dents in the body.

The glue was set before I'd even got the octave key mechanism back on the horn - and a quick blow revealed a lush set of bell notes - and a new article for my Notes section.