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Servicing the Conn Microtuner

Ever had this problem? You've just spent 15 minutes carefully selecting and mounting a reed on your mouthpiece. With great care you position it just right and it blows like a dream. Five minutes into the gig and you're blowing a little you reach up to the mouthpiece to pull it off a little...and disaster strikes. The ligature slips, the reed skews and in your desperate rush to replace the reed you end up chipping the tip and ruining it. Wouldn't it be handy to be able to adjust the tuning without having to wrestle with the mouthpiece and its delicate reed?

Enter the Conn Microtuner.
The basic principle is simple; it provides a means of adjusting the tuning by way of a sliding mouthpipe, controlled by a threaded barrel. The tuning can be adjusted on the fly without having to touch the mouthpiece at all.
What a brilliant idea - but there are drawbacks.

Firstly, from a mechanical perspective there's a lot to go wrong. There's a long thread cut in brass which can wear; there's a sliding tube which can also wear and the whole thing is quite capable of locking solid with the ingress of all that gunk that you blow down the mouthpiece.
Secondly, there's the question of whether all that gubbins* affects the tone. It certainly does if wear in the mechanism allows a leak to develop.

Here's a picture of the Microtuner in all its glory...

Chu Berry MicrotunerA common complaint from Conn owners is that the Microtuner develops a rattle. This comes about through wear in the thread of the tuning ring, less often though wear of the sliding tube.
Worn threads can be difficult to can't actually replace the ground away metal - but there are one or two things you can do to improve matters.
You can either nip along to your friendly neighbourhood repairer and have them service the unit...or you can indulge in a little home maintenance. You might not be able to do as much as a professional, but at least you'll keep the unit from wearing much further and you'll prevent it from seizing up.
As mentioned, due to the amount of gunk that gets blown down a crook the Microtuner is inclined to lock up. In order to remove it and take it apart a certain amount of force must be used - but these parts are delicate - so I strongly advise you proceed with extreme caution and defer to more experienced hands if the unit proves at all difficult to move. Above all, take your time - patience is very much a virtue for this job.

There is more than one design of the Conn Microtuner. This article is based on the Microtuner as seen above, found on the Conn New Wonder alto (commonly known as a Chu Berry) circa 1926. The variations in design seem largely confined to the innards, specifically the tongued mouthpipe and the slotted receiver on the crook - as we'll see later. With a little caution and some common-sense you should be able to apply what follows to most Microtuners.
From here on in I'm working on the assumption that the Microtuner is stuck fast - if yours still moves, just skip over the bits that aren't applicable to you.

What you will need:

Chu Berry  exploded MicrotunerFreeing agent (Plus Gas, Liquid Wrench or some other penetrating 'rust-busting' oil)
Copper grease
A small screwdriver
An old toothbrush

What you may need:

A pair of bent Circlip pliers
A vice block

The very first thing you have to do is remove the octave key. You're going to be manhandling the crook a great deal and the last thing you want to do is bend that octave key. Remove the screw, lift the key off and put it in a safe place.
The second thing you have to do is remove the grub screw that holds the locking ring in place.
This must be removed to be able to move the locking ring. It's usually chewed up, so don't be surprised if you can't remove it - and if so it'll need drilling out...which is a job best left to the pro (again). If you can't remove it you can't fully strip the unit down - though you can still do a partial service.

This Microtuner is made up of three distinct parts: Note the holes in the tuning ring and the locking ring where the grub screw is located.

Chu Berry bare crookThe parts are pictured in order of assembly...the tuning ring or barrel fits onto the lower portion of the mouthpipe, and the locking ring screws into the barrel to secure the whole arrangement in place. It all fits onto a corresponding thread on the crook...

Notice how grubby it all is? This will give you some idea of how and why these tuners are prone to locking up. It's a gritty mix of scale (calcium carbonate - the stuff you find in the bottom of your kettle), verigris (brass corrosion), decaying lacquer and plain old grime.

Note too the tongues or slats on the mouthpipe and the corresponding slots in the crook, which help to stabilise the mechanism. On the left is the crook from the Chu Berry alto - and on the right is a shot of a crook from a 1950's Conn 6M Later Conn Microtuner(Underslung) alto. Note that there is only the one slot for the tongue on the mouthpipe, and it's now located on the top. This arrangement is also found on the earlier Mk.VIII 6M, though with a slightly less fancy tuning ring.

Below is the Microtuner arrangement for a Conn C Melody.
It's an early example of the design and you can see that it's rather basic compared to the later models - there are no slats to guide and support the tube that extends back from the cork, which tends to make the unit rather more wobbly in operation than the later models.

Conn C Melody MicrotunerNote too that the threaded locking ring is fixed to the cork tube. This is incorrect, and in fact the ring had been soldered on (back to front, as it happens). This meant that when the knurled tuning ring was turned, the cork - and thus the mouthpiece - revolved too. You can imagine how inconvenient that would be.
Although it's a simpler unit, the principles of operation are the same as the more advanced examples.

So, as with all threads, preparation is everything. Liberally douse the tuner with the penetrating oil. You'll be able to get some in from both ends of the tuning ring...and pour a generous amount down the crook too. Slosh it about a will help to free up a stiff sliding tube. A little topical heat will always help - those of you with flame guns can try a light flame (do this before you apply the freeing agent, it's flammable stuff!), or you can pop the unit under a desktop lamp and let it warm up for 15 minutes or so. Don't let it get too hot if you have any lacquer left on the crook.
You could also try slooshing it with vinegar. This will soften and dissolve any scale deposits that might be jamming the mechanism. Once again, a little gently heat helps the process along.
Looking down on the tuning ring from the mouthpiece cork, the ring turns anti-clockwise for removal. The first picture on this page shows the ring almost fully screwed on.

You should at least be able to turn the tuning ring. Try turning it both ways, this helps to break up any dirt on the thread which might otherwise compact and make matters worse. If it won't budge, then you'll need to think carefully about whether to proceed.
In order to shift a stuck tuning ring you'll need to 'get heavy'. If you're lucky you may find that the penetrating oil works its way into the mechanism over the next couple of days (I said you'd need patience)...and the ring starts to move. If not (or you just can't wait) you'll need some help with the grip on the ring.
A simple aid is a chamois leather - wrapped around the ring this increases your grip on it.
Another aid is the vice block.

The Vice BlockThis is a hardwood block with a hole drilled right through it.
The size of the hole corresponds to the diameter of the main body of the tuning a couple of millimetres. The whole lot is then sawn in half straight down the middle.
This is placed in a vice (it's tricky...a blob of blue-tak will help to hold the blocks in place whilst you position everything) and the tuning ring is placed inbetween the blocks. The vice is tightened gently. If the block faces meet too soon, saw a few millimetres off one face.

I can't tell you how much grip you'll's something you have to feel. The use of this block spreads the load considerably, so you can be reasonably firm - but if the ring still won't move as you try to turn the crook in the block then it's time to think again. As a last resort you can try a plumber's wrench on the ring, with the jaws wrapped in chamois leather...but this really is a last resort and you'd need to be extremely careful not to damage or crush the ring. If you're even the slightest bit unsure, take the job to a professional.

OK, assuming the ring turns you can unscrew it right off the crook. It may not come apart that easily once the threaded portion has been undone as the tube can be fouled up with gunk. A little bit of judicious wiggling about should shift it...or more heat and more freeing agent. Be patient - it might have been half a century since the Microtuner was last dismantled.

Now, at this point you have two parts in your hands - the main crook and the Microtuner unit (still assembled). You can either service the unit as it stands...or you can dismantle it further. The reason for dismantling it further is to allow for superior cleaning of the innards, plus a degree of tightening on refitting. Unless you've had the unit serviced recently I'd advise carrying on.

Refit the mouthpipe and screw the tuning ring back home (give it a quick wipe over if very gritty). What you need to do now is remove the locking ring on the outer end of the tuning ring.
You could have removed the locking ring at the start, but I find it helps to support the tuning ring if you encounter any resistance while trying to remove the Microtuner unit as a whole - and by refitting the unit you lessen the risk of crushing the tuning ring whilst battling to remove the locking ring.
This is where the vice block really comes in handy - clamp the whole thing in the vice block around the tuning ring, mouthpipe up.

circlip pliersThe ring itself has two slots cut into it - in order to unscrew the ring you'll need a pair of bent Circlip pliers (left)... and a good pair at that. They're not cheap...maybe £20-£30 for a solid pair...about the cost of having the Microtuner professionally serviced.
You might be tempted to use the blade of a screwdriver and a small mallet to gently tap the ring round. Unless you know the ring will move this will often result in your chewing up the slots. It's your risk.

All being well, the ring will turn (anti-clockwise again). Remove it, and then unscrew the tuning ring again. This time the ring will come right off the per the exploded picture earlier.

Now to set about servicing the unit.
Cleaning is the first order of the day. Use warm soapy water and your toothbrush to scrub every part of the unit you can reach - particularly the threads, the sliding surfaces and the bore of the crook. If it's really caked up with hard gunk then a light scrub with a brass brush is in order...but only a light scrub, those threads are delicate. Remember to clean the locking ring threads too.
It doesn't hurt to gently clean the sliding surfaces of the mouthpipe with a bit of superfine (XXXX grade) wire wool. Don't try to polish these surfaces - you'll just wear them down.
Alternatively, drop the whole lot into a bowl of neat vinegar for half an hour or so (try to keep the mouthpiece cork dry though otherwise it might smell a bit of vinegar for a few weeks). For further advice on using vinegar to clean parts, see the article on cleaning the crook.

If the sliding surfaces bind solid even when clean then you may need to have the mouthpipe lapped in - and that's a job for the pro. Try removing the mouthpipe and turning it 180 degrees (only applies to certain models)...sometimes it works better fitted one way up than the other due to the alignment of the tongues in their slots.

Assuming that went well and all the parts are dry, try reassembling the unit. Screw those threads home a few times to eke out any last bits of gunk - check that the mouthpipe may be slightly stiff, it's not meant to be too loose a fit.
Take it all apart again and get ready with the grease.

I recommend using copper based grease (bought in small tubes from vehicle accessory dealers). What you absolutely must not use is an organic grease, such as cork grease. This will encourage verdigris to form, and the unit will gunk up again.
Copper grease works very well - it's tenacious (it sticks), it's waterproof and the copper helps to coat the threads and keep them lubricated. It's also not too heavy - which would make the unit stiff in operation. If you feel you have excessive wear in the unit and you don't intend to adjust it once its all back together, or have it fixed, use a heavy grease.
Smear a dollop in the bore of the tuning ring, similarly on the locking ring and the sliding tube and slats. Use a matchstick to poke some grease right behind the slats.

Fit the mouthpipe to the crook and slide it to and fro...really work that grease in.
Mop up any excess, especially in the bore of the crook.
Remove the mouthpipe and screw the tuning ring onto the thread on the crook, work the grease in by screwing the ring fully on and off. Mop up any excess and screw the tuning ring on about two-thirds of the way home. Slide the mouthpipe into place and push it fully in.
Now fit the locking ring to the tuning ring and screw it in hand tight (with the slots upwards), again remove any excess grease. It can be a bit of a chore getting this ring back on, and if you force it you might well end up crossing the thread - which is completely bad news.
Now, about that grub screw. The hole in the locking ring is supposed to correspond to the hole in the tuning ring where the grub screw goes in. Wear and tear in the unit will mean that the two will probably no longer line up because the locking ring will need to be screwed in that little bit more.
This ring sets the tightness of the tuning ring (note: It does not take up wear in the tuning ring threads though) and can help to lessen any wobbles.
Use the Circlip pliers to tighten the locking ring little by little and keep checking the action of the tuning ring until it becomes too stiff to turn easily. Now back the locking ring off a little so that the tuning ring turns smoothly.

If you're lucky the hole in the locking ring aligns with the hole in the tuning ring. If so, refit the grub screw snugly. If not, I'd advise leaving the grub screw off - if you screw it down onto the thread of the ring it'll chew it up...and that will cause problems when you disassemble the unit again. The locking ring should be fairly tight anyway - but if not you'll have to find another means of securing it.
The proper solution is to drill a new hole - though even this can only be done a few times at best.
A reasonable fix is to degrease the hole (a drop of lighter fluid and a pipe cleaner) and drop a spot of threadlock down the hole onto the thread. Failing that, nail varnish will do the job.
An even better fix is to use a nylon grub screw...but when was the last time you came across a shop selling nylon grub screws?

Check the action of the tuning ring over its entire length of operation. You'll notice that as you undo it it becomes stiffer. This is because the thread is worn at one end. The grease will help to deaden the rattle this causes. More importantly, grab the mouthpipe and try moving it. It will move in and out very slightly as it takes up the play in the tuning ring threads - but it should not move from side to side. This would indicate wear in the sliding tube...and a potential leak.

Finally, refit the octave key - taking care to locate the flat spring in its little grooved channel on the surface of the crook.
And there you have it - one smooth, slick Conn Microtuner...good for another 5,000 bars.

*Gubbins. A slang term meaning 'lots of stuff'.


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