Home Mandolin Tuner Repair Hospital


   The tuner is an essential part of the instrument, and relatively high precision, in order that it works well under some tension, so it is not always possible to repair damage to them, but some basic repair work can be undertaken successfully. Very little equipment is needed, but an understanding of how they work and are put together is essential, so if you haven't already..... before starting, go and have a look at the tuner anatomy page!! If you need help, drop me a line on the Contacts Page.

Typical damage

  Here a mandolin arrived with mismatched tuners, probably because one side was ruined.    This is the result of rust. The tuners were completely seized, and could only be removed by disassembling. Only possible where cogs are secured by a screw!!    Perhaps, most common.... here the buttons have broken and been lost.
   Here a cog is missing, easy to fix in this set as they have screw-held cogs, if one is able to find a replacement piece.   In this aluminium set, the housings that hold the tuner spindles have given way.  In this old set, the tubular brass barrel, made by being folded over at the outer end, has split open under turning pressure.
Tuner Anatomy Jammed Tuners Enclosed Tuners
Tuner Buttons Main tuner pages Tuner Cleaning


Repair of Tuners
Outer Barrel Repair

It is possible to make a new outer tuner barrel, if you can find brass tubing of the correct diameter. The tubing I use has an outer diameter of ?mm and an inner of ?mm.


Once cut to the correct length, place over the inner tuner barrel in order to locate the correct height for the retaining pin hole. Then drill the string hole. It will be necessary to secure in a vice to do this.
Missing retaining pin

Occasionally I find a loose tuner barrel caused by a missing retaining pin. The easiest way to replace this is with a simple piece of nail. The nails I use must have some lead in them as they bend, and cut relatively easily.

More importantly, once the new pin is cut and fitted, a little longer than the diameter of the barrel, it can be hammered to spread the ends. It is this which actually holds the pin in place and the two barrels together.
Detached worm gear

Often, under string pressure, especially if something is out of alignment, the housing that hold the worm gear are forced out of the tuner plate. It is possible to refit these sometimes, if there is not too much damage.

 First make sure the plate is flat. Then file back the 2 lugs at the base of each housing. Squeezing with a pliers helps as you do not want to reduce the volume in the lug more than necessary. When it can be forced back into the holes, expand the lugs with a hammer to fill the holes, in a similar way as with the barrel retaining pin.
Missing Cog

Sometimes you will find tuners with a missing cog. This is perhaps the most difficult repair.

Missing worm gear
Jumping Cog

Sometimes you will find that the thread of the cog or worm or both are worn, and the tuner 'jumps' under string pressure


It is sometimes possible to remove the string barrel and cog as above, and clean up the threads, but it doesn't always work. NOTE: I have found that tuners which jump in one direction, sometimes will work in the other.... a last resort, but better than being unable to tune it.