Fix This! Instrument Repair, Inc.

Serving all of Chicagoland

746 East Northwest Highway
Palatine, IL 60074

Phone: (847) 359-4444

Mon: By Appointment
Tues, Wed, Fri: 10am - 6 pm
Thurs: 12pm - 7pm
Sat: 10am - 4pm
Sun: Closed
King 6B “Duo Gravis” Bass Trombone conversion from Dual Thumb Trigger String Linkage to Split Lever Minibal Linkages

King 6B “Duo Gravis” Bass Trombone conversion from Dual Thumb Trigger String Linkage to Split Lever Minibal Linkages

King 6B “Duo Gravis” Bass Trombone conversion from Dual Thumb Trigger String Linkage to Split Lever Minibal Linkages

Here at Fix This! Musical Instrument Repair we regularly get asked to do different things to modify older models of instruments to make them easier to use. For example, you may have already read about our 1st valve thumb hook additions our minibal conversions on our website.  We received an inquiry about we could updating a King 6B “Duo Gravis” Silversonic Bass Trombone from the original dual thumb triggers to something closer to what we see on the majority of modern bass trombones, the split lever system with minibal linkages. After doing some research and estimating the cost, the project began.

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Ou brass technician spent a lot of time considering making the whole project from scratch or modifying something that currently exists. Our retail side, Hornstash, deals in Getzen trombones, so we had the idea of modifying the lever assembly from the Getzen 1062FD Bass Trombone linkage for the D valve. While it would have been very simple to adapt an F lever as well, the span from the bell brace and the hand slide brass is much too small on the King 6B to just ‘plug and play.’ We decided it would be best to alter the current F lever as well as use the current lever saddle that has room for both levers.

There are many challenges with changing the linkage system. We started by altering the stop arm assembly, the part that directs how far the rotor turns and connects the rotor to the operating linkage. On the dependent D valve, it was possible to use the same location for where the linkage is mounted on the stop arm with a minor modification.

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This is a picture of the modified stop arm. It is necessary to make the linkage sit about the stop arm retaining screw in order to have proper clearance. It starts with a brass rod. The rod is filed down so it can be threaded with a die.

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It is cut to length and a hole is drilled and tapped in the center to take the screw to mount the minibal to the stop arm.

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The last part of this step is screwing the new part into the stop arm. We also soldered the connection for added strength.

For the F valve, a new connection was tapped and brazed in order to have the minibal connection work properly with the old F lever.

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An extension was machined in the same manner to have the proper length for the connection between the lever and stop arm.

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The F lever was placed on the outer part of the lever saddle and manipulated to be in a comfortable position for the player. The D lever had the hinge tube altered to sit in the lever saddle and bent to provide clearance for the F lever.

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With all the parts finally altered and work surfaces cleaned up, it’s time to finally assemble the trombone. Our customer was very pleased with the result.

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