Pat fixed this wire issue and the hum is much lower now. I am glad it was this simple.
If you have a Clarinet or Cornet with hum you will want to try this. The procedure is to remove the back bell, take the wire going to the lower left bolt (the one with the star lock washer) and cut off the connector. Strip this back, solder or crimp on a longer wire making sure to wrap the joint so it doesn't short something.
Take this transformer ground wire directly to your star grounding point you selected for your Cornet.
On mine I use the RCA ground lug as the star location. The shortest ground wire is the green and yellow wire going back to the IEC power connector earth ground position.
Every ground on my Hagermans go directly to that RCA ground lug star point.
My Hagermans are dead silent. In fact my Clarinet, Cornet 2 and Piccolo are quieter than any other equipment I have ever owned.
Here is a picture of my Clarinet. On the right you can see the 8 Vampire direct gold plated OFC chassis connectors. I love these pieces. Then you see the RCA ground lug. I have 5 ground wires coming out there. One goes to the IEC plug earth ground connection (green and yellow), one to the tranformer (you can see the wire coming from underneath the board), one goes to the brass fuel rod I use to actuate the 4 pole source switch, one goes to the earth ground lug on the PCB and the other is going to the chassis itself.
In fact that wire is tied back to the front panel where the switches are mounted. If I have accumulated any static walking across my rug, I want it draining smartly back to the earth ground rather than finding some easier pathway to my circuit.
This is helpful in high static regions such as Reno.

This is a great way to handle the grounding on your Hagerman pieces.
BTW if any of you out there are pulling off those 4 bolts to expose the wiring under the bell covers you have nothing at all to worry about. Nothing falls out or comes out of adjustment.
When you finish splicing the wire, don't forget to switch the nuts and bolts so the nuts point out back.
ScottRT showed me that trick and it looks a hole lot nicer.
I painted my bells with Hammerite charcoal gray paint just for a nice twist. It looks like silver paint in the pics but it is actually a nice subdued charcoal color that matches well with the stainless steel handles I use to protect the tubes up top.
This is also a recommendation ScottRT made when I visited his home a couple years ago. Thank's Scott! That experience has dramatically improved my system.

Are these Hagerman projects fun or what?
Pat I agree that Jim should probably modify the owners manual to have each owner define a star grounding position and take every ground wire directly to that point.
Other than the RCA grounds touching the chassis, these seem to be the two most important points in getting the Hagerman silent.
And man are these things quiet!