HM-8030-4
Nothing electronically wrong with this one. Only 2 broken potmeter shafts.
The new and broken shaft
I removed the potmeter and then the broken shaft. Measured it and made a new one from brass. Why brass ? Just because I had 4mm hex stock and brass is very easy to machine.
One of the repaired potmeters remounted in the frontpanel PCB
At first it did not work but reseating the IC’s fixed it. It goes from 0,3 Hz upto 3 MHz, 20Vpp open circuit and amplitude is flat over the whole range.