Have you tried a wooden headshell?
Probably not the problem, just to know: Ortofon cartridge wires are slightly different diameters at each end
Ortofon SH-4 headshell and Ortofon cartridges’ terminal PINs diameter is 1.2 mm, whilst Ortofon headshells’ PINs diameter is normally only 1.0 mm.
................................................
My Blackbird Tonearm, using RCA,s (4 wires) have a junction box converting tonearm wires left/left ground and right/right ground to the RCA jacks. Notice, the mini din connector is only 4 wires (not 5 pin din).
AND there is a separate ground wire from the tonearm base to the junction box’s ground terminal. That’s like the 5th wire of a 5 pin din connector. Perhaps you can make a separate ground jumper and try grounding the arm.
