Micro Seiki MB-18 issue

[MusicMan_ZA]

I first wanted to ask this question privately, but then though that others may also benefit from the answers if I ask it here  :thumbs:

My new MS MB-18 has a hum - as follows:

- arm in the up position
- from 0 to 5 on my amp's volume (it goes to 10) there is absolutely no hum
- hum starts at 5 and increases up to 7
- at 8 there is a high-pitched screech and my amp cuts out (speaker protection?)
- my normal listening level is 4-5, and even up to 6 there is no discernible noise whilst playing a record

I have tried:

- 3 different cartridges
- cleaning the headshell contacts
- fitted new RCA plugs

The RCA lead is a flat 3-wire affair with the earth between the L and R. The earth lead (middle wire) is also shielded, and the core and screening is twisted (soldered) together.

I have tested the earth from the outside tip of this cable to:

- the metal of the arm
- the metal of the (inside) top-plate
- the metal of the platter bearing

and there is a solid "connection" between all of these - as I believe there should be.

My question: what else should I look at / what are my next steps?

Thanks,
Johan

 

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