Oktava 319 with hum issue.

[RichardP]

Hi,

I have a Joly modded Oktava 319 - but have unfortunately dropped it. It now hums at 50 hz. It would seem that I now have a grounding connection issue.
I have noticed that if I touch the base of the microphone with one hand and the top of the basket with the other the hum disappears.
However, if I touch the base of the microphone with one hand and the side of the basket with the other, it makes no difference to the hum.
Would this suggest a connection issue between the top and the side? Certainly, the original epoxy has worn down a little (the mod is nearly 16 years old).
Could there be anything else that might explain the hum ( the screw in the centre of the diaphragm is stable)?

Much appreciated

RichardP

 

[pasarski]

Definitely sounds like you diagnose is correct

Edit: Would expect more like a buzz than hum though. But the fact that grounding the head basket with your hand makes the noise go away nevertheless implies it's a grounding issue.

 

[RichardP]

Thank you for your reply. (I guess it is more like a buzz than hum)

I've tightened the screws on the head basket which did not change anything (and other screws as well)
I guess I should look around Pin 1 and also consider re-expoxying the top mesh to the basket (given that only touching the top mesh in combination with the xlr shell seems to take away most of the noise).
Is there anything else you could recommend that I should be looking at in the first instance?

Many thanks

 

[Khron]

also consider re-expoxying the top mesh to the baske

Just keep in mind that normal epoxy is NOT conductive (and you WANT the headbasket connected to the mic body / chassis and ground)...

 

[k brown]

Just keep in mind that normal epoxy is NOT conductive (and you WANT the headbasket connected to the mic body / chassis and ground)...

Ya need that abnormal stuff:
https://www.amazon.com/Silver-Bond-...+epoxy&qid=1728133359&sprefix=,aps,178&sr=8-7

 

[RichardP]

Thank you all for your advice and support.
I will endeavour now to try and fix it.

 

[gordon]

We sent an AKG414C in for repair to AKG and when returned the microphone had the self adhesive copper tape around the areas that the grill contacted the main body plus additional ground wires added to give solid electrical grounding to the mesh wach side. The very high impedance at the capsule is sensitive to electrostatic feilds making effective grounding mandatory.