Audio - Mains noise

[Doodski]

Not sure how big of a factor corrosion is as I have noticed some green and dirty-looking metal which I think might be aluminium corrosion. it appears to be surface tho

With the small signal levels of phono operation and the need for very good grounding and signal path integrity corrosion is definitely something to investigate.

 

[Fascinated Viewer]

With the small signal levels of phono operation and the need for very good grounding and signal path integrity corrosion is definitely something to investigate.

Soo, I am looking into this issue, and I noticed no circuits are used for the tonearm. Its just wires to phono female, and the ground wires are grounded to the metal stem of the tonearm, and the other makes its way at the top of the tonearm, but I can't see the other connection tho

 

[AnalogSteph]

Sounds like that's how it should normally be. The tonearm tube is being used as an electrostatic shield. There should be no buzz when you're touching the tonearm. Ideally the entire cable run up to the outputs should be shielded (but never making contact anywhere), so there is slight room for improvement by DIY means here - we'll think about that later.

The main problem area that'll cause hum issues tends to be poor contact at cartridge or headshell (if any). The contact surfaces are often silver plated and will tarnish over the years. Also, there are some cartridges like Grados that will connect L and R ground returns together internally, which results in an internal ground loop, so maybe check that with a multimeter, too.

Remove cables from cartridge carefully using small needlenose pliers. Take a reference photo beforehand so you know which ones goes where (there's a standard color code though AFAIK).

BTW, I am pretty sure that this wannabe "DJ" 'table dates from the late '90s / early 2000s. At a massive 3.75 kg, I am sure the plinth is leaving much room for improvement via bitumen mat and whatnot.

 

[Fascinated Viewer]

Yeah, I notice when I touch the phono cable's metal housing that the noise does quiet down a lot and looking at the copper in the headshell has two surfaces. One is copper, and where the two prongs touch, the needle is plated. I imagine with Nickel/silver, but unsure. Anyways the copper appears to be tarnished, so I imagine the silver is too.

I bought this record player on eBay for £15 so am not complaining about much plus I came with a stylist but I end up replacing that with a new one from audio Technica but I have not replaced the cartridge (the metal thing that the needle pluggs into) and I imagine it is pretty old. Also, the manufacturing date on the boards is 1999

 

[Fascinated Viewer]

I have tested the 12 v ground and that reads

With the small signal levels of phono operation and the need for very good grounding and signal path integrity corrosion is definitely something to investigate.

So the cartage is ground looped and there is 800 om's of resistance through from the cartage ground to the 3.5mm cable

 

[Fascinated Viewer]

After the turn table (so the aux cables) the resistance is 250 so it is something to do with either the cartage or the wires?

 

[Doodski]

I have tested the 12 v ground and that reads

Not 100% sure what you mean by this comment.

So the cartage is ground looped and there is 800 om's of resistance through from the cartage ground to the 3.5mm cable

Not 100% sure what you mean by this comment.

After the turn table (so the aux cables) the resistance is 250 so it is something to do with either the cartage or the wires?

If you mean the RCA cables they should measure at zero Ohms. From the phono cartridge wire connections to the tips of the RCA cables the resistance should be zero Ohms. The meter will probably read something like 0.6 or 0.9 Ohms.

 

[Fascinated Viewer]

Not 100% sure what you mean by this comment.

Not 100% sure what you mean by this comment.

If you mean the RCA cables they should measure at zero Ohms. From the phono cartridge wire connections to the tips of the RCA cables the resistance should be zero Ohms. The meter will probably read something like 0.6 or 0.9 Ohms.

So I tested the tonearm wire, which is 36 AWG (American wire gauge) and is made of silver which tarnishes easier and appears to be no good. The rest of the system seems fine same for the stylist wires (which reads 0.7 Ohms). The tone arm and brass housing are grounded to the turntable, which is fine and has a low resistance am currently looking at replacing the tonearm wire with either "pure" silver wire or copper. I guess either the strains of wire are broken or it has just tarnished over time.

I did test the RCA cables whey all seem fine