I am moving this over from another post, as this might be the more correct place.
I am having an issue with "hum" on my "new" Thorens TD125 Mkii turntable, and don't really know what to try next.
When I got the table, there was a hum, and one channel was "dead". The table had two RCA leads and an earth lead. All were connected as they should be (on my amp's side).
Because of the dead channel, I replaced the 2 RCS leads with new leads (from a regular el cheapo 2RCA to 2RCA 5m cable from Hi Fi Corp that I cut in half to create a 2.5m 2RCA lead from the tt to my NAD amp). All connection were tested with a multi meter to check for connectivity and leakage - all seemed fine.
Both channels now worked, but there still was a hum.
Trouble shooting commenced. Vinyl engine service manual was downloaded. Schematics were studied (with my knowledge, this does not say much!).
My tt has three wires coming out of the tonearm - left channel live & earth (core and screen)(one), right channel live & earth (core and screen)(two) and an earth (three).
Left L&E connects to one RCA lead, Right L&E connects to another RCA lead. Earth connects to a grounding screw (going to the solid bottom plate) on the small connector strip between the tonearm wires and the RCA leads. The grounding screw also connects, with a "jumper", to the screen (ground) of the one (right) channel.
There is also a wire coming from a post on the PC board going to the grounding screw on the connecting strip.
I noticed that there was a connector to the suspended top plate which was not connected to the grounding screw on the connector strip. I attached a wire to ground the suspended top plate to the solid bottom plate.
I still have a hum.
Disconnecting the separate earth lead coming from the ground screw on the connecting strip (and which goes to the amp) reduces the hum from a deep hum to a higher-pitched "screeching" (but softer) hum. Reconnecting it brings back the "deeper" hum.
Disconnecting the earth wire from the PCB to the ground screw makes no difference, either way.
Disconnecting the ground wire from the suspended top plate to the solid bottom plate makes no difference, either way.
Disconnecting the jumper from the earth screw to the screen (earth) of the right channel wire coming from the tonearm makes not difference, either way.
Connecting another jumper between the Right earth and left earth wires coming from the tonearm makes no difference, either way.
Without the head shell attached there is a huge hum, and with the head shell attached there is the softer, but more "screeching" hum.
Just about at my wits' end - what more can I do? This hum must be able to be eliminated!
J
I am having an issue with "hum" on my "new" Thorens TD125 Mkii turntable, and don't really know what to try next.
When I got the table, there was a hum, and one channel was "dead". The table had two RCA leads and an earth lead. All were connected as they should be (on my amp's side).
Because of the dead channel, I replaced the 2 RCS leads with new leads (from a regular el cheapo 2RCA to 2RCA 5m cable from Hi Fi Corp that I cut in half to create a 2.5m 2RCA lead from the tt to my NAD amp). All connection were tested with a multi meter to check for connectivity and leakage - all seemed fine.
Both channels now worked, but there still was a hum.
Trouble shooting commenced. Vinyl engine service manual was downloaded. Schematics were studied (with my knowledge, this does not say much!).
My tt has three wires coming out of the tonearm - left channel live & earth (core and screen)(one), right channel live & earth (core and screen)(two) and an earth (three).
Left L&E connects to one RCA lead, Right L&E connects to another RCA lead. Earth connects to a grounding screw (going to the solid bottom plate) on the small connector strip between the tonearm wires and the RCA leads. The grounding screw also connects, with a "jumper", to the screen (ground) of the one (right) channel.
There is also a wire coming from a post on the PC board going to the grounding screw on the connecting strip.
I noticed that there was a connector to the suspended top plate which was not connected to the grounding screw on the connector strip. I attached a wire to ground the suspended top plate to the solid bottom plate.
I still have a hum.
Disconnecting the separate earth lead coming from the ground screw on the connecting strip (and which goes to the amp) reduces the hum from a deep hum to a higher-pitched "screeching" (but softer) hum. Reconnecting it brings back the "deeper" hum.
Disconnecting the earth wire from the PCB to the ground screw makes no difference, either way.
Disconnecting the ground wire from the suspended top plate to the solid bottom plate makes no difference, either way.
Disconnecting the jumper from the earth screw to the screen (earth) of the right channel wire coming from the tonearm makes not difference, either way.
Connecting another jumper between the Right earth and left earth wires coming from the tonearm makes no difference, either way.
Without the head shell attached there is a huge hum, and with the head shell attached there is the softer, but more "screeching" hum.
Just about at my wits' end - what more can I do? This hum must be able to be eliminated!
J
