Help with basic Thorens TD-160 problem

[Chris Balton]

I have a very (hopefully) simple but annoying problem with a Thorens TD-160 that I recently purchased from ebay. The problem is one stereo channel that comes in and out intermittently. Please excuse me if this is a dumb question – but I am new to Analog.

I first thought it was an alignment or cartridge problem. So I replaced the cartridge with a new Shure M97xe. I have adjusted the vertical tracking force with a Shure gauge. I checked the VTA and the azmith as best I can. I ran a new ground wire form the chassis to my preamp. None of this has helped – if anything the problem has gotten steadily worse.

I checked the wires from the head-shell to the RCA jacks with a ohmeter and all the connections had around 0.6 ohms. I also switched the channels left to right at the pre-amp and the problem channel also moved – so it looks like the preamp is ok.

I thing I did notice that seemed odd was that one channel has one side connected to chassis ground and the other channel has both side un-grounded. What is the preferred wiring for this – both sides un-grounded and a separate ground wire or one side grounded on both channels?

Thanks for any advice.

Chris

[Keithj]

I've one of these, albeit with a Grace 707 arm. On mine, no feed from the cartridge is grounded on the turntable chassis; it only has a mains earth connection. I treat the cartridge as balanced and do any earthing only at the preamp end.

You didn't tell us what the arm is. Is it the Thorens arm or some other?

It's also possible that the contacts between the headshell and arm are corroded or that one or more of the little spring loaded contacts in the arm (if fitted) have lost their tension.

cheers, Keith.

[ken.berg]

Regarding your grounding question, I assume you've looked at the TD160 service manual posted at

http://www.theanalogdept.com/images/...e06%20copy.gif

I would suspect the cutting in and out is an intermittent connection either at a solder joint or inside a cable's insulation. Clip your ohmmeter between the cart clips and the phono jack and start <gently> wiggling wires and cables until you see something respond. Don't forget to check both the hot and ground sides (4 tests in all).

[Chris Balton]

Thanks for the suggestions. I have a TP16 tonearm, the early style that has a one piece arm.

I tried checking the wires again with an ohmeter and gently tugging on them - no results. So I went ahead and bit the bullet and rewired the output cables with new shielded cables in a balanced configuration with no signal ground. The ground now is isolated to the shield and back to the pre-amp through a separate wire. I made sure that the shield was only grounded on the turntable end - not the amp end.

For one day I thought I had the problem solved - it sounded great. Now the noise and loss of one channel is back. The problem must be inside the tonearm or at the headshell to tonearm connectors. That connector appears to be riveted or pinned to the tonearm. Has anyone replaced this connector and wires on an early TP16? The analog department website has instructions for replacing the wires inside the later tonearm, but this one looks more difficult.

Chris

[Netlist]

Did you clean the contacts inside the connector as Keith recommended? Check with a small screwdriver if the springs behind the contacts work. Be careful not to scratch them.

/Hugo

[dnsey]

Be careful when checking resistance / continuity - a cartridge is easily damaged if DC is passed through it.