Thornes TD160 hum problem fixed
I just recently purchased very nice Thorens TD160 MKII with Isotrack TP 16 MKII with TP 62 arm wand with aftermarket interconnect cabling. Mechanically the table was excellent just needed cleaning up. Upon installation of my cartridge (Signet TK5E) there was a significant hum (60HZ) problem as soon as power was applied to the table. Two problems surfaced , one the interconnect cabling was not shielded, and two the capacitor across the 33 and 45 switch which allowed AC to be applied to one half of the motor windings. The schematic wiring for 110 ac from the Thornes manual show the phase capacitor as 0.33uf, and the pop suppression capacitor as 0.01uf. I changed the phase cap to 0.33uf from the 0.15uf that came with the table and the motor ran but with cogging, do not change the 0.15uf cap if that is what came with your table. Also my table was wired differently than the schematic showed. I then changed out the 0.0022uf pop suppression cap my table came with to the recommended 0.01uf, which caused an increase in the hum problem, which is understandable as it increases the leakage current to the motor. So I removed the pop suppression cap. The second thing I did was to replace the unshielded interconnect with a shielded cable to RCA jacks mounted in the back side of the chassis.
The turntable is now dead quiet and hum free. I have also cleaned and tuned the suspension and built a new bottom board from Ĺ in plywood, polished the platter, and replaced the belt. I personally like the ability to change interconnect cables to my preamp (modified Bugle 1) as I believe with MM carts. cable capacitance makes a difference and can tune the carts. high frequency response with a cable rather than changing input capacitance on the bugle (150pf). This way when I change to my Grado cart. or a different MM I can use different interconnects. Some people believe the extra connection degrades the sound, I canít tell the difference myself. The only issue is the tone arm, or I should say the TP62 arm wand it is really a pain to get it set up, and I question the stability of the set up. The bearings and the arm itself seem to be good. So how does it sound, compared to a SOTA table with a MMT arm the Thornes has better dynamics and a smother musical sound. The only thing I would change is a less fussy arm maybe like a Rega. O by the way I do not get any pop or noise when I switch the power switch on or off. My recommendation is if you are experiencing hum problem with your TD145 or 160 series Thornes remove the pop suppression cap and see if it helps without any negative effect, the motor is only a 10 to 15 watt motor so I donít think it will be a problem with the micro switch contacts.