Pink Triangle PT Too motor noise problem

[IanAS]

I have a friends PT TOO to fit a Denon DL304 for him.

Is it normal for the motor to make a huming that is easily audible?

Either turning the platter or on it's own.

It's the latter motor like the Linn have. On the black wood (look?) plinth.

There's pleanty or torque there. I need to press the pulley fairly firmly to make it stop, where upon it hums louder. Then oscilates when I hold it stationary.

It changes speed as it should by successive presses on the button. The hum changes pitch with the two speeds.

The PSU is the crinkle finish metal box with the vent in the top and the 5 pin DIN to feed the deck.

I've put the multi meter across the motor coils which were fine last week anyway. Measured Ohms to what I was told they should. Can't remember right now what that was.

Wiring to the motor, switch and through the lead measured OK.

The PSU was a bit dodgy and has had a few capacitors replaced and was working fine.

Maybe it always hummed and no-one noticed before. The metal plinth top acts as a sounding board!

And also noticed the platter bearing makes a slight grinding noise (sounds like a quiet hiss when turned by hand without the belt on). I've cleaned it with evaporating brake cleaner aerosol and lubed with white greace to no effect then with copper slip, also to no effect.

Thanks for any advice

[NAT.D.BERG]

Thought I'd revive this thread to see if anyone else joins in..

I'm trying to sort out a PT Too at the moment and been looking at the three PSUs I've collected.. I have one dead one, one slow one and one working well.

Mine also makes a fair bit of noise motor-wise but less so on the good PSU! The output to the motor seems to be through a simple TDA2004 based amplifier circuit and the variable resistors create a potential divider accross the capacitor on each input to this amp circuit.

Now, I know nothing about circuits except what I learned in Physics and general picked-up knowledge but my guess is that the potential dividers might change the phase angle of each input which would effect motor noise. I'm not sure.. so I may take an oscilloscope to it and see.

The other thing to know is that the thrust bearing on the bottom of the motor can effect its noise - normally a white plastic housing on the back. I have a separate motor with a thrust bearing that can be adjusted by a screw and tightening that up also cures noise - I guess over time the whole mechanism in the motor drops and vibrates more?

Regarding the platter/bearing noise, if you don't mind taking the deck apart and putting the sub-shassis, bearing and platter together on their own you can really hear any noise going on very clearly. Hold it flat in the air while the platter spins and the aerolam acts as a sound board for any vibrations. I have a spare bearing and so was doing this to decide which to use - there was little difference (apart from actualy fit of the nylon collar rattling around) but I used vasaline as a lubricant and suddenly much noise dissapeared.. Perhaps a thicker lubrication is better for an inverted bearing?

Anyway, they are my thoughts!

P.S. NEVER turn on the PSU without a load connected i.e. the motor as if will then die like mine did.

[IanAS]

Thought I'd revive this thread to see if anyone else joins in..

I don't think they will, it's been three years!

The potential dividers might change the phase angle of each input which would effect motor noise

There are different versions of power supply. My pals one is an original prototype it seems. Are yours all the same?

The other thing to know is that the thrust bearing on the bottom of the motor can effect its noise

I just oiled it I think.

I used vasaline as a lubricant and suddenly much noise dissapeared.. Perhaps a thicker lubrication is better for an inverted bearing?

I think the white grease I used may be thinner and the copper grease thicker than Vasaline. Normally a special oil is used for such a bearaing. Manticore supplied some with my deck.