Vestax PDX-2000 Anti-Vibration Service Bulletin

On 18th February 2003 Vestax released a service bulletin for PDX-2000 users who experienced vibration in the platter when the record was being held. 

Here's a bit more detail as to what the issue is, which turntables are affected and how to implement the fix.

"When the platter is pushed down and a fair amount of pressure is applied (during scratch play), the platter may generate a vibration. This problem occurs on units produced in the first few batches."

These are the affected units:

 Original Mains Voltage of the Unit Earliest S/N Latest S/N
230V 07N010201  23N380500
120V 07U010401  23U380700
100V 07F010001  22F370300

 

If your turntable is one of the above and also has this issue then here's how to implement it, please be aware you need to be confident and capable in de-soldering and working with electronics.

Unplug your turntable and leave it for a while to safely discharge the voltage stored in the capacitors.

Remove the platter from the turntable, place the M3 pan head screws somewhere safe.

Using a wide saucepan or wok, flip the turntable upside down ensuring it's carefully balanced and that the tonearm is not touching the surface.

Remove the rear cover and place the screws somewhere safe.

Take your time and photograph the turntable insides, note where each connector and ground cable go, you'll need to remember this for re-assembly.

Unplug the cables from the main PCB and unscrew the ground cables going to the different parts of the turntable.

Remove the following clamp diodes from the PCB

Phase 1

  • D705
  • D706

Phase 2

  • D735
  • D736

Phase 3

  • D765
  • D766

Schematic from the PDX-2000 (not the resistor value has already been changed in this version)

To identify the diodes there are silkscreen markings on the PCB denoting each component. The diodes are easily distinguishable as they are orange with a single yellow band denoting the direction of the diode.  Each pair of diodes helps with one phase of the DC motor. There are here to help with regulating the nearby op-amp but in our case they are hindering the motor under stress.

In addition to removing the diodes we also need to adjust the feedback resistor next to them. The original values were 820 ohm, they need to be adjusted to 470 ohm instead. 

Remove the following resistors and replace with 470r 1/4w (0.25w) (highlighted blue)

  • R709
  • R739
  • R769

Once soldered in and the leads clipped you can now re-instate the board and re-connect everything in reverse order.