Installation instructions

The following instructions are for the PS-X75 model, but they hold true also for the PS-X65.

1. Make sure the mains cable of your turntable is disconnected from the mains. NEVER work on the electronics while it remains connected to the mains.

2. Make sure that the internal power supply of the turntable is operating properly, i.e. delivers the correct voltage as described in the service manual and that the capacitors in the power supply are in good shape and perform their ripple filtering function properly. If not, then re-cap the power supply section before you go any further with micro replacement procedure.

Unsolder the original MB8841 from the mainboard of PS-X75 and remove the residue solder from the holes in the PCB where the chip was mounted

While you can solder the RCM directly in place of the original microcontroller, it is adviseable to install it in the way that will allow you to easily remove or replace it at a later time. As the RCM uses standard male goldpin connectors, you can use 2 standard female 21 pin headers for easy and secure installation of the RCM

Insert the RCM module into the socket observing the correct position of the module in the socket as shown in the photos below. This is critical as the module is not protected against reverse polarity and improper installation may result in damaged module

If the RCM is correctly installed, when you turn the PS-X75 on you should see 33 rpm indicator ligh up on the front panel of the turntable.

At this point all functions of the turntable should be restored and all buttons' functions should work. However before using the automatic start function you should perform the calibration steps as described further to ensure that the stylus drop point is adjusted to the right position on the record. Otherwise you are risking damage to your stylus if the arm is lowered outside of the record.

The PS-X75 uses optical method to detect and calculate the arm position (more precisely: the angle of the arm's deflecion in the horizontal plane) at any time during its operation. This detection method relies on a slotted encoder plate mounted on the arm's shaft. There are also two pairs of LED and a phototransistor. Through this arrangement not only can the microcontroller measure angle of arm's deflection by counting the slits, but also determine the direction of the arm's motion.

It may well be that in your particular case the encoder needs no adjustment, because your turntable had been operating properly with the original microcontroller until the micro failed. However in general case these turntables are old and chances are the encoder plate is misaligned. 

As you can imagine the optical slot-counting method can only provide the microcontroller with relative position of the arm, but for proper operation, it must know the arm's absolute position. This is achived by a clever arrangement of an additional cut-out in the encoder plate (that has the shape of an elongated triangle), an LED, a phototransistor, plus two potentiometers. The potentiometer RV103 is located on the main board and is only accessible when the bottom cover of the turntable is removed - i.e. only to a service person. This potentiometer is used for coarse adjustment of the stylus drop point. The other potentiometer is hidden in a hole under a rubber plug on the plinth next to the arm. It is accessible to the user and is used for fine adjustments of the drop point. 

The triangular cut-out in the encoder plate is used by the microcontroller to detect the reference position of the arm, from which all further calculations are performed based on the slit-counting. The potentiometers allow for adjustment of how far into the triangular cut-out will the phototransistor send signal to the microcontoller indicating that the reference position has been reached by the arm. 

Using the potentiometer in the plinth the user can adjust the drop point of the stylus on the lead-in groves area of the record. As the range of adjustment by either potentiometer is not very wide, it is extremly important that encoder plate is locked on the arm's shaft at the right position, so that the triangular cut-out lets the light beam through at the right moment. If it is not, it will not be possible to properly adjust the landing location no matter what the potentiometers' settings are. In practice it is quite tedious to adjust the position of the encoder and it is simply done by a trial-and-error.

The RCM software improves on the original Sony's control algorithms and provides for much easier calibration. Therefore it is not as sensitive to the alignment of the encoder plate, but none the less, requires the encoder plate to be roughly placed in a correct position.

The encoder plate is held in place on the arm's shaft by two hexagonal socket screws indicated by arrows in the photo below. 

Once we have the encoder plate secured in the correct position on the arm's shaft, it is also important to ensure that the slit-counting circuit is functioning properly. The adjustment procedure is described in p. 15 of Sony's service manual in the section "Slit A and B adjustment". The service manual is available from Vinylengine.com website. 

It it very important that this circuit functions flawlessly. It often happens that the RV101 and RV102 potentiometers fail due to aging. If you see erratic behaviour in arm positioning (e.g. from time to time, the arm misses the drop-point), you should consider replacing the these potentiometers with new ones.

It is also very important to ensure that the DC offset of the horizontal drive is brought to zero. In order to achive that, secure the arm in its rest position and press the Up/Down button to lower the elevator. The turntable will enter the arm balancing mode which you normally use to adjust the counterweight's position for the particular headshell/cartridge installed (this procedure is described in the Turntable's users' manual). But instead of adjusting the counterweight position you need to adjust the RV111 so that the voltage measured at the test point TP5 on the PCB is as close to zero mV as you can get it. 

The reason why this adjustment should be done with the turntable in arm balancing mode is that in this mode, the arm is guaranteed not to have any antiskating or driving force applied and thus its driving voltage (measurable at TP5) must be 0.

As indicated earlier on the main board there is a potentiometer designated RV103. Set it to its middle mechanical position.

Similarly set the user-accessible potentiometer located in the plinth's hole near the arm's base to its middle mechanical position.

1. Turn on the turntable

2. Put an LP record on the platter

3. Move the arm over the lead-in grove of the LP (make sure the platter is not rotating)

4. Lower the arm onto the record's lead-in grove using the elevator button 

5. When you are sure that the stylus is exactly where you want it to land during auto-start, press and hold the REPEAT button for 5-7 seconds until you hear a double beep from the RCM module . This means that the drop point position has been stored in the non-volatile memory of the RCM module. 

6. If the RCM emits a single long (3 sec) beep, that means that the calibration procedure cannot start due to some of the conditions not being met - e.g. the platter is rotating or the arm is not in its down position.

1. Turn OFF the turntable

2. Move the arm by hand so that the stylus is over the platter (anywhere, does not have to be precisely over the lead-in grove)

3. Hold down the START button and turn the power ON

4. You will head two beeps in rapid succession

5. The arm will move back towards the arm rest and the calibration calculations will be made in the process.

6. Once the arm has reached the arm rest and calculations have been finished you will hear the two beeps again.

7. If something went wrong you will hear a single long 2 seconds beep

This method works only if you use a standard hadshell, with overhang set as specified in the manual, and perfectly aligned its symmetry axis with the axis of the arm's headshell socket. In other words, if there are misalignments in the headshell socket this procedure may not give desired results. In such case please perform the manual calibration as described above.

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