Origin Live Building a turntable almost from scratch - Manual (Page 19)

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Please note that very occasionally the bearing house will not be truly vertical due to slight variations of the thread pickup
on the nuts. It is purely a matter of trial and error to get this right by rotating the nuts and bearing house slightly. Aim to
get the platter parrallel with the arm-board in at least the plane that affects cartridge “azimuth”. For definition of
“azimuth” see section on “hi-Fi Cartridges – setting up procedures”. You can always alter the height of the arm to get
the other plane true.
Be careful in moving or transporting the deck - it is possible to bend the spring supporting bolts if a severe side
movement occurs (bear in mind that the sub-chassis etc. is quite heavy). Ideally it is best to use the transit bolts to hold
the sub-chassis rigidly to the plinth topboard when transporting the deck. In the unlikely event of a sub-chassis foul on a
support rod, the answer is usually to bend the bolt to the correct position. Only resort to such measures after you have
checked all other possibilities such as springs not locating in their sub-chassis housings etc.
Set up of motor and power supply
In the first 4 hours of use from starting up the motor, the speed tends to drift but then settles down permanently. To
burn in the regulator board components we recommend at least 4 hours of running the motor before you accurately set
the speed.
If you look under the deck in the area of the switch you will see a PCB screwed in a position such that you can adjust the
motor speed using the two rectangular blue trimmers
Connect up the motor & transformer
VERY IMPORTANT – if the leads are not correctly connected you can burn out your motor – For this reason follow
the procedure outlined as follows –
The thin output wires from the power supply are only 12 volts maximum and therefore safe to handle. Voltages inside
the transformer are dangerous so the transformer case should not be unscrewed or opened.
First connect the plug on the flying lead from the MOTOR to the CONNECTORS emerging from the regulator board
under the plinth (if not already done so) The connections push together – excess wire can be pushed, tapped or tie
wrapped out of the way so that they do not foul the sub-chassis assembly.
Now connect the lead from the in line TRANSFORMER (power supply) to the DC connector socket at the back of the
turntable. It is useful to screw lock this connector.
Plug in the power supply to the electrical mains supply – allow 10 minutes or so for circuits to warm up before carrying
out any speed checks.
When the rotary switch is turned fully anti-clockwise the motor is off. One click of the switch clockwise is 33.3 rpm and
the second click clockwise is 45rpm. Use the strobe card provided to set the speed of your deck. Speed should only be
checked with the cartridge dragging on a centre track of a record. It will take 4 hours for your dc regulator board to run
in before you can set the speed accurately without “drift”.
Setting the motor
The motor speed is set by 2 rectangular blue trimmer resistors. Access to these trimmers is possible from the underside
of the deck (this is most easily achieved by getting the front left hand corner of the deck to overhang an edge of furniture
or similar. You must let the board components “run in”- we recommend 4 hours for this. The reason is that the motor
speed changes significantly while components burn in but they “settle” after 1 to 4 hours. This is best carried out with
the motors running fast so turn the pre-sets clockwise as outlined below.
When the rotary switch is turned fully anti-clockwise the motor is off. One click of the switch clockwise is 33.3 rpm and
the second click clockwise is 45rpm.
Now adjust the motor speed as follows using the 25 turn resistors P1 and P2 on the regulator board (P1 is the blue
component nearest the centre of the printed circuit board and P2 is the other blue component situated nearer the end of
the board). Note:- to increase speed turn the presets clockwise using a small screwdriver in the top slot. The pre-set
screw will not fall out and may need a fair number of turns to set the correct speed so keep turning until the speed
changes. If the screw reaches the end of it’s travel you can usually hear a faint clicking sound for a complete turn.
With the switch set at the 1 st click - set P1 so that the platter turns at 33.3rpm . Use the strobe disc provided to set the
speed (full instructions are on the card). However if you have problems using the strobe card, then count the rpm using
the following method. Counting the 33.3 revs per minute is best accomplished by placing a small piece of sticky tape on
the perimeter of the platter and then counting 100 revolutions. 33.3 rpm is exactly 100 revolutions completed in 3
minutes. To save time in the early stages it is easiest to count 50 revs in 1 minute 30 seconds (or 25 revs in 45 seconds)
and save the 100 count for the final check. When setting the speed, place the arm on the centre track of a record so that
the cartridge is tracking the grooves this ensures that the drag of the cartridge is taken into account (even though the
difference is only 0.8 % from setting the speed without the cartridge on the record). Speed variations of up to plus or