REGA Planar 3 restoration

The iconic Rega Planar 3 turntable has been around since introduction in 1977.  The most recent editions are the P3 or RP3.

Thus, there are 30 to 40 year old Rega Planar turntables now in need of restoration.

This Planar 3 is from early-1980s, fitted with a Linn LV-V tonearm (and an un-branded Japanese moving magnet cartridge).

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This example has an attractive Cherry wood trimmed plinth.

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This early serial number indicates late 1970s to early 1980s manufacture.

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P2030352

(Seen in this example above, Planar 3 turntables from 1977 to 1983 were usually fitted with the Rega R200 tonearm, manufactured by Acos.)

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This cartridge is unknown brand, labelled “Japan”, moving magnet type with spherical stylus.

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Although these AC motors are theoretically locked on mains freq, we found that the condition of the phase split cap can have an effect on motor speed – maybe to do with the variation in uF with age, affecting secondary winding phase delay and motor torque and smoothness, causing slightly slower speed.

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(Underside, motor cover removed.)

 

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The original capacitor case is cracked.  The voltage dropping resistor dissipates 1.5 to 2 watts and gets hot, but is still in good condition – however a good idea to maintain some air clearance off the PCB.

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Capacitance has increased +50% with age, damage.

 

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Premotec/Airpax motor circuit (R1 = 12k ohms for this 230vac version).

On these PSC (permanent split cap) motors, ideally for minimum motor vibration:

  1. The 2 ‘phases’ (each winding) should be nicely balanced – ie. receive the same voltage.
  2. The ‘phase difference’ created by the capacitor between the 2 windings should be 90 deg.
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(On another Rega Planar 3, measuring the motor running voltages.)

With this 35 year old Planar 3 however:

  • Measured platter speed at startup was around 33.8 rpm, decreasing to 31.5 rpm (after 30 mins) and increasing again 33.1 rpm after 1 hour.
  • Measured AC voltages after 30 mins are A = 67.5v, B = 81v, C (between windings) = 54.3v.

A and B windings are not balanced (to help minimise vibration) and not within the 90-110 recommended supply volts.

Secondly, using triangle trig maths, we can calculate that the phase angle between A and B windings is presently around 43 degrees – not close to the ideal 90 degrees.

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(The platter main bearing nut needed tightening a little.)

New capacitors fitted – the original 0.22uF cap has been replaced with 2 paralleled 0.1uF, 300vac MKP Class X2 caps = 0.2uF.

With slightly lower capacitance than stock, volts balance between windings is much improved and phase delay is not increased significantly (ends up around 102-105 deg).

Importantly, winding volts balance and phase shift are much better:

A=99.4v, B=98v, C=157v.
Thus, phase delay between A and B windings is ~105 deg – MUCH better than before & close to ideal 90 deg.

(Using the original drive belt, a new Rega ‘upgrade’ white belt to be fitted.)

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The stainless steel bearing shaft (8mm) looks in excellent condition,  no wear marks (as should be expected with a brass bushing)

The ball is there, however the oil well is almost dry.

We will clean out and re-install with 3-4 drops of SAE 80 ‘hypoid gear oil’ as recommended by Rega (I believe).

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The new Rega ‘upgrade’ white belt, replaces the original – which is softer and has stretched slightly.

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New belt fitted.

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Final motor speed is a steady 33.8 rpm – slightly fast (~2%), which seems to be typical of Rega Planars.

Note:

If you wish to get the volts between windings more perfectly in balance, Premotec (McLennan) suggest inserting a trimming resistor/s, as below:

Premotec-bal

 

Listening test:

(After re-setting cartridge alignment, tracking force (1.8g), VTA (level), anti-skating…. )

Rega Planar 3s sound excellent to me, dynamic, ‘open’ and musical.

Bass is quite extended, but treble lacks some ‘sparkle’ due to the spherical stylus of course and image ‘focus’,’ depth’ could be better.

(The Lounge Audio LCR (Mk I) phono stage used below, offers good bass power, nice tonal warmth, ‘scale’ and ‘harmonic decay’.  LCR EQ seems to allow the music to ‘breathe’ in the bass and midrange especially.  Inductors provide a ‘low impedance’ path in the lower frequency ranges.)

 

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One thought on “REGA Planar 3 restoration

  1. Pingback: Bargain bin – Rega RB202 tonearm | D a r k L a n t e r n

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