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Rega P3 experiments

davidsrsb

pfm Member
I have been fixing up my second hand early P3, 240 V motor
Playing the Elipson tests record, the 3150 Hz track measure 3200 Hz, so a little fast

I recorded that track and a bit of processing in LTSpice detects the wow and flutter to be mainly 0.55 Hz at only 0.05%, remarkably good.

Looks like I need a mains synthesiser
 
People seem to have noticed that the new Rega belts (EBLT) run slightly slower than the older ones so that might be cheaper than a mains synthesizer.
 
People seem to have noticed that the new Rega belts (EBLT) run slightly slower than the older ones so that might be cheaper than a mains synthesizer.

Maybe the new belts are mostly on decks with the newer power-supply.. ?
I have trouble understanding how a belt alone can make a deck slower,
and if it would it appears to me it must have a certain amount of slip / less traction ?
 
People seem to have noticed that the new Rega belts (EBLT) run slightly slower than the older ones so that might be cheaper than a mains synthesizer.
I am an electronic engineer so the synthesizer is a challenge.
Getting a Rega belt in Malaysia is not so easy

Not that the speed worries me so much, I dont have perfect pitch. Low wow and flutter is far more important
 
Testing with HFS75 today and the 3 kHz track measures as 2999 Hz, W&F still excellent
Now I am wondering what my mains is up to
 
As one record is about 1.5% fast and the other spot on is it worth checking one directly after the other to see it it is one of the records that is 'out'? As you say though it could be the mains frequency and stability is much more important that absolute speed.
I couldn't understand how one belt can be slower than another, but if a softer more compliant belt is used, it stretches slightly more on the tension side so is effectively longer that the harder belt and therefore runs slower, everything else being equal.
 
^ This.

The Rega pulleys have flat sided V-shaped belt paths, wherein, a fatter round cross-section belt will run very slightly faster, vs. a thinner cross-section belt will run very slightly slower.

Rega have always been very OC when it comes to their belts, however, some variance must exist, especially so, between different suppliers over many decades. What should be patently obvious to even the casual observer is that the mains frequency will vary the speed by more than will any good belt.

Regardless, an interesting experiment with the old style motor suspension is to align the motor such that the belt is too taught and notice the speed change. Same with aligning the motor such that it leans in toward the drive hub leaving the belt too loose. Guess which setting is faster?

 
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When I had my early (240v planar 3) it was about 3% fast all the time
I made a double pulley (before you could just buy them:rolleyes:) and got the speed spot on
It was of course more by luck than judgement...just taking it off and machining another thou' off it ...bit by bit
 
When I had my early (240v planar 3) it was about 3% fast all the time
I made a double pulley (before you could just buy them:rolleyes:) and got the speed spot on
It was of course more by luck than judgement...just taking it off and machining another thou' off it ...bit by bit
Just out of curiosity, did you try putting a fresh Rega sourced belt on first?

Also, if by 'early', you meant one with the O-ring suspended motor, was the pulley well centred within the plinth hole whilst under belt tension?
 
Yes I tried a new belt ( in fact two in the end)

I replaced the motor mount rubbers with new...and it was as centered as my OCD could get it:D
 
Testing with HFS75 today and the 3 kHz track measures as 2999 Hz, W&F still excellent
Now I am wondering what my mains is up to

I always thought that the electricity companies could vary the mains frequency, depending to some extent on loading, but as long as they get the correct average over 24 hours then everyone's digital clocks would keep good time.
 
I always thought that the electricity companies could vary the mains frequency, depending to some extent on loading, but as long as they get the correct average over 24 hours then everyone's digital clocks would keep good time.
Accurate over months not 24 hours and a maximum error of over 30 seconds
https://gridradar.net/en/net-time
The European grid manages about +/- 0.1 Hz
https://gridradar.net/en/mains-frequency

Malaysia does not publish details, but will be much worse as it is a small and only national grid. Size gives stability
 
I replaced the original motor in my Planar 3 with the upgraded 240V motor with fixed mounting. I found it quite an improvement.
 
Do you mean the phasing capacitor? This can affect torque and vibration, but should not change the speed
Well, one could say that the speed has changed when the platter starts rotating in the wrong direction. :D

IME, a faulty cap can affect speed when the phase angle varies enough to cause vibration. More often than not, this will be an old Rifa PME271 series cap that has long since seen its hard candy outer shell become cracked. These should be replaced, whether they still work or no.

Also, if one is going to be changing the old capacitor out, the original 15KOhm resistor was prone to failure and may as well be changed out for a metal oxide type (higher temperature tolerance) of 12KOhm (UK) or 10KOhm (rest of Europe).

Alternatively, what with Rega motor upgrades having come available since circa 2000, one could pickup an earlier two capacitors board (usually with motor attached*) that has been cast aside by someone who has gone old (110V) or new (24V) motor upgrade kit.

Rega Planar early resistor capacitor PCB [image credit: member custom_made of stereonet.com]:
post-144521-0-17584300-1393914839_thumb.jpg


Rega Planar early two capacitors PCB [image credit: @Seanm]:
40600078564_924371bcdc_z.jpg


* Having the motor included can be an advantage, as there were motor orientation variations early on that can have the motor wires too short to reach the later PCB terminals.
 
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