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Old 26th August 2013, 10:36 AM   #21
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You are absolutely correct Nigel, switching to the 4.433 MHz crystal frequency does drop the voltage to the motor. My experimenting and measuring showed only 65 volts hence the need to also change resistor R13 to around 15k to bring it back up to 85 volts. The motor will run at the lower voltage but will not start without a push.
My simple ( primitive) version works surprisingly well but I can see from your input that I should really make the phase cap switchable from 22 to 11 to further help smooth the motor. In spite of this however the motor in the AR seems just as quiet and smooth with the 'wrong' cap value but further tweaking can only improve things.
Cheers
Graham.
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Old 26th August 2013, 10:51 AM   #22
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The extra 0.22 uF was about right .

I do hope I get the valve design to work . I will post it as a soldering design as it is simple enough to draw . I did my Valhalla diagram backwards as the 4020 ripple counter connects that side as seen from above .
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Old 26th August 2013, 02:14 PM   #23
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Click the image to open in full size.


As I thought an ECC81 ( using ECC85 as that is all I have , similar ) will not drive the motor directly . 30V rms is not bad ( 10 : 1 probe ) . The motor in 4K64 without the inductance . It is a genuine LP 12 motor from the old Belgium factory ( my spare one ) .

Motor is rotating albeit zero torque . If I make an external phase shift device I will try the direct coupled version ( hence 4K7 load as it is very like the motor static load ) . The distortion is OK and good a basis for feedback ( 14 % THD ) . Anode plates are not glowing red . 0.2 uF phase shift ( all I have to hand ) .
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Old 27th August 2013, 07:20 AM   #24
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Click the image to open in full size.

Considering the simplicity of this oscillator it is giving excellent performance . 0.25 % THD . The capacitors are 5% chosen at random . The purple resistor should be 318 K approximately for 50 Hz and I guess 910 K paralleled for 45 Hz . Notice an allpass filter does give a sine and cosine wave as proven by the maths ( 1.414 times larger ) . By combining the 180 degree section via 91K and 10 K a distortion null is created giving 4.1 Vms at 0.07 % THD . This would improve if 1N4148 was used in place of red LED's with reduced output . TL074 used as op amp . LED's are OK on temperature stability considering the cost , IN4148 perhaps less so . An ice cream put on the LED's took output to 4.21 from 4.1 V (null ) .

If I didn't make an error the DC residual is too great for direct coupling . A lovely powerful feel to the motor without sustained rotation using SVF oscillator . Output was 60 Vrms for 5 V input using ECC85 at 10 mA per phase .
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Old 27th August 2013, 01:59 PM   #25
Jay1234 is offline Jay1234  United Kingdom
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Ok its still a bit to technical for me, but if you can say exactly what components I need to get & where to put them, do I need to remove any existing components or cut into the board at all ?
Will the switch be the same as the Linn or does that need to be replaced or a second one added?

If it is supposedly so easy & cheep to do this why didn't Linn do it in the first place....or is that a very stupid question
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Old 27th August 2013, 06:02 PM   #26
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How I did it was to use 12 V to switch the 2 relays . In fact being you are UK also I used the switch on the mains socket to switch ( cheap and simple ) .

I am a little concerned you attempt this as it is a bit dangerous . Live anywhere near Oxford ?

Why didn't Linn do this ? Simply because it was not done in house . The crystal is not exact so maybe an idea they didn't want to follow ? Lingo isn't the one to copy . If people don't get bored I will try to perfect a Lingo for them . I am 80% there and got 63 Vrms from 2 x EL 84 today . The oscillator is fine . I am looking at a cathode follower now .

You need .
3.276mhz Hc 49/u Crystal

4.433619Mhz 30ppm HC 49US Low Profile Crystal

220nf 275v Class X2 Capacitor

2A SPCO Subminiature signal relays

HF7FD0121ZSTF 12VDC 12A SPDT Miniature Cube Power Relay

AC/DC Unreg Ptop Psu 12v DC 500ma
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Old 27th August 2013, 06:46 PM   #27
Jay1234 is offline Jay1234  United Kingdom
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Thanks for that Nigel, as I understand it as long as the Caps are fully discharged (20 min?) It should be safe to tinker with?
I don't have much understanding of electronics but I can make just about anything, & have made valve amps, was a long time ago though!

So with this list of parts (all from the same source makes life so much easier) is it a case of swapping components, or is it a new bit of circuit thats being created?
& or where do they go ?
What & how is the AC/DC Psu used for?

You mentioned a Lingo are you building a DIY version? praps it might be better to wait till you get this sorted.
Are you proposing a kit or circuit diagram with list of parts? how would the circuit board be sourced.
sorry for all the questions.
Jay
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Old 27th August 2013, 08:33 PM   #28
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Nigel, I have an old Axis PSU. Any idea to increase voltages to make
it powerful enough to start the heavier LP12 platter?


Quote:
Originally Posted by Jay1234 View Post
I don't have much understanding of electronics but I can make just about anything, & have made valve amps, was a long time ago though!
Jay, to be honest, if you really aren't experienced in electronics,
keep your hands off a Valhalla with voltages exceeding 300 V.

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Last edited by ticktock; 27th August 2013 at 08:36 PM.
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Old 28th August 2013, 08:52 AM   #29
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The Axis was a weird turntable . So well engineered and yet was very hard to sell . The PCB very complex and seemingly well thought out .

The motor I think was the slightly cheaper version often talked about on on Forums ( RS sell it at about £40 ) .

Looking at this thread the 15 K might be it or the 3 K resistors . Maybe get the circuit from this guy ? It looks possible .

Linn Axis PCAS011 power supply

Jay if I can find my Valhalla I will play with R3 ( ? additional relay and resistor or relay section ) . The idea is to put a meter in the red or blue phase . The voltage required should compensate for the inductance at 67.5 Hz ( AC current range ) . This is more critical than people realize . 75 Hz I suspect is the resonance point of the Airpax motor ( Philips Belgium , it has had many names ) . That is OK as we want 67.5 for 45 RPM . I had the motor working nicely at 5Hz by mistake . Common sense says use the highest speed you can . I would say 130 V at 75 Hz are the upper limits . 130 V 50 Hz might give too much vibration even on ideal waves . On very sick phase correct waves at 63 V vibration was excellent ( 20 % THD ? ) . If I fitted a 78 pulley at about 32 mm if there is room ( 75 Hz ) . I guess 32 Hz for 33 1/3 and 43.3 for 45 . Almost suggests 45 rpm at 50 Hz would not be bad ( 27 mm ) . That would 86.7 Hz 78 which might be OK . 33 1/3 at 37 Hz . In my bones I feel you might win more than you loose at 37 Hz . That would still be 133.2 poles per platter rotation compared with 180 standard ( {250/ 33.33} 24 , 250RPM = 50 Hz ) .
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Old 28th August 2013, 09:50 AM   #30
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Quick question for you Nigel. Over the weekend I intend to further refine my 'el cheapo' version of 2 speed Valhalla by adding the alternative motor phasing cap.
Can you tell me did you calculate the value of 0.11 for 45 rpm or experiment, or a lucky dip in your parts drawer ???
Cheers
Graham.
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