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Older type of power supply
2018-07-19, 13:27
Post: #1
Older type of power supply
Hi everyone, this is my first post.

I've acquired an old 14xxx series table from circa 1974 with an SME 3009 S2 Improved arm and a V15 III cart, which sadly doesn't have a stylus, so for now its running with an AT95E. It has the original power supply, ie. before the Valhalla.

The turntable was original and unmolested which is what I was looking for. It has sat unused for around 25years and apart from a lot of grime, it's in very good condition. Because my system is vintage I'm not really interested in the upgrade paths and would just like to get it running to it's potential. (Yamaha CA610 amp and KEF Concerto/Richter Wizard Mk1s)

After giving it a service, adjusting the springs and doing a few other necessary tasks, it's now almost there. The belt was originally riding too high on the pulley, so I've adjusted that and it's now sitting at the middle of the bulge and running nice and quietly. The bearing is perfect, no platter wobble, no lateral play, and was well saturated in oil when I got it, so I was more than happy with that finding.

However, I checked the speed and it's running a little slow at 32.7 rpm, which was the nearest I could get it to 33.33 with the motor adjustment. Incidentally, I've done nothing to the motor and am wondering if I should take it out and check it? Is there anything that it would need doing to it that could help?

My question is whether replacing those 45yo caps would improve the speed, or is this about the best I can expect from the old girl in its original configuration?
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2018-07-19, 13:36
Post: #2
RE: Older type of power supply
(2018-07-19 13:27)oztayls Wrote:  Incidentally, I've done nothing to the motor and am wondering if I should take it out and check it? Is there anything that it would need doing to it that could help?

My question is whether replacing those 45yo caps would improve the speed, or is this about the best I can expect from the old girl in its original configuration?


As the owner of an original 1978 LP12, I would suggest a few drops of fine electric motor oil on the shaft under the pulley. I have done that every year for the last 40 and never had a problem with my original motor. Smile

Original 1978 Fluted Afromosia LP12, Ekos 2, Lyra Kleos SL and lots of other stuff from the 70's that still work fine.
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2018-07-19, 14:04
Post: #3
RE: Older type of power supply
Well done, it's nice to find somebody else wanting to keep the deck original
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2018-07-19, 14:29 (This post was last modified: 2018-07-19 14:32 by moomintroll.)
Post: #4
RE: Older type of power supply
Have you cleaned the motor drive pulley and the innerplatter where the belt runs?

Is it a new belt? An old belt may be to blame.

Have you replaced the suspension bushes with new ones, as they will have hardened with age? Similarly the four rubber feet.

Just because you wish to keep it vintage doesn’t mean it shouldn’t be maintained at spec.

BTW - from memory, the original power supply simply relied upon mains frequency to maintain speed. The capacitor will simply be to kick start the motor in the right direction.

‘troll
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2018-07-19, 17:24
Post: #5
RE: Older type of power supply
That's correct, the original power supply (later referred to as the basic power supply) has the motor speed governed by the AC line frequency as it is a synchronous motor. The circuit does indeed mainly make sure the motor spins in the right direction as otherwise you would have a 50/50 chance it would start up backwards. As LD100 mentioned a few drops of fine motor oil on the shaft of the motor from time to time. (I wouldn't think it would need it yearly but once in a while). If you can't get the speed correct by adjusting the tilt of the motor, and if the pulley and inner platter surfaces are clean, your most likely culprit is the belt. I have often seen an old belt where changes to motor tilt make little or no change to the speed. Replacing the belt brings the speed instantly closer to where it should be and responds better to slight changes in motor tilt allowing the speed to be set dead nuts on.

moomintroll's post is right on target, you wouldn't cringe at putting new tires on a 40 year old car. In addition to the rubber upper and lower grommets I would also prefer the new springs as they are more compliant, consistent and easier to work with. But if you want to keep it more stock the originals can certainly be made to work - it just takes a bit more time and effort.

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2018-07-19, 17:30
Post: #6
RE: Older type of power supply
Please see my signature. I believe mine is SN 14,254. Perhaps our decks were separated at birth.

Mine was original when I purchased it in 1990. It has been upgraded to the point of being a different deck. I do recall that it immediately sounded better than my Rega Planar 3 at the time. Therefore, the purchase.

So yours should sound really good if all is working properly.

LP12 (S/N 14xxx), Black ash plinth, Cirkus, Radikal, Kore, Ittok LVIII Mark 2, Krystal, Audiotech stand, Urika II, 530 system
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2018-07-19, 18:05 (This post was last modified: 2018-07-19 18:12 by Glyn Ruck.)
Post: #7
RE: Older type of power supply
The motor is not self starting because the magnetic field produced is not of the rotating type. In order to produce a rotating magnetic field there must be some phase difference. The capacitor is used to produce a phase shift of approx 90 deg. to make the motor self starting.

If the cap value has changed substantially with age it can have a negative effect on torque produced. I suggest a new cap of the same value & operating voltage.

Lubrication of the motor bushes is sensible.

A new belt is crucial.
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2018-07-19, 22:01
Post: #8
RE: Older type of power supply
Wow, I was not expecting such a great response. Excellent info guys.

I'm suspecting it is the belt. The table did come with a new belt in a packet, but it did seem quite old and stiff. I'm not even sure if its genuine or not. Out of interest, what is the correct length and width for an LP12 belt?

akamatsu, my table is #14778, so younger than yours, but not by much Smile

I'll crack on and lubricate the motor now. As I said, there are a few more tasks I have to do before I'm happy that I've done all that I can to get get her running in original spec. I'm certainly not averse to replacing what are considered to be consumables like rubber bits and springs so will order those as well. I think I'll leave those caps for now as its getting up to speed within 5-6 seconds or so, so they can't be too bad.

The other thing I have to look at today is investigate why the arm board is level with the deck on the LHS but below the level of the wooden plinth on the RHS. It's fine fore and aft. I took great pains to level the platter and the arm board seemed flat when I had it off the sub deck. This is not good as the arm rotates as it drops to the record making it difficult to get the azimuth right. I've read that the subdeck can warp from the heat of those spot welds, so that could well be a possibility as I did not check that.

On the plus side, it's coming up a treat in the looks department Smile

Once again, thank you all for chiming in with your thoughts and for sharing your experience.
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2018-07-19, 23:37
Post: #9
RE: Older type of power supply
Congrats on your new purchase.
Lots of great advice here.
I’m sure you have done a great job.
That said, nothing like taking the TT to a reputable dealer.
They will help you bring the most out of it Wink

86LP12 + 2015 Cirkus + Lingo2 + 2015 Standard Aluminum Sub-chassis/arm-board + Ittok LVII + 2017 Soundsmith rebuilt Troika + T-Kable + Tramp2 + Linto + Akurate CD + AV5103/AV5105 + 2X AV5125 + 2X Ninka + Trikan + 2X Komponent 104 + Sizmik10.25 + Silvers + Blacks + K400s + K20s
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2018-07-19, 23:44
Post: #10
RE: Older type of power supply
Do not expect the sharp 33.3 rpm when the accuracy very much depended on the noise AC mains. If it is feasible, whey crystal oscillator Valhalla and Lingo....etc. Big Grin
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