Power for an LP 12

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Thanks Jeff,

For the link I will most certainly be checking this out. I knew of the Armageddon but always thought it to be as complex as the the Valhalla board.

If Naim can design a power supply for the LP 12 as simple as this why didn't Linn do something similar.

Can I ask one question, dose this circuit hold the motor / deck speed stable

Jay
 
Jeff,

You just know your NOT going to get an answer from Linn about this....

But thanks so much for a very simple answer & great link.

I know of an LP 12 really quite close to me (& silent as it's Valhalla recently died RIP ) thats going to be Gedded soon.

Jay
 
I knew of the Armageddon but always thought it to be as complex as the the Valhalla board.

There's NOTHING complex on the Armageddon. It's almost as simple as the LP12 BASIK PSU,
which the LP12 came with as standard (noth Valhalla and Lingo as an option).
This Basik PSU is basically the same as on any other turntable with an AC syncronous motor,
such as Rega, Thorens and some dozens more. It contains two resistors and two capacitors,
to decrease voltage and generate the phase shift.

Linn LP12 Basik:

16407926kr.jpg


an earlier one:

16407927iu.jpg


Not to forget, the former Linn entry-level table called "Linn Basik" (~1990) had a similar PSU.
 
Variations

I've found there's a lot of discussion on various sites about the 'geddon PSU. A few interesting ideas:

1- Tweak the running voltage of your motor to find the voltage that achieves minimum vibration. Some writers suggest removing the motor and holding it to feel the minimum vibration. Your test range could be 84 to 60 Volts. Some diy’ers say 72V is ideal, some 64V, others in-between. When you get your first approximation, fine tune the phase shift as well, to optimize entire “run” circuit, i.e., two voltages approximately equal, one 90 degrees shifted from the phase of the other. Adjust phase shift capacitor as needed, realizing correct value may be 0.18 uF – 0.22 uF. Use your scope if you have one to determine 90 degree point.

2- Add a varistor and/or an inline mains filter. (Not sure if either is needed).

3- Install a 10nF, 600v capacitor in series with a 100R, 0.5W resistor across each pole of the switch to eliminate switch on/off thumps.

I’ll build one for my TT when I can. Right now I’m too thick into studies (a return to grad school, retooling for a new career). :)
 
Hi All,
& thanks for all the info,

It's my understanding that the Armageddon had a large isolation transformer.
& thats what increases the cost.
Check this out..
*
pink fish media
DIY Geddon - LP12 power supply

all you need to know about Naim clone psu for LP12

Jay
 
Does anyone know If an LP 12 will run without its Valhalla / Hercules / Lingo power supply?
ie. just with a couple of capacitors ?

If so how is the speed maintained accurately ?

Jay

I thought I'd extend what others have said.

The LP12 motor has 4 wires - 2 grey, 1 red and 1 blue. The original LP12 PS was simply a series resistor to reduce (UK) mains voltage to around 110v, plus a 220nF cap to provide a phase difference.

IOW, you don't need a Valhalla / Lingo / Hercules / Armageddon to drive an LP12. But some of the above give you 45rpm, as well as 33.

The resistor (10K in my case, in Oz) goes in series with the 2 x grey wires and the cap goes between the blue and the red wires. The LP12 will sound pretty damn good with this basic PS - because the motor has great torque, because it's being fed direct from the mains ... not as an output from a sine-wave generator. However, the Lingo provides some supposed sophistication because (as well as giving 45rpm) it reduces the voltage getting to the motor, once it's up and spinning, which reduces the vibration generated in the motor.

And the speed is maintained by the mains frequency.

Regards,

Andy
Regards,

Andy
 
Much clearer now...

There are a couple of solutions then;

1, a cheep & cheerful version that uses just 3 or 4 components.

Tick Tock, could you post a diagram & component list for the circuit above please, or point me in the right direction please.

2, a much more expensive version of the same thing ie a proper Armageddon clone
that uses an isolation transformer + 3 or 4 components.

Hear; DIY Geddon - LP12 power supply - pink fish media

So wish id had a better look into the Naim version yrs ago.
hindsight is a, bitch......lol
A friend down in Oxford is trying to repair my Valhalla,
but for the future ill knock up at the very least the cheepy version.
When that is i get the use of my hand back.


Jay
 
IMHO the Armageddon (clone) isn't worth the effort (due to expensive transformer + chassis).

Just try Google. Be aware, some describe 50 Hz, some 60 Hz operation !!

All electronic PSUs give 50 Hz sinewaves for 33 rpm, requiring a "50 Hz motor". Older LP12 Basik
PSUs sold in the US came with a "60 Hz motor" (different pulley). I can't tell you quickly if there
are slight cap and resistor value variations.

60 Hz:

image.php


50 Hz:

Rega Motor Voltage ID Help

RegaMotorDriveSchematics1.jpg


RegaMotorlayout.jpg


again, Linn Basik PSU:

An externally hosted image should be here but it was not working when we last tested it.


However, if you have a Valhalla which needs repair, read this:

Valhalla repair and update... - pink fish media

I'd prefer both Valhalla, Lingo and Axis PSU over the Armageddon. The Axis does also work
on an LP12, but will need some tweaking to start the heavier LP12 platter. Similarly to the
Lingo it generates higher voltage at start and lower voltage some seconds later, but at a
lower level.
 
Last edited:
It's also said that the simple version is just as good as the expensive transformer Geddon.

The transformer is just providing some kind of filtering which can be done both cheaper
and more effective (EMI filter etc.).
If you have a suitable transformer and chassis on hand - go for it. Otherwise save your
hard earned money or get a used Valhalla/Axis PSU (the latter giving the 45 rpm option).

MI5 and CIA? Hope not. We already have the NSA watching us. :faint:
 
Ok what happened was this .
I decided that I wanted a 45 option for my LP12. So looked about for mods.

Found ones that weren't to difficult that many had used before. So a couple of Resistors some Caps & a new Crystal & hey presto it Worked, great. A real treat to hear some of my 12' 45s again.

However it seemed that maybe my soldering wasn't so good & the Valhalla may off flashed over cos it went pop big style. All the chips the rectifier & who knows what else, it was stuffed.

Nigel down in Oxford said he'd give it a go to try & fix it, its what he does.
10 out of 10 for perseverance, Nige.
It may yet still be salvaged.

So in light of not having anything to play music on, I thought i'd investigate alternative PSUs. The first thing to come up was the Geddon mod Simple But costly due to the Tranny.
Then the much cheeper & also fairly simple or "Basik" PSUs

That All seem (from what you guys are saying) to be better than the Much more complicated & expensive main PSUs.

What advantage these (expensive) ones have it seams, is that they do away with the need for an eco friendly finger push start, to get the plater spinning !
Oh & maybe a 45 option.

Am I grooving on the right track hear?

So to re-cap;
I would like to have as either back up or as a main PSU, for a UK 50Hz
LP12 motor;

A PSU that is,
First of all up to the job of spinning the plater.
If it needs a push start thats ok with me.

Second, that it Keeps the speed right.

Third, that its preferable simple & cheep to construct.
I'd rather pay more for a few good quality components, Than the same or more for lots ( ie complicated ) that didn't really do much of anything. & get hot or go POP

Jay
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.