Repairing Linn Axis Motor Drive Amplifier

Anyone know how the pulley is attached to the motor shaft? I didn't see a setscrew.

Also, what does the curvature of the pulley do...keep the belt from jumping off during startup?

Thank you

AFAIK, most if not all Linn motor pulley is press fit to permanent. There's no setscrew. Removal may require the use of a hot air gun and very careful process to remove.
 
linn axis repair

Thank you for the capacitor list. Could you (or anyone who can be sure from the top photo ) possibly also specify the axial length, and radial diameter & lead spacing? I need to order the right parts from mouser.com (unless you have a better suggestion) for my technician, before he gets in there to see the actual sizes. A catch-22 I know. Would be GREATELY appreciated!
(2) 33uF 350V axial (250V ok)
(2) 47uF 250v axial
(2) 220uF 16V axial (long-lead radial will do if axial unavailable)
(7) 22uF 50V radial
 
Not too familiar with Linn, I’m more of an Ariston guy, but if I’m not mistaken, the curvature keeps the belt centered on the pulley.

Erie

I may be wrong, but I think the reason the pulley is shaped is so that at start up the belt drops on the pulley and is a mechanical way to increase torque during start up. It is also a means of adjusting the speed on the LP12. Neither I think is required on the Axis.
 
The Axis pulley is different compared to the LP12 pulley but I've read those that have replaced the axis motor with the LP12. The only thing that needs to be taken care of is the adjustment of the top plate so that the motor pulley and belt runs perfectly in the middle of the LP12 pulley. (This is adjusted with motor screws on the LP12, but with the Axis you adjust the top plate and the main bearing/inner plate instead of the motor. The final result is the same.)
 
Linn Axis PCAS011 power supply/driver for motor windings

The best online circuit description I have found is here.
Thank you very much for this URL.

In the moment I am looking for one or two PCAS011 board in faulty condition. I need this board for a friend, which have purchase an AXIS fragment without platter and this driver board as a spare part carrier.

He wants to use it to set up a test facility in order to be able to carry out comparative measurements for troubleshooting.

It should be not a board in working condition but a board, which needs a full restoration.

Thank you for offers under my email address as lollow:
kirschner-hifi (at) web.de

here an URL of interest:
Linn Axis Service Manual
 
Now I have got 5 AXIS boards in faulty condition. Additional I have found my own schematic drawing, create in the 90s, so as the genuine schematic from Linn - go to the attachment.
In my own schematic drawing, the values of the components are also entered (however, there could be drawing errors here), while Linn only entered the component numbering in the circuit diagram - i.e. without the component values.
Next time I will perform the repair of all boards, because I have two record player made for 60Hz AC line frequency (Moth Alamo/Kanoot,
Moth Kanoot / Rega / RB 300 tonearm w/ Grado ZT+ Cartridge with Audio Technica leveling feet Photo #2203459 - Canuck Audio Mart )
Maybe I can use it to raise the speed to the correct value.

Here the circuit description from pinkfishmedia under
Linn Axis PSU | pink fish media

So let's have a look at the schematic then. I'm no expert on this but if I offer a few thoughts someone more knowledgeable will probably be tempted to continue or correct.

Top left is the basic PSU function, 320v direct from mains and a simple 13.5v regulator.

Mid left are U1 & U2, D type flip flops. These get the logic gating to turn on and off, and to select 33/45 by holding switch on for longer period via the delay caused by components around C12.

Lower mid left, note that C14 and C15, though marked, seem to be missing as components! The 2 op-amps are acting as integrators with time constants dictated by the resistor networks around solid state switch elements U6-6,8,9 and U6-3,4,5. U3-5,6,7 is controlled by the 45rpm output of U2 and switches in this resistor network to make the change. This setup is the quadrature oscillator and produces 2 outputs at points O1 and O2, linked to the motor control section in the top right, which are hopefully exactly 90deg out of phase. Part way there! (Have a look here for better info, http://www.inesc-id.pt/ficheiros/publicacoes/2840.pdf.)

Top right is the motor drive itself. The out of phase signals from the previous section are amplified and fed to the motor windings. Each of the pairs U4-1,2,3/Q5 and U4-12,13,14/Q8 are switched off when the marked ON point is held low. When this is raised to about 13.5v by the U1/U2 gating, the 2 amplifiers are actived and O1 and O2 are transferred to the motor windings.

Below right is U5, again missing the components C18 and C20. Each of the first 3 amps is acting as a comparator and the very right is an integrator. The 2 right amps make up an oscillator through their control of the action of solid state switch U7-10,11,12. This affects the voltage on C19 which in turn affects the switching of the first comparator of the pair. Otherwise C19 will charge up and stop any switching action. The left 2 amps are set up to affect this action in 2 ways. If the OFF point is held high then the first comparator output is low and presumably C17 cannot charge up high enough under its link to the motor drive section enough to reverse this. If the switch U7-6,8,9 is open it will also be inactive. If these 2 allow it to be active then it will pass pulses to the next comparator based on the voltage across C17 which in turn reflects the current passing through the motor and R14.

There is a lot of interplay in which area is on at any time, and each area is obviously set up to trim the action of others. This will be the interesting area for discussion I think. Maybe a new Pink Fish Valhalla could come out of this?

Anyone want to comment on the bits I have not touched on or have wrong?
 

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Now I have got 5 AXIS boards in faulty condition. Additional I have found my own schematic drawing, create in the 90s, so as the genuine schematic from Linn - go to the attachment.
In my own schematic drawing, the values of the components are also entered (however, there could be drawing errors here), while Linn only entered the component numbering in the circuit diagram - i.e. without the component values.
Next time I will perform the repair of all boards, because I have two record player made for 60Hz AC line frequency (Moth Alamo/Kanoot,
Moth Kanoot / Rega / RB 300 tonearm w/ Grado ZT+ Cartridge with Audio Technica leveling feet Photo #2203459 - Canuck Audio Mart )
Maybe I can use it to raise the speed to the correct value.

Hello,

thanks for your post which is valuable to guide my own though regarding the motor regulation trouble I run into with my axis;

First problem appeared when sudden platter variation has occured in 33t prior stopping definitively.

So ,after reading the whole post upon the subject, I have checked the 320 v ..13.5 v and so on..including all the rectifiers status implemented on the circuit

Checking all the resistors values 2 times ,the drivers and power transistors..

After that I 've changed first part of the 8x electrolytic and back to a start 33t without any effects..

I 've changed both 33micro and 47 micro and the rest as advised ..

I start back to the 33t and the machine launch the platter with a greater torque effect during 8 to 10 second and stop /start again automatically with a buzz noise during the transistion..

The regulation problem is not fixed during the "so called" quiet period

I assume it is needed to pursue my investigations around the digital step...

According to your recommendations the tension value would drop from 75 v to 25v DC between the two DC power supply step upon the motor wiring?

Should you have any other suggestions...

Thanks again!

Raymond
 
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Hi Raymond,
I am not able to give you some advice because I don't understand this term:
1) "when sudden platter variation has occured in 33t"
In general I recommend to replace the IC's U1/U2 (4013) and IC's U6/U7 (4066) by sockets, because this IC's are very sensitive against overvoltage peaks from the mains (please note: there are no transformer and rectifier for the low voltage creating).
There are also often interrupts/transition resistances between the conductor tracks and the through-hole platings from PCB.

Comparison by a listening test between Linn's LINGO, homebrew clone of Dr. Fuß and Linn AXIS power supply - go to post 12 under
https://www.diyaudio.com/forums/ana...-description-sine-wave-osc-2.html#post6475049
 
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The circuit is designed to go into quiet mode which is around 25VAC but should only do that once the platter is up to stable speed. The circuit will only operate properly with the platter on. It should stay at the higher voltage until the platter is up to speed. I've attached a copy of the schematic in case you don't already have it.
The using of this motor control for other turntables/record players is possible without trouble, as long as 25VAC is enough for the used motor models (go to my listening test report mentioned in my previous post).

If in other turntable models is the same motor from the same time area at the same time than from Linn's AXIS and older LP-12 versions, is that guaranteed (resistor for speed and "Vpp" at output should be to replace by variable versions).

But what about newer motor versions with at first glance same specifications ? - go to
9904 111 31813 Series AC Synchronous Motors by Allied Motion

The question rises up, because with the old Philips/Airpax 110VAC versions (- go to first both attachment) it was really not to be expected that they would already run flawlessly between 18VAC and 25VAC with platter load from turntable.

Motors from attached images:
1) 9904 111 31302 MB02 (30 years old, VALVO/Philips Components)
2) 9904 111 31818 (20 years old, Airpax)
3) 9904 111 31813 (McLennan)/RS/Premotec
4) 9904 111 04802 (without brand naming)
5) original motor without brand naming for US-$ 299
Linn LP12 Motor – basilaudio.com
 

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Hi Raymond,
I am not able to give you some advice because I don't understand this term:
1) "when sudden platter variation has occured in 33t"
In general I recommend to replace the IC's U1/U2 (4013) and IC's U6/U7 (4066) by sockets, because this IC's are very sensitive against overvoltage peaks from the mains (please note: there are no transformer and rectifier for the low voltage creating).
There are also often interrupts/transition resistances between the conductor tracks and the through-hole platings from PCB.

Comparison by a listening test between Linn's LINGO, homebrew clone of Dr. Fuß and Linn AXIS power supply - go to post 12 under
https://www.diyaudio.com/forums/ana...-description-sine-wave-osc-2.html#post6475049

hello,

I am back on the subject and I got a vintage HAMEG 512 oscilloscope to get a visual analysis of the circuit board if needed.

So, I have an intermediate understanding of the circuit in regards of my own
knowledge level.

Please ,forget the term " when sudden platter variation has occured since it correspond to the beginning of the rotation problème i discovered

I have checked most of the component apart from all the chemical cap"s I replaced in following the first classic recommendation upon axis board circuit.

To date when I press 33rpm or 45 rpm button the "high torque" period of the platter launching last 7second but it stop after this step since "the low torque" does not follow due to a bad regulation I assume.


please could you advise for checking some critical point either to the IC digital stage or the symetric motor power supply (I also have the chips available if needed

Kind regards

Raymond
 
transistors equivalent to replace Q4 Q5 Q6 Q8 axis schematic

Hi,

I was in process to check the sine signal O1 and O2 that seemed correct at first sight in oscilloscope view with 90° in dephasage..

The problem to be analysed is the no regulation of the platter following high torque periode of 5 sec and stop with no low torque phase.(similar 33rpm or 45rpm)

Probably due to a lack of symetric current provided to each motor winding

Suddently a fusion of R1 and R12 R16 has occured...( perhaps I took to much time to test the circuit board without sub platter )

The following junction checking of the transistors is obvious!

Q4 Q5 Phm 501 ko...
Q6 Q8 Phm 8505 ko...

2X BC 184 ... ko

What would be the equivalent of Q4 Q5 Q6 Q8?

Any help would be appreciate to find the right replacement of these vintage transistors prior further investigations..

Kind regards

Raymond
 
there are various versions of this board. Some versions uses too small wattage for the resistors R17/16 (43K). For replacing use 2W version.
R23/6 is a usual low voltage version on the most boards. Creating high-voltage version is easy to realize. Use serial connection of 3 pcs. 270K or 430K+390K (several versions of this board was equipped in this kind).
BC184 = BC547 (T7/3)
For BUX85F (T4,5,6,8) I don't know exact replacement.

I use BUX84 or 2SC2501.
But please note: Outline is TO220 and no plastic version, i. e. not electrically isolated mounting base like
BUX85F pdf, BUX85F description, BUX85F datasheets, BUX85F view ::: ALLDATASHEET :::
and
https://www.nxp.com/docs/en/package-information/SOT186A.pdf
I use a MICA washer for TO220 - go to
W4605 KIT Winslow | Heatsink Transistor Mount Kit for use with TO-220 | 402-456 | RS Components
but due the high voltages this parts are better:
https://docs.rs-online.com/79b9/0900766b80e997ef.pdf
found on
Silfox : interface thermique, isolant électriques, conducteur thermique, Bergquist
The using of this motor control for other turntables/record players is possible without trouble, as long as 25VAC is enough for the used motor models (go to my listening test report mentioned in my previous post).

If in other turntable models is the same motor from the same time area at the same time than from Linn's AXIS and older LP-12 versions, is that guaranteed (resistor for speed and "Vpp" at output should be to replace by variable versions).

But what about newer motor versions with at first glance same specifications ? - go to
9904 111 31813 Series AC Synchronous Motors by Allied Motion

The question rises up, because with the old Philips/Airpax 110VAC versions (- go to first both attachment) it was really not to be expected that they would already run flawlessly between 18VAC and 25VAC with platter load from turntable.
no advice ?
 
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replacement BUX 85F by BX 85 in sandwich with mica

there are various versions of this board. Some versions uses too small wattage for the resistors R17/16 (43K). For replacing use 2W version.
R23/6 is a usual low voltage version on the most boards. Creating high-voltage version is easy to realize. Use serial connection of 3 pcs. 270K or 430K+390K (several versions of this board was equipped in this kind).
BC184 = BC547 (T7/3)
For BUX85F (T4,5,6,8) I don't know exact replacement.

I use BUX84 or 2SC2501.
But please note: Outline is TO220 and no plastic version, i. e. not electrically isolated mounting base like
BUX85F pdf, BUX85F description, BUX85F datasheets, BUX85F view ::: ALLDATASHEET :::
and
https://www.nxp.com/docs/en/package-information/SOT186A.pdf
I use a MICA washer for TO220 - go to
W4605 KIT Winslow | Heatsink Transistor Mount Kit for use with TO-220 | 402-456 | RS Components
but due the high voltages this parts are better:
https://docs.rs-online.com/79b9/0900766b80e997ef.pdf
found on
Silfox : interface thermique, isolant électriques, conducteur thermique, Bergquist

no advice ?

Thank you for your info

The situation to date as follow

further the fusion described in my previous of R1 (3w) R12 R16 and R14 I have replaced the transistors destroyed after checking the Junction

Q3 Q4 Q5 Q8 ko
Q6 Q7 ok (after second checking)

I got BX 84 to replace BX84F but It is needed to add mica isolator in sandwich since they are metal not plastic (collector on earth)

I set up mains and check usual 322 v and 13 v in power supply stage but no bright of the red or green 33/45rpm when i press start

The motor "growl" 5 to 7 second but does not turn

I put the scope on O1 & O2 that show the two sine wave 0.1 v (peak to peak ) in standby and 0.3 v (peak to peak ) when I press start and back to 0.1v after 5 to 7 sec

I put the multimeter on WO1+WO2 windings that display 20v

I put the multimeter on WO1+half point 10 v and WO2 10 V

I understand that the motor is not properly fed as a result

Please coud you tell me the additional point of checking either with the scope or the multimeter...

So ,i am wondering if the digital circuit is involved by the trouble since there is not any more lighting of the red and green led.. ( i have checked the two ones on multimeter ok)

I look forward to hearing from you soon

Kin regards

Raymond
 
Same problem here, but I did not realized (till I saw this post a minute ago) that the lower Voltage on the Motor down to 25V rms is a feature not a failure :) It is important to put the platter back and put the belt on. Than the motor will continue to run. If you put off the belt the motor stops after 7sec. The only Problem I have is that after switching to 45 the platter runs on 33 for a while and than stops. If you give the platter a push it goes on 45 and stays there... But that's so typical with British Hifi :p (and the older motors)

BTW I had an Resistor faulty in the motor power section. Should be 390K but was 1.5 meg. Also I de soldered the IC's and put in some sockets in. You now can change the IC's (there are 2 similar at least you can swap) to find the problem. And yes, I can remember the 4066 are tricky when faulty. Cheers, Oli
 
Hi, new member here,

I'm fixing up a Linn Axis from 1988 - usual problem of motor not starting or going backwards - and have recapped it although all the elkos measured fine with no elevated ESR.

However bias resistor R17 (43k) is burnt up though the associated transistors Q6 (BUX85F) and Q7 (BC184) seem to be ok.

I'm unable to find a 2W resistor to replace it - apart from the usual Chinesium - so is making up a series/parallel network out of 4 x 43K 0.5W metal film resistors an acceptable solution? The original parts list suggests a power rating for R16 and R17 of 0.25W which seems very low.

Thanks,

Simon
 

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...I'm unable to find a 2W resistor to replace it - apart from the usual Chinesium - so is making up a series/parallel network out of 4 x 43K 0.5W metal film resistors an acceptable solution?
Your proposed solution will look messy, but it's acceptable.
If the motor fails to rotate in the correct direction, there's a drive phase or motor winding failure. Check the motor windings for continuity.
R16 & R17 resistors do get hot during normal operation (motor running), but your picture shows a catastrophic failure. You'll need to find the fault!
The safest method of testing the circuit functionality is to remove the MAINS supply from the PCB and apply 12V DC (observe polarity) across C5 and check operation (12V DC PSUs are available on street corners ALL over The World). Old redundant modems/routers are a ready source of 12V DC PSUs.
If you're satisfied that the low voltage circuitry is fully-functional (observe the changes in LED intensity etc), energise the +320V rail with +12V - it won't turn the motor, but if you attempt to rotate the motor pulley in a counter-clockwise direction, you'll feel it kick back.

Good Luck!

P.S. Don't forget to replace resistor C19 (that's NOT a mistake - tantalum capacitors are the only resistors that I've seen decrease in value). Use a film capacitor.