Pav, John hasn't posted for almost two years. If you'd like your psu fixed stick it in the post and I'll repiar it for the cost of parts and return postage. I have a spare motor so all i need is the pcb and the switch. Pm me for my address.
Simon
Simon
Linn Motor Drive Amp repair
Hi all,
I am still alive😀 but have been busy with all sorts of things. Yes I can still fix Linn MDA assuming that is the problem.
John
Hi all,
I am still alive😀 but have been busy with all sorts of things. Yes I can still fix Linn MDA assuming that is the problem.
John
I'm wondering why the Axis uses the PS circuit shown above? Has anyone proved that it sounds better than the original (pre-Valhalla) LP12 "power supply" ... which was simply a 10K resistor in series (to lower the voltage which the gray motor wires see) plus a 220nF cap to provide a phase shift between the red & the blue motor wires?
The great thing about this original PS is that it provides plenty of drive to get the platter spinning. 🙂 (Much more than subsequent Linn AC PSes do.)
Regards,
Andy
The great thing about this original PS is that it provides plenty of drive to get the platter spinning. 🙂 (Much more than subsequent Linn AC PSes do.)
Regards,
Andy
Andy,
Some other topics cover this question, as far as I remember some people
have tried Axis PSUs in LP12 and they found it superior to both the basic
PSU and Valhalla. The Axis is similarly silent to the Lingo.
However, as always, personal taste will vary.
Admittetly, the Axis is designed for the lighter Axis platter. When driving
the heavy LP12 platter it suffers from it's low torque and will require some
help by hand to start.
Thanks, Holger. It seems to me that is one advantage of the basic (original!) LP12 PSU - great torque because it comes straight from the mains! 😀
But, of course, it's only 33rpm.
Regards,
Andy
changed caps - still weird
My Axis II / Akito bought in 1990 had periodically speed drops.
Thus, I changed all electrolytics, thereby upgrading all 22µ/50V to 22µ/63V and all 220µ/16V to 220µ/25V. Unfortunately, I couldn't get a higher voltage replacement for the 250V and the 350V types fitting on the PCB, so I used the original values.
The axis is assembled again but still suffers from sudden speed drops lasting some seconds from time to time. Furthermore, the red LED now is slightly glowing when the axis is switched off. When the axis is running at 33 rpm, the red LED is bright and stable. When switching to 45 rpm, the green LED toggles between a bright state and a slightly darker state every 6-7 seconds. I can not check if the speed is stable at 45, as I have no suitable record - only LPs.
If I'm right, the red LED is connected to the outputs of the U1 and U2 FlipFlop and both outputs are high when the Axis is switched off. When switching on, the U1 becomes low and current is flowing from U2 to U1 via D5 (red) and R30. A glowing LED means that both outputs have a different voltage or that a leakage current flows from U5 via the SD connection.
Has anybody an idea how to fix it?
My Axis II / Akito bought in 1990 had periodically speed drops.
Thus, I changed all electrolytics, thereby upgrading all 22µ/50V to 22µ/63V and all 220µ/16V to 220µ/25V. Unfortunately, I couldn't get a higher voltage replacement for the 250V and the 350V types fitting on the PCB, so I used the original values.
The axis is assembled again but still suffers from sudden speed drops lasting some seconds from time to time. Furthermore, the red LED now is slightly glowing when the axis is switched off. When the axis is running at 33 rpm, the red LED is bright and stable. When switching to 45 rpm, the green LED toggles between a bright state and a slightly darker state every 6-7 seconds. I can not check if the speed is stable at 45, as I have no suitable record - only LPs.
If I'm right, the red LED is connected to the outputs of the U1 and U2 FlipFlop and both outputs are high when the Axis is switched off. When switching on, the U1 becomes low and current is flowing from U2 to U1 via D5 (red) and R30. A glowing LED means that both outputs have a different voltage or that a leakage current flows from U5 via the SD connection.
Has anybody an idea how to fix it?
I got it: C17 and R44 had no ground connection. Seems that I have damaged the via under one pin of C17.
The Axis is up and working again.
Several years ago I had repaired 20 AXIS controller boards, but all of them had total failure.
Now I have such an AXIS speed controller PCB include the motor itself, but this time also with speed fluctuations than your device (first time and therefore new for me).
In opposite to your observations I note also fluctuations in brightness of the LED's for displaying the speed. This and also the speed fluctuations is to observe both at 33 RpM (red LED) and 45 RpM (green LED).
Voltage variations I observe at follow devices/connections/crossovers:
R29 (430K)/D9
D8/D9/PIN14, U5
PIN12, U5/C19 (2µ2 tantal)/D14/R56
I have replace this tantal capacitor against a foil type from WIMA (MKS) without success and without any changes.
Follow questions rises up:
How operates the speed control of this unit ?
The current sensor resistor R14 (10Ω) goes goes beyond the switch from IC7 (PIN8/9) to C17/PIN5/IC5 (begin of the loop for speed control).
The end of the loop must actually be PIN7 of U4, which goes to the control PIN number 6 of the switch from IC7 (PIN8/9).
But what makes the integrator U5 (PIN1/2/3) ?
Next step, which I will try, is connect an other motor part to rule out the motor as source of the observed and unwanted large wow and flutter.
Maybe there are experts here, who know this unwanted effect and the reasons therefore - thank you very much.
Have you checked C17? It seems to be important to the feedback control and if it is dry and out if range, the board behaves like described.
I'd change this before anything else.
I'd change this before anything else.
Can anyone tell me what the two small potentiometers on the Axis PSU do? I am wondering if they are for speed adjustment.
They are for speed adjustment. Just be sure to adjust the one for 33rpm first, as the other one builds on top of this one.
The motor was the reason for the mentioned trouble.
Nevertheless I want to have a detailled circuit description, because I am not a good circuit analyst.
Thank you for posting this when you did. I recently had my Axis fail, much to my dismay, and thought I may have to abandon it, after almost 27 years of service (it was a wedding present to me from my wife!). The information on your post led me to replace (the visibly defective R1 resistor) and the electrolytic caps mentioned. The table now spins as new. I have a total investment of $1.73 in parts, plus some hours on my bench, which I log as education. Question: should I consider upgrading those replaced components, and if so, with what?
If you replaced them with good quality electrical equivalents there should be no need to do anything further at this time.
The electrolytic caps do tend to go because of the heat of the board. Still mine lasted almost 15 years plugged in before the caps failed. The heat eventually dries out the electrolytic caps. Our Linn service technician in Western Canada advised replacing the electrolytic caps with tantalums and that they would probably never require replacing again.
Are the required values available as tantals? I doubt tantals are more reliable
compared to current 105/125° lytics. At least older tantals (used in old Linn
gear) tend to suffer from leakage. I'd bet Panasonic FR will do the job for the
next 20 years.
compared to current 105/125° lytics. At least older tantals (used in old Linn
gear) tend to suffer from leakage. I'd bet Panasonic FR will do the job for the
next 20 years.
The electrolytic caps that tend to go are the smaller values in the low voltage circuitry. There's 4 x 22uF and 1 x 2.2uF, 25V rating are adequate. These are readily available. You can certainly find high quality electrolytic caps these days that would do the job too. I changed mine about 10 years ago now. It was a pretty cheap fix.