Hi I have an old Micromega Microdrive transport that has a drive motor / laser mechanism based on the CDM9. The transport powers up and the laser seeks but the CD does not spin. I've checked the motor continuity is good and that the resistance varies as I rotate the motor. I've also checked the supply voltage from the PCB to the motor and this reads 3.39V. Looking on the side of the motor it says 5.9V - in fact it is pretty much like the motor that is linked to here:
http://www.partmate.com/download/OPU/CDM9.pdf
from the old thread between Lgrau and tiefbassuebertr
http://www.diyaudio.com/forums/parts/31564-datasheet-cdm9-cdm9-pro.html
My question is, is the likely reason why the motor does not spin that the supply voltage is too low? I do not have a bench supply (may buy one) to test the motor operation.
I've got basic electronics skills, can use a multimeter/soldering iron but don't have any schematics for the Microdrive so have no idea how to trace the power rail for the motor. Can anyone offer any suggestions / pointers - these would be most gratefully received. I loved my old micro system from Micromega, after I got the pre-amp/DAC fixed a few years back, the transport stopped working and I was gutted. It would be great to get it running again.
Thanks in advance for any pointers.
--
--Dinan
http://www.partmate.com/download/OPU/CDM9.pdf
from the old thread between Lgrau and tiefbassuebertr
http://www.diyaudio.com/forums/parts/31564-datasheet-cdm9-cdm9-pro.html
My question is, is the likely reason why the motor does not spin that the supply voltage is too low? I do not have a bench supply (may buy one) to test the motor operation.
I've got basic electronics skills, can use a multimeter/soldering iron but don't have any schematics for the Microdrive so have no idea how to trace the power rail for the motor. Can anyone offer any suggestions / pointers - these would be most gratefully received. I loved my old micro system from Micromega, after I got the pre-amp/DAC fixed a few years back, the transport stopped working and I was gutted. It would be great to get it running again.
Thanks in advance for any pointers.
--
--Dinan
The ostensibly very nice, brushless platter motor of the 9pro mech is actually a whole lot less reliable than the brush motors used on the lower 9 models. Sometimes they get hopelessly flakey, probably due to bad hall sensors, but most common fault is failure of lubrication in the shaft bearing. It is possible to disassemble, clean & relubricate this motor, but it should not be attempted by anyone that doesn't have a lot of experience with such things.
@stephensank Thanks - I've ordered a second hand CDM9 motor/laser mechanism. I'll give this a try. I do wonder though if it is something in the supply voltage for the drive motor 3.39V seems low - I know it is a DC motor but would you expect it to spin with this voltage applied? I think I need a bench supply to test it.
If anyone has schematics for the Microdrive I'd be very grateful.
Thanks again. 🙂
If anyone has schematics for the Microdrive I'd be very grateful.
Thanks again. 🙂
The brush type motors should go into orbit with 3 volts. If its not spinning on that its faulty. Are you sure you are measuring across the motor to confirm the voltage and not from ground ?
So an update - its working!
What did I do:
1) reseat the ribbon data cable from the laser assembly in the socket in the main PCB.
2) take the power plug from the motor apart - strip the leads and reassemble the plug before plugging back into the main PCB.
3) raise the height of the CD platter on the drive motor - using two jeweller's screw drivers to carefully prise the platter up a few millimeters.
The motor would now start spinning fine and the disk would rotate but I was getting errs in reading. I found two more issues:
1) I had to tweak the height of the platter until it stopped getting read errors.
2) The data cable to the laser was somehow being fouled and stopping the laser arm moving freely. I carefully moved the power cable to the drive motor and ensured that the arm moved freely before screwing the motor assembly back into the transport.
I suspect the original problem was someone had pressed too hard down on the CD platter clamp and/or the motor had seized up a bit through lack of use.
Thanks for all the help/pointers - I now have a working transport!
Unfortunately now my Micromega Variodac seems to have lost one channel - that will probably require a signal generator and an oscilloscope to debug, neither of which I have...
Perhaps time to pay for an expert. It is the last part of my Micromega microdrive-variodac-microamp that is not working so would be great to sort it!
Thanks again all! 🙂
What did I do:
1) reseat the ribbon data cable from the laser assembly in the socket in the main PCB.
2) take the power plug from the motor apart - strip the leads and reassemble the plug before plugging back into the main PCB.
3) raise the height of the CD platter on the drive motor - using two jeweller's screw drivers to carefully prise the platter up a few millimeters.
The motor would now start spinning fine and the disk would rotate but I was getting errs in reading. I found two more issues:
1) I had to tweak the height of the platter until it stopped getting read errors.
2) The data cable to the laser was somehow being fouled and stopping the laser arm moving freely. I carefully moved the power cable to the drive motor and ensured that the arm moved freely before screwing the motor assembly back into the transport.
I suspect the original problem was someone had pressed too hard down on the CD platter clamp and/or the motor had seized up a bit through lack of use.
Thanks for all the help/pointers - I now have a working transport!
Unfortunately now my Micromega Variodac seems to have lost one channel - that will probably require a signal generator and an oscilloscope to debug, neither of which I have...
Perhaps time to pay for an expert. It is the last part of my Micromega microdrive-variodac-microamp that is not working so would be great to sort it!Thanks again all! 🙂
Could well be the platter that was fouling. There should be a blob of epoxy "in the hole" that acts as an end stop.
The Micromega... if you mean one channel missing on the analogue outputs then that might be fairly easily fixable. Check the basics, supplies on opamps, trace the signal from sockets back to the output opamp etc.
The Micromega... if you mean one channel missing on the analogue outputs then that might be fairly easily fixable. Check the basics, supplies on opamps, trace the signal from sockets back to the output opamp etc.
- Status
- Not open for further replies.