Problems with Micromega stage 2 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th April 2015, 01:37 PM   #1
diyAudio Member
 
Join Date: Feb 2015
Default Problems with Micromega stage 2

Hello members, was wondering if anyone can advise re. problem with the above player. Been having problems of it not reading discs so purchased a new sled for it from Singapore CDM 12.4. Put it in recently and now playing all CD,s even CDR,s which it never did but the motor doesn,t stop when it comes to the end of the disc. It starts to rotate anti clockwise sometimes erratically but normally slowly. Any help appreciated. Mikeymoo
  Reply With Quote
Old 24th April 2015, 02:00 PM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Ah OK

I take it you mean the platter keeps rotating. That's odd... and it didn't do this with the old pickup ?

The only thing I can think of is that the RF is to high and the servo is 'keeping hold' of the disc. You need a scope to check the level on a standard CD (not a CDR). It should be around the 1.5 volt mark as a maximum.

I fitted a Japanese sourced CDM12.4 to my Stage 2 many years ago now and the RF was very high on that, around 1.7 volts or more from memory.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 24th April 2015, 02:12 PM   #3
diyAudio Member
 
Join Date: Feb 2015
Mooly, thanks for this but don,t have scope and probably wouldn,t know how to use one if I did. Could I use a multi meter to check this? Excuse ignorance on this but really are a novice. Stretched myself by changing sled as had to change all the wires due to the new ones being too short. Have cleaned it also as you advised once. It did rotate (CD) with the old pickup from memory but might have done the odd rotation anti clockwise I think. Thanks
  Reply With Quote
Old 24th April 2015, 02:44 PM   #4
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Its not really possible with a meter because you have no reference to work to and altering the laser power without knowing that means you could be increasing it beyond safe limits. You need to see the actual signal coming off the disc to know what is going on.

I'm trying to think back to when I had mine in regular service. If the signal from the disc isn't good or correct level wise then the servo makes a bit of a strange noise as it tries to let go.

I can't think of any easy way to do this. If the worst comes to the worst then mark the laser preset with a pen and turn it slightly one way and then the other (a few degrees, no more) and see if its better or worse. I shouldn't even be suggesting that because its really not the way to do it (its very unprofessional and courting disaster).

And I'm still trying to think back... is it to much signal that is causing this or to little... I'm not 100% sure thinking about it. Again... scope to see what is really going on.

The other big problem has been the quality of CDM12.4's offered for sale over the last few years. They have been out of production by Philips for a decade or so and the Chinese or wherever copies are very variable in quality.

Ultimately you need to get a scope on it to see
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 24th April 2015, 03:04 PM   #5
diyAudio Member
 
Join Date: Feb 2015
Mooly, is it possible for me to check the voltage with meter across the terminals of the spindle motor or the anywhere else? You could be right about the quality of CDM 12.4 as on close inspection it doesn,t look new but it plays CDR,s which the original never did. Cheers
  Reply With Quote
Old 24th April 2015, 05:18 PM   #6
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The spindle motor voltage wouldn't tell you much really because its under control from the servo. I'm afraid there is very little you can do without a scope, and even then a fix isn't guaranteed but it would show what the signal quality was like. The CD12.4 has the laser controlled via the chip on the pickup and so monitoring the current to adjust it up or down isn't an easy option either.

If its unusable as it is then tweaking the power up or down to observe the effect is an option. The problem is with the pickup so in some way there is nothing lost to try, as long as you accept the risks.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 24th April 2015, 06:03 PM   #7
diyAudio Member
 
Join Date: Feb 2015
Mooly, how could I tweak the power to the pickup? Is there any use in swapping any part(s) from the original? I,m keen to get it playing correctly as bit stretched to purchase new player and this did sound great. Thanks
  Reply With Quote
Old 24th April 2015, 06:23 PM   #8
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The power is adjusted with the tiny preset resistor mounted on the pickup itself. Its small and delicate but a jewellers screwdriver will fit. All you can do is move it a few degrees and observe. And as you'll see, you can't adjust while its playing. Turn the power off to move it. And mark the original position first and don't go more than a few degrees each way from that point.

There are no other adjustments at all on the Micromega.

There also has to be a big question mark over the pickup itself though and I know what you mean when you say it didn't look new. The last one I saw even smelled old, as if it had come from some old equipment. There were signs of the brown fur that old equipment gets too when you looked in the nooks and crannies of the pickup. The chassis and motors did look new though. That must be 6 or 7 years ago now.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 24th April 2015, 07:37 PM   #9
diyAudio Member
 
Join Date: Feb 2015
I tried it again and made a slight adjustment to the pickup. I presume it is a very small rotary switch on the back of the pickup itself facing backwards on a PCB??? Further more, the motor continues to spin anti clockwise when the draw is open with a slightly erratic motion like it is kind of pulsing. I put a circuit screwdriver on the chassis and it lite up. Is this odd?? Touching it I detect a minor vibration but didn,t get a shock. With the draw closed it also continues to rotate anti clockwise, like it never stops. Could it be something more fundamental like a switch not kicking in to turn the machine off? Thanks
  Reply With Quote
Old 25th April 2015, 07:01 AM   #10
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I think the Micromega has an earthed chassis so you should check that the mains lead is a three core and not a two and that there is continuity from earth on the mains plug to the metal chassis. You will have to measure to the metal screw inserts as the heavy anodising on the case acts as an insulator.

A neon lighting and feeling a vibration all point to a missing earth... which might have been done deliberately to stop a ground loop.

The motor moving with the tray open is very odd indeed. You mentioned earlier it might have done the same with the old pickup fitted. The only switches involved are a microswitch on the mechanism that detects when the pickup is at the rest position. If that were a problem then the sled motor would keep going and the gears would be making a racket and getting the teeth stripped. Only others are on the drawer to detect fully in and full out. On something of this age its possible there could be some electrolytics starting to deteriorate, particularly if its always powered up. Leakage from a small cap somewhere on the servo board is another possibility causing slight conduction between traces or components.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
micromega stage 2 fisha1987 Digital Source 4 16th March 2012 11:32 AM
micromega t-dac & t-drive problems saab Digital Line Level 0 13th November 2010 12:01 PM
Micromega Stage 2 (1?) ManUtd Digital Source 10 5th March 2006 07:22 PM
Micromega Duo CD3 Problems time Digital Source 3 23rd October 2005 07:50 AM


New To Site? Need Help?

All times are GMT. The time now is 10:45 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2