Hello,
This is my first post here so please be kind.
I have minor dabbles into electronics but in no way skilled. I can solder.
My main system is Cyrus 2 and PSX (last version), Micromega Stage 1 and Tannoy Chatsworths.
The problem lies with the Micromega. After changing the drawer belt the transformer began to hum. I had a look to see any obvious culprits, caps diodes etc. but nothing obvious. The machine worked perfectly, drawer opening closing good and playing cd’s. even with the hum.
I took it to a local dealer who said he would take a look and while standing next to him we powered the machine up, with the cover off. As bad luck would have it, it decided to start popping the psu fuse. It obviously did not like travelling. I left it with him but he decided it was going to cost too much to repair with maybe possible the transformer and regulation circuit damaged.
I have decided to have a go myself but need advice please.
Is it worth me changing the components near the mains socket, caps, regs and diodes and giving it a go and hope the transformer is still good? Or could this be a way of wasting money? I will check the components on removal but feel they are probably worth renewing considering the age of the unit.
Or, if any one has a Stage player that could be used as parts?
Any help would be appreciated. Thanks
This is my first post here so please be kind.
I have minor dabbles into electronics but in no way skilled. I can solder.
My main system is Cyrus 2 and PSX (last version), Micromega Stage 1 and Tannoy Chatsworths.
The problem lies with the Micromega. After changing the drawer belt the transformer began to hum. I had a look to see any obvious culprits, caps diodes etc. but nothing obvious. The machine worked perfectly, drawer opening closing good and playing cd’s. even with the hum.
I took it to a local dealer who said he would take a look and while standing next to him we powered the machine up, with the cover off. As bad luck would have it, it decided to start popping the psu fuse. It obviously did not like travelling. I left it with him but he decided it was going to cost too much to repair with maybe possible the transformer and regulation circuit damaged.
I have decided to have a go myself but need advice please.
Is it worth me changing the components near the mains socket, caps, regs and diodes and giving it a go and hope the transformer is still good? Or could this be a way of wasting money? I will check the components on removal but feel they are probably worth renewing considering the age of the unit.
Or, if any one has a Stage player that could be used as parts?
Any help would be appreciated. Thanks
Hello mrbluesurf,
depending on your knowledge and skills in electronics, you could give it a try as the PSU in Micromega Stage 1 is fairly simple.
The fact that the transformer began humming and then popping the fuse might imply that you accidentally disturbed a component while replacing the belt, possibly creating a crack on PCB track or other damage. Humming usually means the increased load on transformer.
If you haven't already done that, test voltage regulators, caps and transformer with DMM.
I would start from there. There is no need to replace components without testing them first.
P.S. Kindness is mutually expected.
depending on your knowledge and skills in electronics, you could give it a try as the PSU in Micromega Stage 1 is fairly simple.
The fact that the transformer began humming and then popping the fuse might imply that you accidentally disturbed a component while replacing the belt, possibly creating a crack on PCB track or other damage. Humming usually means the increased load on transformer.
If you haven't already done that, test voltage regulators, caps and transformer with DMM.
I would start from there. There is no need to replace components without testing them first.
P.S. Kindness is mutually expected.
Thanks Willi
I Will start by checking like you suggest. Not sure on transformer though as it is self contained and seems to have many taps. Suppose I can check for shorts in windings.
Moral support is half the problem solved.
I Will start by checking like you suggest. Not sure on transformer though as it is self contained and seems to have many taps. Suppose I can check for shorts in windings.
Moral support is half the problem solved.
I would doubt the transformer is at fault... I used to use a Stage 2 player and I can't see how anything you could reasonably do replacing a belt would cause this.
Is the fuse blowing slowly ? or going with a bang ?
For faultfinding I would suggest you use a bulb tester (a 60 watt or even lower for this) mains filament bulb wired in series with the mains supply. That will save the fuse and give some protection against overcurrent.
The only "logical" thing you could possibly have done is to trap a wire from the PCB to the mechanism such that its touching the case and shorting a rail out.
Is the fuse blowing slowly ? or going with a bang ?
For faultfinding I would suggest you use a bulb tester (a 60 watt or even lower for this) mains filament bulb wired in series with the mains supply. That will save the fuse and give some protection against overcurrent.
The only "logical" thing you could possibly have done is to trap a wire from the PCB to the mechanism such that its touching the case and shorting a rail out.
Thanks for your reply Mooly,
The fuse is blowing slowly. I don't think it is a trapped wire as I did not have the board out at all.
Had a look inside and one of the IN1004 diodes has a small chip out of it, a resistor and small diode next to the V regulator looks like they have a shadow on the board, looks like they have been warm. Also the caps in the near area look ok but the cases look a bit blackened, I don't know if this is normal or not. I need to get them out and test.
Considering the age of the machine it may be worth changing them any way?
The fuse is blowing slowly. I don't think it is a trapped wire as I did not have the board out at all.
Had a look inside and one of the IN1004 diodes has a small chip out of it, a resistor and small diode next to the V regulator looks like they have a shadow on the board, looks like they have been warm. Also the caps in the near area look ok but the cases look a bit blackened, I don't know if this is normal or not. I need to get them out and test.
Considering the age of the machine it may be worth changing them any way?
Using a bulb will save the fuse and allow it to power up so that you can measure voltages. To blow the fuse suggests a "hard" fault and so it should be easy to determine which rail is the cause.
A "chipped" diode is not necessarily a problem... it happens in production. Its not detrimental. If one has failed then it should show even on an in circuit test.
If the machine worked OK up to the point of changing the belt then that suggests something has gone amiss somewhere rather than a genuine component failure. The only thing that comes to mind on that front is whether there is a problem with the tray switches... and its not detected a fully loaded state and so the loading motor has been powered all the time overheating and causing failure of the motor drive chip (L272's from memory). It all a bit tenuous but its the only thing I can of related to working on the drawer and assuming the player was OK before.
A "chipped" diode is not necessarily a problem... it happens in production. Its not detrimental. If one has failed then it should show even on an in circuit test.
If the machine worked OK up to the point of changing the belt then that suggests something has gone amiss somewhere rather than a genuine component failure. The only thing that comes to mind on that front is whether there is a problem with the tray switches... and its not detected a fully loaded state and so the loading motor has been powered all the time overheating and causing failure of the motor drive chip (L272's from memory). It all a bit tenuous but its the only thing I can of related to working on the drawer and assuming the player was OK before.
Thanks.
I was very lucky and found a Stage 1 on Ebay for £29 + post. Damaged facia and not reading disc.
I have taken the board out of the damaged one and put it in my payer with my drive and dac. Unfortunately it is an earlier board version but the whole unit is working perfectly again, although it was a bit jittery on a couple of cds but has played others perfectly with no grief. cds!!, give me vinyl any day.
I think I will e-mail Micromega to see if it possible to obtain another facia and I can get new laser on Ebay easily. In the meantime I think I may fire the damaged board with no load, i.e. no cd tray or dac connected or is this a bad idea? Then try light bulb, but not really knowing what I am doing test wise.
Maybe I overloaded the chip like you say pulling the drawer in and out when changing the belt, motor/ dynamo effect. It is a tda7073at chip. Don't know how to test it but will research.
Thanks again.
I was very lucky and found a Stage 1 on Ebay for £29 + post. Damaged facia and not reading disc.
I have taken the board out of the damaged one and put it in my payer with my drive and dac. Unfortunately it is an earlier board version but the whole unit is working perfectly again, although it was a bit jittery on a couple of cds but has played others perfectly with no grief. cds!!, give me vinyl any day.
I think I will e-mail Micromega to see if it possible to obtain another facia and I can get new laser on Ebay easily. In the meantime I think I may fire the damaged board with no load, i.e. no cd tray or dac connected or is this a bad idea? Then try light bulb, but not really knowing what I am doing test wise.
Maybe I overloaded the chip like you say pulling the drawer in and out when changing the belt, motor/ dynamo effect. It is a tda7073at chip. Don't know how to test it but will research.
Thanks again.
Sounds like a good result 🙂
I would look at fixing the old mech and laser rather than trying an ebay offering. The CDM12.4 has been out of production for a decade or more and the cheap (Chinese) offerings are generally of poor quality. You've only to look through these forums to see how many don't work or work poorly.
Post #2 here,
http://www.diyaudio.com/forums/digi...kipping-disc-reading-problem.html#post3016606
I would look at fixing the old mech and laser rather than trying an ebay offering. The CDM12.4 has been out of production for a decade or more and the cheap (Chinese) offerings are generally of poor quality. You've only to look through these forums to see how many don't work or work poorly.
Post #2 here,
http://www.diyaudio.com/forums/digi...kipping-disc-reading-problem.html#post3016606
Thanks for the links Mooly,
The drawer did eject and load and once or twice made an effort to read the disc so hopefully all it needs is a service. Got to get the later version board working as well. Will keep me busy.
The drawer did eject and load and once or twice made an effort to read the disc so hopefully all it needs is a service. Got to get the later version board working as well. Will keep me busy.
I have been trying to get the old laser up and running but having problems. Firstly I have degreased the drawer, sled and gears but not reading still. Looks like I have laser light and it does its little dance but the disc is not spinning up. Checked the motors with battery and the sled moves and disc motor spins ok. When I put my other mech in it works ok so the problem def lies with the second hand one.
After reading the links you sent I am considering total strip of mech and laser. As I do not want to damage anything I just want to make sure on how to get the blue gear and actual laser out of the sled etc. Does the gear just pull off and the worm just push out or is there some technique?
I think the problem may be the lens needs cleaning underneath. I am reluctant though to pull the diode out.
Do you think this is the correct approach or could it be a problem with the chip on the laser itself? I presume you can just move one mech to another machine and it work ok or am I mistaken?
Any advice would be appreciated....... or should I just drink tea instead?
Thanks
After reading the links you sent I am considering total strip of mech and laser. As I do not want to damage anything I just want to make sure on how to get the blue gear and actual laser out of the sled etc. Does the gear just pull off and the worm just push out or is there some technique?
I think the problem may be the lens needs cleaning underneath. I am reluctant though to pull the diode out.
Do you think this is the correct approach or could it be a problem with the chip on the laser itself? I presume you can just move one mech to another machine and it work ok or am I mistaken?
Any advice would be appreciated....... or should I just drink tea instead?
Thanks
The pickups and mechs can be swapped around. There is no alignment needed (or in fact possible on these). The gears essentially just pull off but if you look you will see a "claw" at the top of the gear shaft that holds the gear in a groove cut into the metal spindle. Just gently lever that away while pulling. The gears are very flexible. The worm gear doesn't really need pulling off the motor but the motor and gear can be released in a second by removing that metal clamp.
Cleaning the lens underneath can be done but its not something to casually recommend 😀
http://www.diyaudio.com/forums/digital-source/118902-stripdown-clean-cdm12-4-a.html
Cleaning the lens underneath can be done but its not something to casually recommend 😀
http://www.diyaudio.com/forums/digital-source/118902-stripdown-clean-cdm12-4-a.html
It looks like the transport is not getting through the initial procedure of reading a CD. The sequence begins with pickup moving to the innermost position and checking for an inserted CD by searching for a reflective surface at expected height - this is when the laser lights up and the focus moves up and down. When it finds sufficient reflection, the transport should spin up the CD to read out the TOC. There could be several reasons why the TOC reading sequence does not start but I would do some more testing before pulling the transport apart.
Thanks for the replies.
It just seems a bit odd that it works ok with one transport and not the other.
I will give it a full stripdown and clean before disassembly of lens unit.
I tested the motors with a rechargeable battery reading approx 1.3 v
What sort of speed would I expect to get off the disc motor and what amount of voltage does it normally run at? It did seem to run at a normal playing speed with a disc restng on top but didn't seem to have a lot of torque or rather it was a bit gentle starting up.
Thanks
It just seems a bit odd that it works ok with one transport and not the other.
I will give it a full stripdown and clean before disassembly of lens unit.
I tested the motors with a rechargeable battery reading approx 1.3 v
What sort of speed would I expect to get off the disc motor and what amount of voltage does it normally run at? It did seem to run at a normal playing speed with a disc restng on top but didn't seem to have a lot of torque or rather it was a bit gentle starting up.
Thanks
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That sounds pretty normal actually. I would have thought a volt or less in normal playback. The motors have very little torque, once up to speed they rely on the flywheel effect of the relatively weighty CD to smooth out small variations. The motor speed varies on playback as the disc is tracked from centre to edge (CLV or constant linear velocity) from around 500 RPM down to 200 or so at the disc edge. If there is doubt over the motor then a quick blast with a 9 volt battery each way can free up and clean up any deposits on the commutator.
When you power it up in the player, does the disc attempt to spin ? If it does then it suggests the player has at least found focus on the reflective surface. If it doesn't then its pointing toward a problem with the laser assembly itself.
When you power it up in the player, does the disc attempt to spin ? If it does then it suggests the player has at least found focus on the reflective surface. If it doesn't then its pointing toward a problem with the laser assembly itself.
No. The disc makes no attempt at all to spin.
It did spin up once after I had refitted it into the machine but a second attempt straight after failed and has made no attempt since.
It did spin up once after I had refitted it into the machine but a second attempt straight after failed and has made no attempt since.
That points to a problem with the pickup itself. By swapping mechs and it working you know that the rest of the player is OK. There's not much you can do beyond satisfying your own curiosity. You could dismantle the optics and give it all a good clean. Does the lens look shiny sparkly clean when viewed with a bright torch ? If you've resigned consigning the pickup to the bin there is nothing lost having a play. You could try tweaking the laser power to see if it made any different. Normally that's a big no no but when there's nothing to loose...
Also worth looking at the ribbon, particularly the ends and making sure it all looks OK.
Also worth looking at the ribbon, particularly the ends and making sure it all looks OK.
Lens has been cleaned and looks good under torch and magnifying glass
i have to strip it right back as i only clean gear in situ although it was moved around with battery power. If tweaking laser power is this done on laser mech or main board? I really don't want to touch main board as that may mess other laser mech and then I would be miffed truly.
i have to strip it right back as i only clean gear in situ although it was moved around with battery power. If tweaking laser power is this done on laser mech or main board? I really don't want to touch main board as that may mess other laser mech and then I would be miffed truly.
Laser power is by the tiny (and its really small) preset on the pickup PCB.
If you haven't stripped and cleaned the mech then are you sure the pickup is actually in the correct place at the disc centre. These pickups will never feel free and smooth to move, even with the sled motor removed. The important things are that there is no old hardened grease on the gears. Also check the micro switch near the spindle motor which is used to sense the position of the pickup. Make sure it looks OK and the leafs of the switch are not bent which would mean the pickup would not be in the correct place.
If you haven't stripped and cleaned the mech then are you sure the pickup is actually in the correct place at the disc centre. These pickups will never feel free and smooth to move, even with the sled motor removed. The important things are that there is no old hardened grease on the gears. Also check the micro switch near the spindle motor which is used to sense the position of the pickup. Make sure it looks OK and the leafs of the switch are not bent which would mean the pickup would not be in the correct place.
If the micro switch is positioned wrong this will affect the place where the laser stops I presume. I have cleaned and checked continuity and all is ok there. But I am wondering considering this machine had facia damages of the micro switch was displaced, although it looks ok, maybe adjusting mm at a time in direction may help?
I was also wondering about the nylon suspension as to me does not seem quite as central as the other mech. Maybe just by rotating them around?
I was also wondering about the nylon suspension as to me does not seem quite as central as the other mech. Maybe just by rotating them around?
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