Help Request: Meridian 508.20 Skipping - diyAudio
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Old 7th December 2008, 06:50 AM   #1
Stonker is offline Stonker  United States
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Unhappy Help Request: Meridian 508.20 Skipping

Hello,
I have a Meridian 508.20 CDP.
I am the second owner and ever since I bought the unit 3 years ago it has been intermittently skipping on playback. Pristine CDs generally are less prone to this.
I've finally decided to fix it.
I called Meridian USA and inquired about servicing this unit. The technician at Meridian I spoke with said more than likely the laser mechanism needs replacement . The mechanism is part CDM 12.4. They want WAY too much money for the mechanism and it is out of my budget.

I have a few questions:
1.) Iíve read a post which mentions the Ď508 20
transport having the wrong grease on the laser slide. This causes
a skipping problem on playback.í Can anyone speak to this or point me to additional info regarding this?

2.) Any suggestions about trouble shooting this and diagnosing the cause of the skipping?

3.) Does anyone know where I can purchase a functioning laser mechanism, CDM 12.4, for a reasonable price? Who makes the part is it Philips?


Thanks a bunch for any help with this.
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Old 7th December 2008, 08:20 AM   #2
poynton is offline poynton  United Kingdom
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Hi.

Have you 2 forum names ?


==========================

Philips make the CDM12.4.


It is available from many vendors worldwide although there are some "Chinese versions" which are not so good.

One of the common problems is hardenning of the grease.
Clean it all off carefully including the gears
Do not get any on the lens
DO NOT REGREASE !!!

Clean the lens with very dilute soapy water only


Andy
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Old 8th December 2008, 08:36 PM   #3
Stonker is offline Stonker  United States
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poynton,
Thanks for the info, it's very much appreciated.

It's not a bad idea to first open up the unit and try cleaning any possible grease as well as cleaning the lens before going forward and replacing any parts.

Regarding the replacement laser mechanism, I see several vendors on Ebay selling the CDM 12.4, a well as some parts store. Do you (or anyone) know of a reputable seller that stocks the genuine Philips part and not a knockoff?

Just how involved is it to swap out the laser mechanism on the Meridian? I haven't popped the case of the Meridian yet. Is it pretty much just a matter of correct order of disassembly with some delicacy?

Do you know where I would find info on disassembly? I am assuming it is a pretty tightly packed design.

Is any sort of adjustment necessary after installing a replacement laser mechanism to have it work and track correctly?

As a last resort, do you (or anyone else) know of a reputable technician who can replace the laser mechanism if I decide to pass on doing the repair myself?

Thanks a bunch for any input into this.


PS: regarding ID confusion, I had an issue posting but the moderator fixed my account.
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Old 8th December 2008, 10:53 PM   #4
robot is offline robot  Croatia
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I presume that you have service manual, because you gonna be in big trouble witihout it, if the laser isn t main problem. I m telling that becouse older versions of that cd player had a circuit connected with servo drive which includes kind a eprom chip (old quad had it, also) which is factory preprogrammed with unknown program, so I would consider that before I dissasemble the unit. The purpose of this chip is fine tuning of laser tracking unit, so malfunction of it could be a reason of track skipping (if the laser is working well).
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Old 9th December 2008, 03:53 AM   #5
poynton is offline poynton  United Kingdom
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Quote:
Originally posted by Stonker
poynton,
Thanks for the info, it's very much appreciated.

It's not a bad idea to first open up the unit and try cleaning any possible grease as well as cleaning the lens before going forward and replacing any parts.

Regarding the replacement laser mechanism, I see several vendors on Ebay selling the CDM 12.4, a well as some parts store. Do you (or anyone) know of a reputable seller that stocks the genuine Philips part and not a knockoff?

Just how involved is it to swap out the laser mechanism on the Meridian? I haven't popped the case of the Meridian yet. Is it pretty much just a matter of correct order of disassembly with some delicacy?

Do you know where I would find info on disassembly? I am assuming it is a pretty tightly packed design.

Is any sort of adjustment necessary after installing a replacement laser mechanism to have it work and track correctly?

Take a look at the CD67 manual. It uses the CDM12 mechanism so should give you some idea of the procedure. It is not difficult.

http://home.quicknet.nl/qn/prive/ra....E_doc_full.pdf



Quote:
As a last resort, do you (or anyone else) know of a reputable technician who can replace the laser mechanism if I decide to pass on doing the repair myself?
.........

Yes, his name is Brent (rowemeister on the forum) but he is in the UK !!!



Andy
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Old 9th December 2008, 07:45 AM   #6
Mooly is offline Mooly  United Kingdom
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Replacing a CM12.4 is very straightfoward. Does the mech look like the one in the manual Andy posted.
Any chance of a picture so we can see just what we are dealing with.
In any case assuming it's the Philips mech as in the manual, you have to remove it. Remove the tray first, by pulling it out and and then bending the plastic "catch" gently to one side to let it pop out completely. No timing worries with the gears etc. You then have to unplug any connectors carefully and very carefully disconnect the foil ribbon underneath. Don't pull it, the socket has a non removable captive clip that you need to push forward carefully to release it. It's easy ! Undo the 3 screws that secure the mech and remove completely.
If you are serious about having a go can describe in more detail what to do. The original pickup sounds like it does need servicing/degreasing, as this was a common problem. The CDM12s now available ( all the ones I have seen ) are not worth bothering with -- they are rubbish.
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Old 11th December 2008, 09:09 PM   #7
Stonker is offline Stonker  United States
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I DO NOT have the service manual.

Regarding cleaning the grease, what is the recommended solvent?
I called Meridian and they said that when the initial batches of the original Philips mechanism shipped, the grease was problematic. They received a replacement grease from Philips, but they have no clue what the lube is or how to get it. Their guess was that it was silicone based.

I will try to get some pics of my unit up, but Iím certain it is a standard Meridian 508.20. Assuming this unit has not been serviced, its serial number indicates it had the original CDM 12.4.

Mooly,
Regarding disassembly. Without popping open the Meridianís case I see no obvious manner of removing the CD tray. By merely extending the CD tray fully, from external inspection there are no visible clips. Yes, I m serious about having a go, so if you can provide more info Iím all eyes and ears.

What about the warning that Robot posted? Does anyone have any other info on this?

Finally, if all the CDM12.4ís available now are rubbish is there ANY reliable source for a quality mechanism without going through Meridian?

Is there a service manual online anywhere?
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Old 12th December 2008, 07:16 AM   #8
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To get at the mech open the draw by leaning the player forwards till it slides out and there should be some screws underneath the draw.
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Old 12th December 2008, 07:33 AM   #9
poynton is offline poynton  United Kingdom
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Quote:
Originally posted by Stonker
..................when the initial batches of the original Philips mechanism shipped, the grease was problematic. They received a replacement grease from Philips, but they have no clue what the lube is or how to get it. Their guess was that it was silicone based......................

The recommendation is to fully clean the mechanism including any gears and NOT to regrease with anything.

Andy
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Old 12th December 2008, 07:41 AM   #10
Mooly is offline Mooly  United Kingdom
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If the mech looks like this in Andy's manual ( and you are going to have to take the top off ) then you gently and slowly push the tray out by hand until it reaches it's end stop. Then see in the picture, left side "detail". Look down on the tray and you will see the clip stopping it coming all the way out. Push gently to one side ( it's only a bit of springy plastic ) and the tray will come all the way out. Thought it was on the other side of the tray from memory !! Whatever.
I have heard similar stories to Robots, the same tale was mentioned for Micromega (I own a Stage 2 -- same mech and pickup ), that they used proprietry software "in the CDM12.4".
Fact, the CDM12.4 is a standard unit, the electronics on the PCB underneath the pickup are just the RF amp and laser power control. Any special software/servo's are in the player, not the pickup.
Grease, erm, I use a special plastics/metal grease by Electrolube, will see if I can find a link to it. You have to remove the whole loader assembly and then the pick up from that. It really is straightfoward, nothing mechanical will self destruct.
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