Problem with Meridian 508.20 transport - diyAudio
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Old 29th August 2011, 03:57 PM   #1
sattwa is offline sattwa  Italy
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Default Problem with Meridian 508.20 transport

Hello everybody,
This is my first post here, but I keep reading your interesting and helping discussions.
I am having some troubles with my meridian 508.20 as it skips when the reproduction of the CD is at the middle (or at the end). The player has no problems at reading the CDs and CDRs (so I assume the laser is OK), it just skips when it reaches the middle of the CD.
I have read that this could be due to some grease that is sticking in the mechanism so I opened up the player and pull out the transport to clean it.
To be honest I did not find much to clean and the grease that I found on the gears did not look like it was hardened, but I might have not reached the right point to clean. Anyway the player continues to skip inspite of the little cleaning that I did.

What else do you think I could do?

Thank you

Fabrizio
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Old 29th August 2011, 07:08 PM   #2
Mooly is offline Mooly  United Kingdom
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It does sound like the transport is sticking.
What pickup/mech does this player use ?
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Old 29th August 2011, 08:19 PM   #3
sattwa is offline sattwa  Italy
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this is a picture a took of the transport
from another thread I read this shoupd be a Philips CDM 12.4
what is your thought?
thank you :-)

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Old 30th August 2011, 08:53 AM   #4
Mooly is offline Mooly  United Kingdom
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That is a CDM12.4

You need to turn the black worm gear by hand to move the pickup clear of the blue nylon gear.

Then remove the blue gear... it's a push fit with clips at the top, just be careful removing it. Wash the gear in alcohol etc and use paper/card to remove all grease from the teeth of the gear, also on the inner teeth. The original problem is the grease solidifying and getting hard "grains" in it that jam the gears.

Now examine the gear... they are very soft. Are there any burrs ? If there are and they catch then you have a problem.

Clean the worm gear in the same way.

The pickup should be "free" to move along it's track. Look at ALL the friction points on the pickup. Apply a tiny dab of grease here. Apply a dab to the metal rail. Make sure there is no hard grease in the gear "rack" on the pickup.

Use a plastics compatable grease to reassemble... this is critical and the viscosity is important. I always used this,
ELECTROLUBE|SPG35SL|SPECIAL PLASTICS GREASE, 35ML | CPC

Apply a light smear to the teeth of the gears.

That hopefully should resolve any playability issues.
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Old 30th August 2011, 01:59 PM   #5
sattwa is offline sattwa  Italy
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Hello Mooly thank you for your kind reply.
I have already checked and cleaned the blue and the black gears (using a needle), but I did it turning the black worm gear to see and clean all teeth (apart from those on the other side othe the blue gear). I wanted to remove the gears but did not know how to do it, I could not just pull the blue gear out.
why you say the gear is soft?
Difficult to judge the friction points where pickup slides. Turning the black gear by hand all seems to move freely but the little motor might not find it so easy.
Do you know if there is a way to tune the tracking? This could be another reason for the skipping issue..
Thanks.
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Old 30th August 2011, 03:18 PM   #6
Mooly is offline Mooly  United Kingdom
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The blue gear has integral "clips" molded into it. Just very gently prise them and the gear pulls straight off. The blue gear is often of a plyable soft nylon material rather than a hard plastic. You have to clean/check the teeth underneath that engage with the rack on the pickup.

The motor is held by a single metal clip. It's released from the top and just pushes back in to refit.

Friction points are where the pickup slides. In your photo its at the very top. The pickup slides along the plastic of the chassis. Look at both sides, top and bottom.

An old AVO8 meter on ohms x1 range put across the sled motor is sufficient to move the pickup slowly from end to end. I've never had a sled motor fail on these.
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Old 30th August 2011, 04:06 PM   #7
sattwa is offline sattwa  Italy
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I have seen the "integral clips" into the blue gear but It didn't seem so easy to press them all together to release the gear, I will have a better look. But my feeling is that the stucking grease, if any, is not there.
Also, the blue gear is hard.
I don't know if this can be of any help but the player usually skips when is at the middle of a CD (not at the beginning or at the end) and it always jumps back of few seconds and after the first time it has jumped it usually continues playing normally.
It sounds like a mechanical problem, but could it also be misalignment?
I also find this fine tuning of the player, I will try it, you never know..

http://www.hifi-advice.com/meridian-...menu-info.html

Ciao
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Old 30th August 2011, 06:04 PM   #8
sattwa is offline sattwa  Italy
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I tried that fine tuning but unfortunatelly didn't help.
So here again with the transport out.
Having a better look at the blue gear (and yes it is quite soft plastic) I think I should try to clean it better. But really I cannot see how to safelly take it out from that pivot. I even tried to bend those little clips with a little screw driver but I don't think this is the proper way.


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Old 30th August 2011, 07:12 PM   #9
Mooly is offline Mooly  United Kingdom
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Bending those clips is the proper way
It will come off easily... I have worked on many many of these.
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Old 30th August 2011, 07:46 PM   #10
sattwa is offline sattwa  Italy
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Quote:
Originally Posted by Mooly View Post
Bending those clips is the proper way
It will come off easily... I have worked on many many of these.
OK I will try again very patiently ..
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