Early Meridian 508 CD Player. [Archive]

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JimC

03-02-2013, 11:28

Hi Folks,

I have been asked to look at a Meridian 508 CD Player which refuses to play (or even spin CD's).
The owner has approached Meridian who advised they could not help due to the age of the Player and the fact that the Laser is no longer available.

I have the Player apart and have done some checks. It has a Philips 'Swinging Arm' Laser assembly, I am unsure which one as yet, its Ribbon feeds a small RF PCB all still within the spaces of the Mechanism.

I have replaced the Electrolytics on this PCB (incidentaly all measured fine both on Capacitance and ESR) to no avail.

The PCB has a TDA 8808 RF Amp IC which seems to be working OK as I can get some semblance of Signal on its output pin 3 if I spin the Disc with my finger. This leads me to suspect the Laser and this PCB are working correctly and the fault lies later in the circuit.

Can anyone help me with a Circuit for this unit? Meridian, though pretty helpful did not have anything at thier Cambridge Office and advised to contact my Local Meridian Dealer who may have some information. I am still waiting a reply email from them (I initially phoned and they said they would forward any info via email).

Regards,

James.

P.S. Mods, if this is in the wrong place, I apologise and feel free to move the Post.

UV101

03-02-2013, 11:42

Sounds like its going to be based on a Philips.

Can you post some pictures please and I'll see if I can help ;)

Btw if its a swing arm laser, it'll be a CDM4 i suspect which was used in many players so very easy to find a potential donor. Having said that, it's usually a specific cap that causes read issues on this mech rather than the laser itself.

These pics are from my cd52 mods thread but may help identify the laser

http://i497.photobucket.com/albums/rr332/Trunky1812/CD52%20MKII/1d64d4e870264cfddfa0e21d31d8e426.jpg

This pic shows the ribbon from the laser

http://i497.photobucket.com/albums/rr332/Trunky1812/CD52%20MKII/c544a06775abf95d3c398b9ac9f5ba07.jpg

DSJR

03-02-2013, 12:56

Apologies if I'm confused more than usual, but wasn't the 508 a much later model way after the CDM4? Could be a CDM9 mini mech and as long as it's not the "engine" version, where the player manufacturer wrote the software, one might be able to find a replacement on fleabay.

I'm stunned that Meridian haven't kept spares though - they used to back in the day and the 500 series isn't THAT old........

JimC

03-02-2013, 14:44

Thanks for the replies folks.

I do think it's earlier than you both think but I could be mistaken.
I think it may be a CDM 2 Laser, I very much doubt it would be earlier than that but I won't know untill I get it fully apart and then I'll take some pics.

JC

DSJR

03-02-2013, 16:35

Bloomin' 'eck... Meridian must have stockpiled since I'm sure the 200 series was still around in the mid 90's?

The board on my CDM-1 was trashed and I couldn't sort it, so had to fork out for a good used one on fleabay. I transferred the board over, naughtily set the presets to approximately where the originals were, and am sorted for now. You may just have to try to find what other machines used the CDM-2 and locate one.

Philips are the pits where these things are concerned. As soon as they ceased production of mechs such as these, they all but wiped their hands of them as a supplier and offered no service backup at all, despite the fact that these better mechs and lasers last many decades with no trouble at all.....

JimC

03-02-2013, 18:22

It's just curiosity that'll have me dismantle the Mech to see what Laser is in there. As I said, I really don't think there's anything wrong with the Laser itself.
I have only once in 24 years that I have ever come across a failed Philips Laser of the CDM-0, CDM-1 or CDM-2 vintage.

I think the fault lies later in the Servo chain. Does anyone have any Service Info on this part of the circuit? Even perhaps from a later vintage player which may use similar circuitry even though with a Later Laser.

JC

UV101

04-02-2013, 21:55

Of all the CDM's thats the only one I've been unsuccessful trying to repair.
They used that mech in the 200 series before changing over to a CDM4 hybrid in the last models. I've gt 2 unwell 207 pro's with the CDM2 :(

On the 200 series, Meridian had their own servo control but it sounds like they changed an off the shelf later servo with the older mech in this model.

Something like a Marantz CD50 should have a similar servo to what you have there but with a CDM4. It might give some pointers.

Meridian used to be very helpful but I very much doubt you will be able to obtain a service manual now :(

The Black Adder

04-02-2013, 22:39

If it's anything like a Pioneer even the smallest bit of dirt on the lens can stop it even trying to read a disc, even a motor pulse.

Yomanze

04-02-2013, 23:56

EDIT: I mistook the picture of that CDM4/19 mech in the pic for the OP's transport. Swingarms are not so easy to replace, usually there is a suspect axial 33uf / 16v cap on the servo board that should be replaced, but unlike later mechs swingarms need to be 'dialled in' using servo / laser pots to get them working properly if you need to change the mech or laser, which requires a test CD & a scope. Are you sure it's a Swingarm? Did a bit of reading & the early 508s seemed to use CDM 12.4, which you can get from eBay for under £30 & should be plug & play.

Another edit: other records of it using CDM 12.3, either way, take a pic & might be in luck as both are easily available.

Yomanze

05-02-2013, 00:26

CDM 12.4:

http://www.maxdat.eu/_CD-Player-DAC-Transport-List/CDM12.4.jpg

CDM 12.3:

http://www.electronix.com/images/cdm12.3.jpg

JimC

05-02-2013, 07:46

Definately a Swinging Arm Laser.
I hope to get a chance to look at it again today at some point so will try and take some pics.

UV101, thanks for that, I'll see what IC's are in the Marantz CD50 and compare to what I've got.

I'm almost certain it isn't the Laser.

I've had this sort of fault caused by a missing clock to the final processing IC before the DAC's before. That's where the Spindle Drive signal is generated usually so may be a good place to start.

Cheers All,

JC

UV101

05-02-2013, 08:52

http://www.hifisounds.co.uk/ServiceManuals.html

Some of my manuals are hosted here, the CD50 (along with all marantz/philips of the same age!)uses a TDA8808 and 8809 with CDM4/19 which is a very common combination. You definately have a CDM2. I know Meridian changed the 207 pro during production from the 2 to the 4 but I've not actually managed to get a 4 working in place of the 2 even with service data. As I say, I've got 2 207 pro's which I just cannot get resolved. One of them I've actually changed the laser for another CDM2 but have the same issues. As you say, I suspect something in the servo area.

JimC

05-02-2013, 18:08

Hi UV101,

I didn't manage to get any pics today.

Thanks for the link though regarding the Manual for the CD50. I shall be able to use that hopefully to some success.

JC

JimC

06-02-2013, 18:51

Hi All,

firstly, apologies. It is indeed a CDM-4. I took it apart today and got some pictures, stupidly I have left these on my
works PC and I write this at home. I will supply tomorrow.

The unit has almost identical electronics to the CD-50 (thanks again for the link to the Manual UV101)
but on different PCB's, obviously.

So, I have been able to do some tests.

Firstly, at first applying Mains (the set remains in Standby) the laser though is activated, I presume to check for an allready
inserted Disc, and the Spindle Motor gives a little spin.
Nothing is read from the CD as there is no discernable Eye-Pattern visible on the HF out of the TDA8808.
If the set is then turned out of Standby and a Disc loaded the Laser is again lit but never is the Spindle Motor driven.

The idle signal on the MC (Motor Control) line is correct and I can see a change here when first Mains is applied and the Motor gives a little spin
but after that, when Play is pressed there is never any change.
I also noted no change at the input to the SAA7310GP on pin 42 (SWAB/SSM (''Start Spindle motor'')).
I noticed no discernable Signals on pins 37, 38 and 40 (Q Channel clock and data lines) but am not certain there should be
untill some Data is read as that is all to do with De-Emphasis.

Most all other pins on this IC are outputs. I have tried another SAA7310GP but the fault remains exactly the same.

The only other anomaly is some possible Data Corruption on the D1 to D4 signals between the SAA7310GP and its associated RAM IC.
On all other pins of the RAM chip the signals are all nice ''0's and 1's'' (0Volts DC to +5Volts DC) whereas on the aforementioned pins
(19 to 23 of the SAA7310GP) there is what looks like a little 'step' about 4/5ths of the way to +5Volts.
I thought I had one of these IC's to hand (it is different to the one used in the Marantz and I forget its number (I will get it when I
get the Pics) but alas no.

I wonder if anyone has a Marantz CD-50 and can scope and take pics of the traces on these pins so I can compare?

Cheers for now,

JC

UV101

06-02-2013, 22:23

Have you replaced ALL the elco's James?

There is a cap associated with the laser that always give issues on CDM4's but I cant remember the number in the CD50 manual. I'll have a look.

Also the CD52 I'm playing with in this thread has an identical transport and control. Only issue is my scope is packed along with most of my workshop for my impending house move ;(

** try the cap on TDA8808 pin 17 which is an electrolytic 22uF to gnd in the CD52 (part 2517) and 47uF in the CD50 (part 2521). Its the lasr supply.
Other than that, the circuits are identical. I seem to remember reading really low ESR caps here may cause a problem too so just try std elco's

Both manuals are on my site :)

*** just noticed you are local to me too! If you want to get together to have a look, I should have my workshop back running end of 1st week of March :)

JimC

07-02-2013, 08:05

Hi UV101,

all caps on the RF PCB replaced but I will check again the ones you are referring to, cheers.

All supplies are good and smooth even under load so I don't think it is that (could be wrong).

I will try and have another look today and I will remember to post the pics tonight!

All the best,

James.

P.S. I might try and feed the SP Motor from a DC supply, get the disc spinning when I press play, see if any info is read, that'd prove the rest of the circuitry was good.

JimC

07-02-2013, 17:27

I didn't get a chance to work on it today but here are the Pics as promised.

CDM-4 Top;

http://i1195.photobucket.com/albums/aa381/EL33SE/Meridian/PIC_0495_zps2e50fade.jpg

CDM-4 Bottom;

http://i1195.photobucket.com/albums/aa381/EL33SE/Meridian/PIC_0496_zps20997e62.jpg

Servo PCB;

http://i1195.photobucket.com/albums/aa381/EL33SE/Meridian/PIC_0494_zpse9d31970.jpg

RF PCB;

http://i1195.photobucket.com/albums/aa381/EL33SE/Meridian/PIC_0493_zpse0231fe2.jpg

From Bottom to Top; RF PCB, Servo PCB and DAC PCB;

http://i1195.photobucket.com/albums/aa381/EL33SE/Meridian/PIC_0492_zpsdb37477b.jpg

Cheers,

JC

JimC

12-02-2013, 17:48

OK, so curious-er and curious-er!!

Supplied the Spindle Motor from my Bench PSU and made to spin at roughly the right speed and pressed Play.
The Player read the Disc and started to play! I even got some Audio, mostly distorted but when just on the correct speed, undistorted audio!

Here's the odd bit. Plugged the Spindle Motor back into the circuit and..............all working!!!!!!!!!!!!!!!

What gives?!?!?!?!?

I'll see if it still is OK tomorrow.

JC

Yomanze

12-02-2013, 19:33

UV101

12-02-2013, 20:16

Result for sure!

Fingers crossed for tomorrow's test ;)

Firebottle

13-02-2013, 14:28

Connectors, or other things mechanical, pain in the *rse.

80-90% of faults come down to something mechanical :rolleyes:

:cool: Alan

JimC

13-02-2013, 17:53

Still working this morning.

Cleaned all internal connections, re-soldered any final suspect dry solder joints and gave the Laser Lens a final clean. Re-assembled and all still OK..........result, as someone has already said!

Listening to it now at home and all is well so far..................sounds..........ok.........st ill only on first disc though.
Very wide soundstage, lovely.
Further impressions to follow.

All the best folks,

James.

nat8808

27-02-2013, 05:49

Yeah!

The presumption that it's always the laser must have seen thousands of perfectly working, irreplacable lasers thrown away..

Well done for being more determined. Might go and find myself some broken players to fix..

UV101

16-03-2013, 19:18