On the pickup, both used the TDA1302T, but a different spindle motor and worm gear motor. They also had ribbon cables that were different (though same size, shape, etc.) The pickup I received in the mail was used and had some dried grease in the gears, so I simply switched out the laser assembly.
I got a little frustrated with the thing and started some speaker projects that I should finish this week. (I'm restoring some Snell J IIIs and Klipsch Heresys.) As soon as I get my workspace clean again, I'll take some photos of what I got and will probably ask you all for some more help scoping it...I'm close to taking it to my tech who will charge an arm and a leg, but will give it one last go for the sake of knowledge if nothing else.
The original CDM12.4 pickup and mech with the "soft flexible" blue nylon gear doesn't seem to work when used with the harder white nylon type gear. The backlash is different and the pickup has trouble reading the TOC's constantly scanning the disc for many seconds. Sometimes it will then play other times not. A strange issue but one I have encountered a couple of times.
Mooly,
Good to know, but I actually kept the blue nylon gear. I haven't opened up the transport in a few days, but I'd like to check the alignment of its gears with the teeth of those on the "new" laser. That may be a problem too...The company may have also just sent me a faulty laser, but I'd like to assume the best and think it just has some compatibility issue.
The gears have no special alignment, it's just a gear train driving the sled.
Another common issue are burrs in the soft nylon gear teeth on the inner part of the shaft. The pickup is never particularly smooth when you move it by hand (with the worm gear and motor popped out) but should run slowly from end to end with a 1.5 volt battery across the motor. Actually you need a low value resistor in series with the battery to get it as slow as possible and it should still make it end to end at whatever the slowest speed is you can get away with. An AVO 8 meter on low ohms range will just power the sled when placed across the motor.
Another common issue are burrs in the soft nylon gear teeth on the inner part of the shaft. The pickup is never particularly smooth when you move it by hand (with the worm gear and motor popped out) but should run slowly from end to end with a 1.5 volt battery across the motor. Actually you need a low value resistor in series with the battery to get it as slow as possible and it should still make it end to end at whatever the slowest speed is you can get away with. An AVO 8 meter on low ohms range will just power the sled when placed across the motor.
Finally finished those speakers and am back to the Meridian. The "new" laser didn't work and so I put the old one back in. Seems like the reading issue is worse. I didn't check the caps, but the values are no too common and didn't have any replacements on hand so I wanted to try to properly scope it to see if the laser is still at fault.
I'm attaching a photo of the chip and surroundings. Mooly, I followed your schematic a few weeks ago when we started this chat. I didn't get anything like the images you attached, but didn't feel like I could get a good ground and trace around that capacitor. After seeing the chip itself, do you have any recommendations?
Attachments
at best you order the CDR765 mentioned about post #20.
You will find presently one device in used and working condition by ebay - go to
Philips CDR765 CD CD Recorder | eBay
Then you can replace crossover both the complete mechanism and the laser heads only and you will see, what happens (please note, the laser head you need is in use only in the replay-section and not in the recorder section).
This means, you have good conditions for your troubleshooting.
Without a second cd player unit for checking the optical pick up/mechanism stuff it is very difficult to obtain a clear statement concerning the right error-causing device.
You will find presently one device in used and working condition by ebay - go to
Philips CDR765 CD CD Recorder | eBay
Then you can replace crossover both the complete mechanism and the laser heads only and you will see, what happens (please note, the laser head you need is in use only in the replay-section and not in the recorder section).
This means, you have good conditions for your troubleshooting.
Without a second cd player unit for checking the optical pick up/mechanism stuff it is very difficult to obtain a clear statement concerning the right error-causing device.
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Thanks, Mooly. Like I mentioned I don't know much about using the scope (and mine is very simple), but I did try the spots you mentioned and got a fairly good wave. Seemed when it skipped, the wave lost focus...I feel like I'm letting down the folks that contributed to this chat, but I'm going to have to take it to a pro. There is a tech near me who owned his own high end shop and repaired the gear he carried. He has done some nice work for me in the past and I hope he can get it going. I'll let you all know what he says. If he can't fix it, you all may hear from me again.
FM
FM
Hope you get it sorted 
Another thought if you are interested in narrowing down the problem is to monitor the DC voltage across the sled motor as a disc is playing. The voltage is normally very low as the motor is "shuffled" along. If you watch the worm gear while playing a CD it almost trembles to and fro advancing a few degrees at a time. If the sled is sticking the voltage will suddenly start to rise until there is enough force to overcome the friction and the sled jolts forward and which you hear as it jumping.
Another thought if you are interested in narrowing down the problem is to monitor the DC voltage across the sled motor as a disc is playing. The voltage is normally very low as the motor is "shuffled" along. If you watch the worm gear while playing a CD it almost trembles to and fro advancing a few degrees at a time. If the sled is sticking the voltage will suddenly start to rise until there is enough force to overcome the friction and the sled jolts forward and which you hear as it jumping.
Mooly,
That's an interesting thought, but if that were the case I think the problem would be consistent across the board with every CD I played, not just a select few. It was this player's ability play some CDs well and others not at all that frustrated me...Oddly enough, it plays every Blue Note jazz CD I have. Do you think there is some kind of regional coding that prevents it from reading certain things--like a DVD player? I've never heard of such a thing, but who knows?
That's an interesting thought, but if that were the case I think the problem would be consistent across the board with every CD I played, not just a select few. It was this player's ability play some CDs well and others not at all that frustrated me...Oddly enough, it plays every Blue Note jazz CD I have. Do you think there is some kind of regional coding that prevents it from reading certain things--like a DVD player? I've never heard of such a thing, but who knows?
There's no regional coding whatsoever on CD. All CD's conform to the same standard. From what you describe it does sound like a pickup issue rather than sticking.
Next step would be to see if the amplitude or quality of the RF signal looked different between CD's it plays and those it has problems with. I would imagine you would see around 1.2 to 1.5 volts peak to peak as viewed on the scope.
Next step would be to see if the amplitude or quality of the RF signal looked different between CD's it plays and those it has problems with. I would imagine you would see around 1.2 to 1.5 volts peak to peak as viewed on the scope.
'Original' Original Meridian 508 CD Player.
Hi Guys,
sorry to drag this one up again.
The OP's title mentions an ''Original Meridian 508''. In most, if not all replies though, people are referring to the CDM 12.4.
I have just been given a Meridian 508 to look at which i assume is even more original than the OP's as it appears to have a 'Swinging Arm' Laser Pick-Up fitted.
It refuses to play Discs. It does Light and I think it is trying to Focus because if the Disc is moved immediately after pressing Play there is the reassuring 'squeal' of the Focus Servo working. The Disc is not spun though and the Display reads ''No Disc''.
Does anyone have any Service Information on this version of this Player or advice on where the problem may lie?
Cheers,
James.
Hi Guys,
sorry to drag this one up again.
The OP's title mentions an ''Original Meridian 508''. In most, if not all replies though, people are referring to the CDM 12.4.
I have just been given a Meridian 508 to look at which i assume is even more original than the OP's as it appears to have a 'Swinging Arm' Laser Pick-Up fitted.
It refuses to play Discs. It does Light and I think it is trying to Focus because if the Disc is moved immediately after pressing Play there is the reassuring 'squeal' of the Focus Servo working. The Disc is not spun though and the Display reads ''No Disc''.
Does anyone have any Service Information on this version of this Player or advice on where the problem may lie?
Cheers,
James.
James,
I started the thread and wish I could be more helpful, but my 508 is the one that says "High Resolution CD Player" and is the 16-bit version. I believe the 508 series was revised three times with 18, 20, and then finally a 24-bit chip set.
I had the laser replaced by a local (DC) guy who worked for Meridian and he happened to have NOS Phillips 12.4 on hand which he installed. It did not have the Phillips "swinging arm" laser pickup (which sounds like a nice variation BTW). Good luck.
Junkie
Hi,
thanks for the replies.
Mooly, there is one 33uF on the HF PCB, it measures OK (37uF actually) capacitance and its ESR are OK. I replaced it anyway and all other Electrolytics on the board but the fault remains.
I have downloaded the Datasheet for the TDA8808T HF Amp IC and that seems to be working OK.
Does anyone have any service info on this unit? Even if from a newer version the secondary Servo processing PCB's may be similar?
Cheers,
James.
thanks for the replies.
Mooly, there is one 33uF on the HF PCB, it measures OK (37uF actually) capacitance and its ESR are OK. I replaced it anyway and all other Electrolytics on the board but the fault remains.
I have downloaded the Datasheet for the TDA8808T HF Amp IC and that seems to be working OK.
Does anyone have any service info on this unit? Even if from a newer version the secondary Servo processing PCB's may be similar?
Cheers,
James.
The caps were worth a try as the 33uf's are the "standard fault" when talking about the swing arm pickups.
Could it be a motor/motor drive issue ?
Although the motor only runs after focus is found... it's got to be worth checking the focus OK line and seeing if the motor drive outputs from the servo uP are trying to tell the motor to run.
As ever finding service info is the problem. There were several different types of motor and drive fitted to early Philips player.
Could it be a motor/motor drive issue ?
Although the motor only runs after focus is found... it's got to be worth checking the focus OK line and seeing if the motor drive outputs from the servo uP are trying to tell the motor to run.
As ever finding service info is the problem. There were several different types of motor and drive fitted to early Philips player.
I don't understand this term in case of quality standart: "do not use oddball or boutique parts"
I think, you mean the marked cap here:
http://obrazki.elektroda.net/7_1269981790.jpg
also mentioned here:
http://www.diyaudio.com/forums/digital-source/181450-marantz-cd-75-se-mk2.html
In some models the value is 33uF, in others 22uF or 47uF.
This cap is in use at pin 17 both by TDA5708 and TDA8808, as I know.
The value isn't critical, but the voltage value. Not, because the voltage has a hugh value in this application. Rather low-voltage caps do have mostly short live time. Therefore I use still 63V versions - e. g. this 22uF/63V version:
http://www.exxelia.com/fichiers/produits/20090409_134615_promisic_co31_relsic_co33.pdf
(Order Code A711723)
also this version is suited:
http://www.exxelia.com/fichiers/produits/20090409_134505_prorelsic_125.pdf order code A701103
Additional I introduce a bypass MKT cap (Wima MKS 0,47uF, 1uF or 2u2).
BTW - this cap is a component of the APC circuit for the laser diode, mostly a RLD78 version from ROHM.
Sanyo OSCON's I haven't check at this place, but nevertheless I can't see specific disadvantages or shortcomings.
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Sorry for the off-topic statement. The correct thread is actually here:
http://www.diyaudio.com/forums/digital-source/203703-help-cdm-1-mk2.html
http://www.diyaudio.com/forums/digital-source/203703-help-cdm-1-mk2.html
Micromega Stage mod or Rega Apollo?
Hi all, I’m new to this so please be patient with me.
I have a Micromega Stage 1.5 from new (due to repair and software update back in the late 1990’s). I’ve had the usual skipping issue, which I have again, so I’ll have to clean the transport and relube again.
I also own a Musical Fidelity M1 DAC.
My question is this, I am willing to upgrade / mod it, but should I cut my losses and buy another more up-to-date (and probably better) CD player like the Rega Apollo?
Hi all, I’m new to this so please be patient with me.
I have a Micromega Stage 1.5 from new (due to repair and software update back in the late 1990’s). I’ve had the usual skipping issue, which I have again, so I’ll have to clean the transport and relube again.
I also own a Musical Fidelity M1 DAC.
My question is this, I am willing to upgrade / mod it, but should I cut my losses and buy another more up-to-date (and probably better) CD player like the Rega Apollo?
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The above question would be better in its own thread. I have moved it here:
Micromega Stage mod or Rega Apollo?
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