Hello,
I have some questions to the board on the Marantz CD-94 Mk2.
I bought this CD player very cheaply as the owner said that the player is "dead". The reason I bought the player was more for the 2 1541A S1 DAC chips more than anything else.
On switching on, the player do not have any display. I put the player aside thinking of mining the chips at a later time. Fast forward 8 years, I acquired the service manual and after studying the schematics, switched on the player and did checks on voltages.
I traced the no display problem to a faulty 7812 regulator and replaced it, now there is display, good start. I decided that I will replace the electrolytic capacitors as these player is now at least 20 years old, maybe more.
I managed to get into the service loop, loop 0 and 1 only, and can confirm the following
radial swing of of the CDM-1 mechanism is working
the laser emits a red pin point of light
the player accepts commands of play, pause, stop from a Philips same era CD player remote control
On switching on, the laser arm move to the centre of the disc and emits a red light for around 10 seconds, before it is extinguished. This is very encouraging.
The CDM-1 unit has the notorious Philips' "blue" radial capacitor, which is now showing a greenish tint.
The tray mechanism is not working, this could be due to the age of the belts, which I can source and replace.
I put a CD manually onto the tray and clamped it on. I noticed that the gap from the laser to the disc is rather wide, in excess 5mm. The turntable does not spin and the TOC is not read. On pressing lightly down on the clamper mechanism, I can get the turntable to spin, but it needs a sweet spot, a little bit more or less pressure, the turntable will stop. I will have to read the servo schematics to understand this phenomena. But I believe that it is related to the disc to tray gap that I alluded to earlier on.
Before I tackle into the world of lasers and servos, I believe that I should at least get the mechanical parts correct. I read the service manual of the necessary screw to adjust but have not done so, as the screw is nearing the ends of its travel. Someone has messed up this part of the player and did not put it back properly.
Can someone tell me how I can I go about maming adjustments to the tray mechanism and confirming that the clamping of the disc is solely based on the magnetic "puck" on the clamper mechanism. I am quite handy with tools, from servicing my own bicycles. Apologies for the long post.
Thanks in advance.
I have some questions to the board on the Marantz CD-94 Mk2.
I bought this CD player very cheaply as the owner said that the player is "dead". The reason I bought the player was more for the 2 1541A S1 DAC chips more than anything else.
On switching on, the player do not have any display. I put the player aside thinking of mining the chips at a later time. Fast forward 8 years, I acquired the service manual and after studying the schematics, switched on the player and did checks on voltages.
I traced the no display problem to a faulty 7812 regulator and replaced it, now there is display, good start. I decided that I will replace the electrolytic capacitors as these player is now at least 20 years old, maybe more.
I managed to get into the service loop, loop 0 and 1 only, and can confirm the following
radial swing of of the CDM-1 mechanism is working
the laser emits a red pin point of light
the player accepts commands of play, pause, stop from a Philips same era CD player remote control
On switching on, the laser arm move to the centre of the disc and emits a red light for around 10 seconds, before it is extinguished. This is very encouraging.
The CDM-1 unit has the notorious Philips' "blue" radial capacitor, which is now showing a greenish tint.
The tray mechanism is not working, this could be due to the age of the belts, which I can source and replace.
I put a CD manually onto the tray and clamped it on. I noticed that the gap from the laser to the disc is rather wide, in excess 5mm. The turntable does not spin and the TOC is not read. On pressing lightly down on the clamper mechanism, I can get the turntable to spin, but it needs a sweet spot, a little bit more or less pressure, the turntable will stop. I will have to read the servo schematics to understand this phenomena. But I believe that it is related to the disc to tray gap that I alluded to earlier on.
Before I tackle into the world of lasers and servos, I believe that I should at least get the mechanical parts correct. I read the service manual of the necessary screw to adjust but have not done so, as the screw is nearing the ends of its travel. Someone has messed up this part of the player and did not put it back properly.
Can someone tell me how I can I go about maming adjustments to the tray mechanism and confirming that the clamping of the disc is solely based on the magnetic "puck" on the clamper mechanism. I am quite handy with tools, from servicing my own bicycles. Apologies for the long post.
Thanks in advance.
I would start with replacing the belts. My experience is that stiffened old belts does not permit the mechanism fully engaged and the end position leaf switches pushed. The servo would work only when this part is in order. The clamp is spring loaded, not magnetic.
Does the laser move up/down 5 times before the disc spins up?
There is no adjustments on the tray mechanism, apart from the bottom plastic Torxx screw the sets the tray vertical position (the gap as you wrote). It can be adjusted by measuring the focal servo voltage when playing a disc (should be around 0V). I think it is TP4 on the servo board.
Does the laser move up/down 5 times before the disc spins up?
There is no adjustments on the tray mechanism, apart from the bottom plastic Torxx screw the sets the tray vertical position (the gap as you wrote). It can be adjusted by measuring the focal servo voltage when playing a disc (should be around 0V). I think it is TP4 on the servo board.
Many thanks for the quick reply. I will do a change on the belts first before attempting anything else. I saw some of the posts on changing belts on this player, those will be good starting points for me.
I did not get to observe if the laser did move before disc spin up as I was looking from the top.
Again my thanks.
I did not get to observe if the laser did move before disc spin up as I was looking from the top.
Again my thanks.
Oshifis, thank you for the tip regarding the spring loaded clamp. I took a close look at the cam wheel that is operating the clamp and I realised that the wheel is not positioned properly.
A video on you tube clearly shows that the wheel engages a switch which would then activate the loading tray. I very carefully disengaged the c-clip on the cam wheel, and positioned the actuation cam into the proper groove.
I can now see the clamp engaging and the tray being pushed properly.
I've not done a belt replacement yet. Once that is done, I'll power up and see if the open/close functions works. Many thanks again.
A video on you tube clearly shows that the wheel engages a switch which would then activate the loading tray. I very carefully disengaged the c-clip on the cam wheel, and positioned the actuation cam into the proper groove.
I can now see the clamp engaging and the tray being pushed properly.
I've not done a belt replacement yet. Once that is done, I'll power up and see if the open/close functions works. Many thanks again.
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