Marantz CD-94 CD Player part 4

The Philips CDM1 drive. Photo by courtesy of Guido Gerrits, vintage-audio-store.

A very important part of the Marantz CD-94 is the CDM1 drive. The CDM1 was produced by Philips in Hasselt Belgium, and at the Sagamihara plant of Marantz in Japan. It was made in special “clean rooms” and most of the workers were female. A Hasselt manager once said that women are simply more capable of “more accurate, precision work” than men. The Philips CDM1 featured major improvements in the precision of all of its parts when compared to the CDM0. The famous Marantz CD-34 (1984) with its unprecedented price tag was the first model in which the Philips CDM1 was employed. Due to the success of the CD-34, Philips/Marantz decided to start producing the CDM1 at the Sagamihara plant. The Japanese CDM1 was first used in the CD-54 (1984) and CD-84 (1984). Later, a special fine-tuned version of the Philips CDM1 was developed in 1986 for use in higher-end players like the Marantz CD-94, CD-95, and the Marantz CD-99. It now has a reputation of being almost indestructible.

Philips CDM1 laser lens mechanism consisting of seven polished glass lenses to bundle the laser beam. Made in Germany by Rodenstock. Photo Credit: analogandever.
Blow up view from the CDM1 from the original service manual.
Up to nine versions were made of the CDM1

The vital factor in the performance of the CD-94 is an accurate read-out of the disc. The CDM1 was made of diecast zinc/aluminum for all sensitive sections to remove unwanted resonance. The complete assembly is floated off the main chassis on massive rubber dampers; a suspension system that assures freedom from vibration and acoustic feedback. Furthermore, the mechanical control circuits have been separated from the CDM-1 mechanism to avoid magnetic interference in the control circuitry and possible vibration from the drive mechanism. Known defects are only of the mechanical kind: dirt on the mechanism/optics or increased bearing resistance. The laser diode on these units rarely needs to be recalibrated and rarely breaks down. The laser itself is a AlGaAs system type. Only the capacitors dry out after 20–30 years of use. According to a document that I found regarding Nichicon capacitor life it is most likely that degradation of your precious Marantz or Philips for that matter starts at 15 years. Some of these Nichicon capacitors can be found on the CDM1 PCB and a recap has to be done after 30 years of use. The CDM1 was widely used by Philips and Marantz but also sold to a lot of other manufacturers around the world. It is also a little bit faster than its predecessor, the CDM0.

CDM1 printed circuit board with original capacitors. Photo by courtesy of Guido Gerrits, vintage-audio-store.

An also common problem with the CDM1 you can encounter is the CDM1 not reading the TOC (the table of contents), refusing to play some CDs or tracks, or occasional skipping. This behavior can be due to the wear of the lower (plastic) bearing plate. This wear can cause problems with the focus and tracking of the CDM1, and it eventually can stop the cd-motor from running. By the way: this is normal wear after more than 30 years of operation and more than 100 million rotations of the spindle axis. If you try to find a replacement bearing (part 51 in the service manual (4822 502 11701), you are in for a challenge. The bearing is almost impossible to find on the world wide web, but it does show up sometimes on flea bay. Luckily people found a way to get around the problem of finding a replacement part. They sand down the top of the bearing, creating a smooth surface again, and you are good to go for another 25 years or so! This website will get you going on your way with essentials on how to service your CDM1.

Top left; Normal and excessive wear. Bottom and middle left; brand new. Top right; minimal wear (Photo by courtesy of Michael Pickwell). Bottom right; new teflon bearing (Photo by courtesy of Matthias Kurz, Solidcore Audio).

The lenses, optical formulations & coatings were originally designed by Rodenstock in Germany, on Philips’ specifications. The seven lenses are made of glass, rather than today’s plastic versions.

Since the manufacture of high-quality aspherical lenses by conventional grinding is not achievable, it was necessary to develop an own machine on which aspherical lenses could be generated. A breakthrough in this field was achieved by Philips in 1978 with the help of the Nat. Lab. developed “ultra-high-precision” numerically controlled lathe COLATH.

The necessary lens optics to bundle and focus the laser beam were developed by the German manufacturer Rodenstock in the prototype stage of the CD development. Their high-quality, light-strong microscope lenses were of central importance because this led to the potential for miniaturization of the information imprinted on the CD.

While most, if not all, Japanese 1982–1986 CD drives have long since died or require extensive surgery, the original Philips heavyweights are still going strong, as if time, thirty years, hadn’t passed. Which is what recordings are all about: to stop time.

The King of the Hill : unmatched and everlasting.

The CDM1 is the King of the Hill: unmatched and everlasting. Although there were quite a few versions of the associated servo/control PCBs and of the motor itself (single-phase vs. triphase), the lens, articulation and diecast chassis remained exactly the same.


Clockwise: Standard Industry (Later Marantz Japan; Sagamihara Old Marantz Factory; Sagamihara new plant (built after Philips took over. Philips Factory Hasselt Belgium. Photo Credit:
CDM1 from a CD-84, Japanese version with brass spindle. Photo Credit: Anton@Inside Classic Audio.

In memoriam; “Music is the highest form of art we humans have created! There is nothing else that has the power to touch people so strongly” — Ken Ishiwata (1947–2019)

CDM1 from a CD-84, Japanese version with brass parts. Photo Credit: Anton@Inside Classic Audio.

Seen as a “high-end” item today, it was the basic base for everybody back then. The CDM1 was found in a lot of CD players and for a reason! The first Philips /Marantz CD player designs did not consider price/margins but had to be simply good. Todays designs do not incorporate glass optics, brass parts, zinc/aluminum die casting, metal trays, and seperate printed circuit boards. Rule of the thumb: The price of a todays CD Player is roughly 10% hardware and 90% shipping, shareholders, marketing and labour. It also seems that everything has to be fully integrated in one chip, lightweight (plastic fantastic) and have to break down within five to ten years. It is not a big surprise to me that people still use the Philips CD-960 and the Marantz CD-94 as ‘stand alones’ or as a transport.

Axial capacitor after 30 years of use. There is one on the CDM1 PCB (C2124(33uf)). This one was in my own CD player and was replaced recently. If your CDM1 goes for maintenance make sure that you don’t forget them. The same goes for the four Nichicon capacitors (C2120, C2121, C2122, C2123(33uf)). Photo by courtesy of Bram Jacobse.

You could also find the CDM1 in the so-called drive-only version such as the Marantz CD95DR, CD12, and the CD99DR. Philips used the CDM1 in the LHH1000. Wadia used it in their drive-only version, the WT 3200 CD transport. However: if you remove the lid of the CD transports you see nothing but similarities between them, heck they almost look like each other!

CDM1 PCB from my Marantz CD94. Photo by courtesy of Bram Jacobse.
Cutting edge Philips CDM-1 radialinear broadcast tracking assembly.

Ken Ishiwata: “After the CD-45LE, we did the 1989 CD-65 and CD-75 Special Edition, and then every year we had a new model, like the CD50-SE, 1991 CD-11 SE, 1992 CD-52SE, 1995 CD-63SE, 1996 CD-67SE, and CD-6000OSE. Each generation didn’t have a new chipset, up until 1989 when Bitstream came, because fundamentally the digital filter was working very well. But we changed the mechanisms — the CD-100 had a CDM0 and the CDM1 followed. This was the original swing arm, complete with diecast parts. Swing arms were the best way, as they had better trackability compared to the linear tracking designs the Japanese manufacturers were using. But it did have its problems. It was heavy, and the position control was done by servos which required high current, and this affected the noise floor. We managed to isolate it, but there were problems nonetheless.

“We ran with the swing arm transports through the CDM3 and CDM4 right up to CDM9,” Ishiwata recounts. “After that, it was linear, parallel tracking like the Japanese. The Philips/Marantz machines always sounded very different to the Japanese rivals for precisely this reason — they had better (swing arm) transports and superior (4x oversampling) DACs and digital filters.

Original servo module. Photo by courtesy of Bram Jacobse.
Servo sub-module. Photo by courtesy of Bram Jacobse.

As Ken Ishiwata already pointed out that the servo print controls the swing arm mechanism. If your Marantz or Philips player is getting serviced don’t forget the servo boards. Let a qualified technician check them and repair them if necessary. In my opinion, re-soldering and a recap are mandatory.

Fully recapped servo module. Photo by courtesy of Bram Jacobse.
Cracked, fractured or broken solder joints repaired. Photo by courtesy of Bram Jacobse.
The recapped circuit board of the CDM1.
Old capacitors, needless to say they have to be replaced after 20-30 years of use. A no-brainer if you’re getting your Marantz or Philips cd player serviced!
Recapped circuit board of the CDM1.
Adding new transport belts. Photo by courtesy of Bram Jacobse.
Finished new belts on the CDM1. Photo by courtesy of Bram Jacobse.

Replacing the transport belts; some tips. It does not matter whether the tray is open or closed. The wire pulley is an obstacle. Don’t remove the wire end from the tensioning spring. It is easier to remove the C-clip from the shaft instead (you could use a small watchmakers screwdriver, or tweezers), then carefully pull the pulley from the shaft, so that you can hang the 1st belt loosely on the inner ridge. This is a critical step because you need to hold the pulley with the wire tensioned until you hang on the belt. Then put the pulley back right away, and secure it with the C-clip. Now you can comfortably replace the other (2nd, smaller) belt between the motor and center pulley, and finally, hook on the other end of the first belt to the center pulley.
The other two belts associated with the other motor can be replaced without removing the pulleys from their shaft, as far as I remember. It just needs some patience and a hook (knitting needle). The rotational position of the pulleys is unimportant because they rotate until the tray open/close switch is engaged.

Reinforced and Optimized new belts for the CDM1. Photo by courtesy of Claire Vandenkerchove. You can order these belts at the Nanocamp (German) or Dindiki (English) website.
New play buttons and a led board can now be ordered at Nanocamp (German) or Dindiki (English) in Germany. Follow this link.
From the original service manual. Photo by courtesy of: Bram Jacobse.

See you at my upcoming new blog about the Marantz CD-94, part 5.

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