Philips LMSI CM121 and CM201

[amc184]

Hi everyone, first post here on the VCF forums. My background is in hardware electronics, and I have a particular interest in Philips' radial arm CD players (where the laser pivots like a HDD read head, rather than the linear path used in all modern CD players). I found a CM121 for sale, and when I realized it had a CDM-3 laser mechanism (the rarest of the type radial arm mechanisms) I had to get it.

There's very little about the Philips LMSI CD-ROM drives on the internet, and most of what I found was here on VCF, so I joined up and thought I'd share some images and information I found. As well as that, I'd like to get to a point where I can actually use this drive. I've personally never owned anything earlier than a socket 370 Pentium 3, so I'm not that familiar with the computers of this era.

Anyway, I thought I'd start off with a teardown of the drive.

Unfortunately my CM121 has seen a fair bit of sun, and most of the plastics have browned a little, especially the front panel label. This post has a CM121 that must have spent its life in the dark, and there's quite a difference.

I later found out that there's a SCSI version of this CD-ROM, and looking at the back panel's plastic moulding, it's pretty obvious.

The full model number is CM121/00, and it was made in March 1989 in Vienna, Austria.

Four screws remove the panted steel top and sides cover. This shows the major components of the drive:

• CM201 internal CD-ROM drive
• Hitron HSG19-21 AC to DC power supply
• Audio output board
• Internal to external LMSI converter board
• LED, fan and DIP switch board

The audio output board is something significant that the CM121 adds. The CM201 doesn't include a DAC or analog audio output for use with CD audio playback. Instead it has a digital audio output, but not using SPDIF like you might expect - it is I²S, a bus usually only used internally within a device. The size of this board shows why. At this point audio DACs were still pretty new, and Philips was still using the TDA1541A, their third audio DAC (after the TDA1540 and TDA1541). Along with the separate SAA7220 digital filter and the complex supply requirements (+5V, -5V and -15V), there just isn't room for this in the CM201 itself. Later LMSI drives like the CM206 used the simpler TDA1543, which could be accommodated in the drive.

The LMSI bus used between most LMSI CD-ROM drives and an ISA card in the host system has two electrical formats. For internal drives like the CM201 it is single ended 5V TLL, and for external drives like the CM121 it is a differential 5V signal, similar to RS-422. This converter board converts the CM201's IO to the external format.

The last board is used for a number of miscellaneous functions:

• It takes a 12V feed from the power supply, the same output supplied to the CM201
• It provides an output to the Sunon SD1206PTS2 fan. It looks like there's some temperature control for this fan, using IC1 (LM358 opamp), T1 (BC328 transistor) and R4 (some kind of temperature dependent resistor probably).
• It provides an output for the front panel power LED, simply the 12V run through a resistor.
• There's also a DIP switch that aligns with a plastic knockout on the rear panel. That knockout is left closed on the CM121, and there's no cable to ST4. It might be used for something in the SCSI model.

Another major part is the power supply, a Hitron HSG19-21. It's pretty impressive that this 1989 built power supply is still going after all this time, I've seen plenty this old die. I certainly measured it's output while disconnected from the CM201 before I powered the whole CM121 up, and it was a solid 5 and 12V. I don't trust it long term though, and I'm debating whether to replace its capacitors or design a new replacement power supply entirely. If you have any information and ratings on the HSG19-21 please let me know.

(continued in second post)

 

[amc184]

Of course the most important component is the LMSI CM201 internal CD-ROM drive. The version used in the CM121 has the front panel removed.

It was made in February 1989 in Eindhoven, The Netherlands.

Inside the CM201 is what I bought it for, the Philips CDM-3. This mechanism seems to be the first developed by Philips for compact applications, and that's why it is rare - apart from a couple of exceptions it was only used in specialist applications where the small size was needed. The CDM-0 or CDM-1 used in the CM100 are about three times the height of the of the CDM-3, and impossible to use in a half height 5¼" drive bay.

This drive is still using a lot of DIP package ICs, so space was created by adding two sub boards to the mainboard. The main parts I see on this board and their functions are:

• TDA5708 and TDA5709 - these are the servo chipset, controlling the focus and tracking of the drive, and are the same as what you'd find in many CD-audio players. It's the first time I've seen the TDA5708 in an SOIC package - it does save a lot of space over the DIP package normally used. The TDA5709 is the IC with the heatsink slug.
• LM272s and NE5532 - these power opamps will be driving the focus and tracking coils and spindle motor.
• SAA7210 - this ASIC does the actual laser signal processing and outputs digital data. The 11.2896MHz crystal will be clocking this at 256 times the standard CD audio sample frequency of 44.1kHz. The MN4264 DRAM is its frame buffer.
• SCN8031 - a Signetics licenced Intel 8031 ROM-less microcontroller, which will be controlling the drive and probably handling the command part of the LMSI interface. There's also some kind of ROM next to this.
• PCF1801 - I'm not sure what this is doing. Philips usually used the PCF naming for ASICs.

One of the sub-boards can be detached.

And the other cannot be. I'm really not sure why you would have this variation.

With the board assembly removed you can see the laser mechanism and loader most clearly. This drive uses a caddy, which I don't have, so I haven't seen the whole operation. The caddy has two parts, an outer shell and a lobster claw. The CD fits into the lobster claw. When the caddy is inserted the lobster claw clips into the far end of the drive and remains in the drive, and the outer shell only is withdrawn. Inserting the empty outer shell back into a loaded drive will clip into the lobster claw, and the CD and complete caddy can be withdrawn.

There is a bar at the mouth of the drive which is depressed when a caddy outer shell is inserted. This closes a microswitch, seen at the bottom left below with yellow leads. When this switch is closed the spindle stops immediately - this makes sense as the caddy outer shell is inserted when the drive is being unloaded or loaded, and is not present during playback. There is no mechanism to sense the presence of the lobster claw or CD, and the drive will attempt to read every time the switch is released.

Anyway, I hope this is interesting to the owners of the other dozen LMSI CD-ROM drives still out there! I'll be back to post more information I've found, and hopefully make progress towards my actual goal - to use this drive to read a CD.

 

[amc184]

To actually make use of the CM121 the more obvious solution is an ISA card. I've see a few options:

• CM153 - this seems to have been the standard option for the CM100, CM201 and CM121. This card has both the internal and external variants of the LMSI bus, and fortunately consists entirely of generic components. This allowed Shelby Jueden to successfully reverse engineer and recreate the board - see his Youtube Channel and Git Hub.
• CM50 - this model number is used for both an ISA interface and the portable drive it went with. This one uses an ASIC in a DIP package, so can't be easily reproduced. It also supports both the internal and external LMSI interfaces, which is odd since the CM50 is specifically an external drive. The only place I've seen picture of this card is in this German forum post. It also outputs 5 and 12V supplies on some pins of the external connector, as the CM50 uses a single cable for data and power.
• CM250 - this card was probably released with the CM205 CD-ROM drive. It uses a second type of ASIC in a PLCC package (NCR DIGBIE LMS). All the examples I've seen in photos have only had an internal LMSI interface, but the card does have patterns for an external interface as well.
• CM260 - this card is pretty similar to the CM250, and I'd guess it was released along with the CM206. It uses a third type of ASIC, this time in a QFP package (NCR DIGBIE2 LMS). Like the CM250, I've only seen photos where the parts associated with the external interface are not installed.

As far as I'm aware the CM206 and CM260 were the last real LMSI products, and the following CM207 is a rebranded Japanese drive. I haven't seen anything suggesting that there's a PCI LMSI interface card. For someone like me without a vintage PC collection, an ISA card is a pretty big hardware limitation.

The next issue I see is OS and driver support for these cards and drives. There's a great archive of various LMSI drivers here. I downloaded everything remotely relevant from here like a true data hoarder, and what I found was:

• There are two sets of drivers released between 1989 and 1992 that support the CM153 and CM154 cards (whatever a CM154 is) for MSDOS. These seem to allow the use of the CM50, CM100, CM201 and related drives. They might also support the newer CM205, CM206 and related drives, but its not clear.
• There's a package that combines CM153 and CM250 cards for MSDOS, but has no information.
• The later packages support the CM250 and CM260 for Windows 95 and NT, but only with certain drives. It seems like partway through the production of the CM205 the way the drives behave changed, maybe something to do with support for multi-session CDs. These drivers won't work with drives before the revision E CM205.

For my CM121 this means I'm probably limited to MSDOS and the CM153, or maybe the CM250.

Somewhat hastily I bought a CM250 that I saw come up at a good price shortly after I bought the CM121. Like others I've seen photos of, it doesn't have an external LMSI interface. I don't have the card to hand yet, but from photos I've been able to reverse what would have been installed in the unpopulated patterns to support the external interface. After verifying a few things when it arrives I should be able to add an external interface. I'll share the details on this here when I'm done.


However ...

There is another option that I've seen which might allow more flexible use of LMSI drives. As you'd expect from the plastic moulding on the back of the CM121, there are SCSI versions of these drives. From what I can determine all of the internal drives (CM201, CM205 and CM206) are LMSI interface only, but a LMSI to SCSI interface board called a CM161 could be used with them. Some drawings I've been able to find:

The combination of a CM201 and a CM161 was called a CM210.

A CM121 with a CM161 mounted inside was called a CM131.

DEC also marketed versions of the CM201, CM121, CM210 and CM131, which confusingly were all called the RRD40. The internal SCSI version of the RRD40:

The external SCSI version of the RRD40, with two stacked in a typical SCSI setup:

There are photos of this CM161 board online right here on VCF. I've taken a look at it, and like the CM153, it uses a pretty generic set of parts with no custom ASICs. A lot of what it uses is obsolete of course, but all are still fairly well available at reasonable cost on the grey market. The major parts are:

• NCR 5083 - SCSI interface IC. There are functional equivalents from other manufacturers, including AMD (AM5380), Logic Devices L5380, National Semiconductor (DP5380) and Zilog (Z5380). There are also CMOS versions (53C80), but these are not pin compatible with the original 5380, and may operate subtly different.
• Philips 80C31 - ROM-less 8-bit microcontroller. This is a licenced version of the Intel 80C31, so this could be used also, along with other licenced versions.
• NEC D27256 - 32k x 8b EPROM. This is an additional complication, but it should be straightforward enough to read out and archive this ROM.
• Hyundai HY6264 - 8k x 8b SRAM.
• Goldstar GM76C28A - 2k x 8b SRAM.

The rest is glue logic and passives, all pretty easy to get.

There's next to no chance of finding one of these, but if anyone out there would consider selling or lending one to me, I think that like the CM153 it would be possible to reverse engineer and reproduce this. Using SCSI has it's own issues, but it seems like it would be a lot less limited than LMSI.

I've made a lot of assumptions on some pretty thin information in this post, so please do correct me where I'm going wrong, I'm here to learn.

As a final word, here's where I think a CM161 board would go in an CM131:

 

[amc184]

Earlier in this thread I clumsily tried to describe the operation of the caddy with a CM201 or CM121. There's a great diagram from the RRD40 manual:

The step are reversed to withdraw a disk. A diagram showing the two parts of the caddy:

 

[tingo]

Nice write-up. Thanks!

 

[AndyWang]

I have CM121, RRD40 SCSI, I have successfully used the CM153 card to get the CM121 to work and play music, however I cannot drive the CM201 using the RRD40 card, it recognizes it but is garbled.

 

[AndyWang]

这是 LMSI 转 SCSI 卡。可以识别CM201，但不能播放音乐。

 

[amc184]

Thanks for posting Andy, I'm aiming to get to a similar point with my CM121 soon. I've now also bought myself a CM206 drive and CM250 and CM260 ISA cards. I'm planning to modify at least the CM250 to add the external LMSI bus as an option, but I think ultimately I may need a CM153 to use a drive as old as the CM121 / CM201.

A few questions about your RRD40:

• What version of the RRD40 do you have? Is it a CM201 equivalent plus the LMSI to SCSI board or is an enclosed external variant, similar to the CM121?
• Are you saying the the LMSI to SCSI board works with the DEC drive, but not the regular CM201 from the CM121? Or something different?
• Have you noticed any difference between the DEC and LMSI drives? Maybe the firmware on the rearmost vertical board of the CM201.

 

[amc184]

I've also slowly been doing more on this subject. As I said above, I've now got a CM250 ISA card. The CM250 and CM260 LMSI interface ISA cards both have PCB patterns for an external LMSI interface, but I've never seen any images of a card where those parts are fitted. To support my CM121, or at least try it with a CM250, I wanted to look at populating this section of the PCB.

I started checking the CM250 based on online photos even before I got my own example. Fortunately it's a very similar circuit to the one of the CM153 that Shelby published. I've drawn it in the attached PDF and below:

There's one interesting thing it does that is different to the CM153. At the drive end of the internal LMSI interface pins 2, 4, 15 and 16 are ground. One the CM250 end pin 16 is not connected to ground, but is connected to the line receiver's enable pin and pulled up to VCC. This means that when a drive is connected to the internal LMSI interface then input from the external interface is disabled, and the two cannot conflict (with the internal interface given priority). It's a good idea, but I bet it's led to some confusion when the external interface didn't appear to work because it was already in use with an internal drive.

Here are some photos of the CM250 before I did anything:

And here's what it looks like after I added the related parts:

Unfortunately the DB25 connector has a somewhat unusual footprint, and the standard one I have won't work. I'll update when I've found the right part, but in the meantime the parts I added were:

Reference	Part Description	Part Used
C9, C10	Capacitor, 100nF, 10V or greater, 1206	Yageo CC1206KRXR7R9BB104
R1, R18	Resistor, 1kR, 1206	Yageo RC1206FR-071KL
R4, R6, R8, R9	Resistor, 220R, 1206	Yageo RC1206FR-07220RL
R5, R7, R10, R11	Resistor, 270R, 1206	Yageo RC1206FR-07270RL
R12, R13, R14, R15	Resistor, 120R, 1206	Yageo RC1206FR-07120RL
U1	Quad RS-422 line receiver	Texas Instruments AM26LS32ACDR
U2	Quad RS-422 line driver	Texas Instruments AM26LS31CDR

There are many other options, this is just what I used.


As well as this, I designed and made a new power supply for my CM121. I don't really trust these old SMPSes, this one was working, but it was loud and I've had bad experiences in the past. For the replacement I used a Meanwell IRM-30-12 for the main 12V rail, and a non-isolated DC-DC switcher for the 5V rail. It seems to work well, though I haven't got a set up to fully test the CM121 yet.

Here it is installed, using the original mounting bracket and AC input harness with a new output harness:

And on its own:

 

[Timo W.]

Instead of trying to modify a rare CM250 card, why don't you just build yourself a CM153 card?

GitHub - AkBKukU/CM153-Repro: A reproduction of the Philips CM-153 LMSI controller

A reproduction of the Philips CM-153 LMSI controller - AkBKukU/CM153-Repro

github.com

You can also see there how things work.

The CM153 would be the correct card for your drive. I can tell you for sure that DIGBIE-based cards won't work. They implement a newer version of the LMSI protocol that is not compatible with these old drives.

 

[amc184]

I'm aware of Shelby's reproduction CM153 card, a great project that I did mention a couple of times in my post. It's something I may build in the future, especially if I'm not able to get the CM250 to work with the CM201 / CM121.

I don't think what I've done to the CM250 really diminishes it, as I'm adding parts that presumably some version of the card did have. I also may use my CM206 with the external LMSI bus, as the luggable PC I'm getting to use all of this with unfortunately doesn't have an internal 5¼" bay.

 

[Timo W.]

especially if I'm not able to get the CM250 to work with the CM201 / CM121.

You won't. As I said, the DIGBIE can not work with these drives. Tried that many years ago already and even Shelby tried before he started cloning the CM153.

If you need some background info: the early drives send data just as it was CDDA and it is up to the driver software to do all the data processing. With DIGBIE, they put most of the processing in hardware to allow drives faster than 1x without taxing the CPU too much. That means: the original drivers won't work, as they don't get the raw data they expect, and later drivers for DIGBIE have no support for the older drives. It's simply not going to work.

The oldest drive you can get working with DIGBIE is the CM50. And that is only because there is one driver for it that supports this single combination (which is odd by itself, as the CM50 needs power over ext. LMSI, which DIGBIE cards normally don't provide).

 

[AndyWang]

Thanks for posting Andy, I'm aiming to get to a similar point with my CM121 soon. I've now also bought myself a CM206 drive and CM250 and CM260 ISA cards. I'm planning to modify at least the CM250 to add the external LMSI bus as an option, but I think ultimately I may need a CM153 to use a drive as old as the CM121 / CM201.

A few questions about your RRD40:

• What version of the RRD40 do you have? Is it a CM201 equivalent plus the LMSI to SCSI board or is an enclosed external variant, similar to the CM121?
• Are you saying the the LMSI to SCSI board works with the DEC drive, but not the regular CM201 from the CM121? Or something different?
• Have you noticed any difference between the DEC and LMSI drives? Maybe the firmware on the rearmost vertical board of the CM201.

I have is the SCSI version of the RRD40
The RRD40 I own also has a CM201 driver and an LMSI to SCSI board inside, but it is missing the audio decoding part.
I have two different LMSI to SCSI boards, the RRD40 version and the CM210 version. Regardless, both boards only recognize the drives and display garbled characters (DEC RRD40 and CM121 and CM201), or it could be my SCSI adapter. Not compatible
I don't think the CM121 I have is much different from the DEC RRD40, just a simplified variant

 

[JasonZhao]

You won't. As I said, the DIGBIE can not work with these drives. Tried that many years ago already and even Shelby tried before he started cloning the CM153.

If you need some background info: the early drives send data just as it was CDDA and it is up to the driver software to do all the data processing. With DIGBIE, they put most of the processing in hardware to allow drives faster than 1x without taxing the CPU too much. That means: the original drivers won't work, as they don't get the raw data they expect, and later drivers for DIGBIE have no support for the older drives. It's simply not going to work.

The oldest drive you can get working with DIGBIE is the CM50. And that is only because there is one driver for it that supports this single combination (which is odd by itself, as the CM50 needs power over ext. LMSI, which DIGBIE cards normally don't provide).

Hello buddy，i want to buy your 2 philips cd caddys，is it ok？

 

[Timo W.]

I don't have any Philips CD caddys for sale. I sold the spare ones I had quite some time ago.

 

[JasonZhao]

All right thanks，I have one cm201，but no cd caddy to use，I can't do anything about it.