Philips RCD2 CD transport repair tips

[Studio263]

The Philips RCD2 CD transport mechanism was used in a large number of early 90s CD players and marked a departure for Philips away from the radial swing-arm layout of the previous CDM0 to CDM4 decks. Instead, the Japanese layout was adopted with a sled-mounted optical block driven along by a lead screw and small DC motor. The mechanism was made small so that it could be used in portable players (like the AZ 6893 shown in the photo 1) although it also turns up in full sized models and automatic changers.

To eliminate backlash and to assure quiet running the central gear in the drive train for the sled was made of a soft material. With time this material deteriorates and eventually falls apart, meaning that there is no drive. The player will then not be able to read the disc TOC and therefore will not play.

The complete mechanism was the only part available to repair transport problems with these machines and this now is difficult (if not impossible) to find. Therefore it is necessary to makes one’s own parts to affect a repair. Luckily RS components now stock a pair of suitable gears which can be adapted to form the required part. They are high quality items made by Kyouiku Gear Manufacturing in Japan but they cost less than £3 each, a lot more palatable than the alternatives from HPC Gears which are rather more expensive. The gears have a module of 0.3, one with 14 teeth is required and one with 30. See photo 2, the RS numbers are:

14t: 5031841
30t: 5031920

Some lathe work is required to adapt the parts with the required accuracy. Anyone who does serious work on CD players or tape recorders will eventually need a lathe, so it is a good idea to get familiar with how they work. The book ‘The Amateur’s Lathe’ by L. H. Sparey (ISBN 0-85242-288-1) is back in print and available through Arc Eurotrade, this is an excellent place to start. The lathe used in the pictures is a Sieg “C0”, a tabletop model which isn’t expensive and doesn’t take up too much space – ideal for audio and TV work. These are also available from Arc Eurotrade.

The first thing to do is to form the larger part of the gear by boring out the centre of the 30t part and parting it off to the required width. Start by boring out the centre to 4.3mm with a drill in the lathe tailstock (photo 3). Make the bore deep enough to accommodate the part of the gear which will be cut away when parting off, then there will be less cutting to do at this stage. After the hole is bored, face off the exposed end of the gear and part off to a length of 1.8mm (photo 4). The finished component can then be finished on both faces by rubbing it on emery cloth lightly wetted with oil fixed to a surface plate (use a small mirror if you do not have one). This should leave you with a component that looks like the one in photo 5.

Next, put the 14t gear in the lathe chuck and reduce the diameter of the first 1.8mm down to just over 4.3mm (see photo 6). The object is to create an interference fit with the bore in the 30t gear. Take small cuts and don’t remove the gear from the lathe chuck until the correct size has been achieved. Keep trying the 30t gear on the turned down part of the 14t one until it feels that the 14t gear is just too big for the 30t gear to slip on. At this stage, remove the 14t gear from the lathe and press the 30t gear into place in a small vice (photo 7). Ensue that the vice jaws are parallel and use non-marking soft alloy covers to avoid marking the parts. The remains of the teeth of the 14t gear will create a good fit as they are fractionally distorted inside the 30t gear. Do not attempt to drive the parts together with a hammer; the chances are that the gears will not go together true and the parts will not mesh smoothly.

The last operation in the lathe is to part off the required length to form the finished component. The correct length is 4.5mm, see photo 8. Use a small file and the emery cloth on the surface plate to finish the parted off end of the 14t gear. Clean out the bore of the gear with a 2mm twist drill (held between your fingers) and remove any burrs that may have been pushed into the gear teeth using a craft knife blade. The finished component is shown in photo 9, next to a damaged original.

In order to fit the gear to the RCD2 mechanism it is necessary to remove the plated under the spindle motor. The spindle motor has two pegs separating it from the main body of the unit which can be adjusted to level the disc in relation to the axis of the sled; ensure that these do not move by fixing each with a small piece of putty (etc) before the motor is remove. Ensure that the motor goes back in the same angular position that it was in when removed. Protect the laser by fitting a metal paper clip over the tail of the flexi-PCB to short all the pads together whenever it is removed. Originally, the softness of the plastic gears allowed a little “over mesh” to be applied but this is not possible with a metal gear. Removing the sled motor and filing out the mounting holes slightly oval will allow the motor to be withdrawn sufficiently to give smooth running. Lubricate the gears with a small amount of mineral grease (e.g. Castrol LM). The complete assembly is shown in photo 10. There is no need to fit a circlip on the end of the shaft where the new gear is as the others will hold it in place.

Normal fault finding methods can then be used to sort out any other problems in the assembled player. The gear train will be slightly noisier than the original but aside from this the player should function just as well as it did when it was new.

[Studio263]

Photos 6 to 10 here.

[RojDW48]

A very interesting post. Do you happen to know if this transport was used in the Radford (Woodside) CD player? Mike Davis repaired it for me (useless DAC) and advised that the transports were unavailable. It's a bit sluggish these days and needs help to eject - I dread the time it stops altogether. I know it was a Philips but I am not sure if it was that version.

[Nickthedentist]

Fantastic (as usual), Tim, many thanks.

[Lloyd 1985]

Brilliant!

I'm having problems with a Sony FH-7's cassette deck at the moment, there is a gear made of plastic with the consistency of hard cheese that has stripped it's teeth, it stops the deck from lifting the heads into play. I've bodged it by sticking thin heatshrink over it, but it's noisy and surely can't be doing it much good. I'll have a dig around and see if I can find any gears suitable to make up the broken one.

Regards,
Lloyd