1984 Philips CD204 CD player repair

[howard]

Hello again,

I acquired this second generation Philips CD player from a forum member almost 2 years ago for a £5 donation to the Wireless Museum. It was sold as not working, being unable to read the TOC, and apart from a ding in one rear corner of the outer case it is in nice cosmetic condition. This 420mm full width machine is the CD104's big brother, indeed it weighs in at over 9kg ! Apart from size there isn't much difference between the CD204 and CD104, operationally they are the same but the CD204 additionally has a headphone socket.- no volume control for it though. Inside, both PCBs in the CD204 are free from those troublesome griplets found in the CD104, so with the same superb CDM1 CD transport, this machine should prove more reliable than the CD104 long term, that is if it doesn't get damaged like this one was found to be ......that ding in the corner of the case was evidence that the machine had been dropped, which was almost certainly the cause of the damage to be found inside. I have an original service manual for the CD204 and free service manuals are available on the net. Ron Bryan very kindly did most of the work on this machine.

When first powered up the machine wouldn't read the TOC on any CD but it didn't take long to work out why not ... the CDM1 alloy chassis was distorted, damage undoubtedly caused by an impact so when the swing arm attempted to travel it jammed against the chassis which had moved inwards towards it.. An attempt was made to bend a small piece of the chassis back into place, unfortunately it broke off but that did enable the swing arm to complete its travel. However it struggled to focus and track and the voltage output was found to be very low, under 300 mv. So sadly this CDM1 transport was considered a write-off.

I held onto the CD204 just in case a scrap CDM1 transport turned up and almost two years later a CD104 came along with a badly 'got at' servo board so it was decided to attempt a transplant of its CDM1 into the CD204.

It is fairly straightforward to remove the CDM1 from both these players, the assembly and a small PCB attached to the swing arm via ribbon cables lifts out the top after the lid, front panel and tray assembly have been removed, and from underneath, removal of the bottom cover, four bolts securing the transport to the main chassis and finally two screws securing the PCB. The two transports were found to have Philips part number 3104 108 37471 so the replacement was identical, the only difference found was that two extra 0.1uf capacitors had been tacked onto the LM324 op amp next to the turntable motor on the replacement transport - reason unknown. The replacement CDM1 was fitted into the CD204, the machine powered up, a CD loaded and away she went, tracking and navigating perfectly.

However, not all was well as only one audio channel was working. Ron quickly worked out that one channel in the reed relay was open circuit, power to it was fine so the input/output connections were shorted together and the audio came on. The relay was removed from the board, connected to a 5v supply, powered up and tested again and it was then found to be working. Maybe disturbing it sorted it out, so it was reinstated on the PCB and audio now worked fine on both channels.

A final check was performed on the laser, a scope was attached to the decoder board and the eye pattern viewed and it was fine and showing a stable pattern at around 1.2 volts which is typical of these machines. The player was reassembled, it then had a long test and it worked perfectly.

The not so common CD204 model is a very good early CD player as one would expect from Philips. It sounds much the same as the other Philips/Marantz machines of its time, exhibiting good detail, untiring sound quality and a decent stereo soundstage although depth of image IMHO is a bit flat in comparison to the best of them, the CD100 / CD63 and CD303 / CD73. A better quality phono lead would probably sort that, the original one fitted to this example is the flimsiest I've seen on an early Philips.

My thanks to Ron for fixing it.

Howard

[chroma04]

Hi Howard,


An excellent job and write-up.

I do like the look of these early compact disc players. Looks to be well built, too!

Well done!

[howard]

Hello Chroma04,

For just a short period in the 1980s, Philips/Marantz built some exceptionally well engineered CD players. Very little plastic is used in their construction, they are virtually all metal including a hefty alloy chassis and the CDM0/CDM1 transport, even the loading tray is metal - that's why they're so heavy. They sure don't build CD players like these nowadays !

Howard

[ronbryan]

I was just browsing through some old photos taken in 2009 and found a picture of the damaged CDM1 CD drive before we swapped it.

You can see that when the player was dropped on the rear corner, the drive must have moved on its (very) flexible mountings and whacked into the chassis. This was enough to bend the diecast channel that the radial arm swings in. When the arm was driven to that point by the diagnostic, the arm would jam in the channel.

That must have been at least part of the reason why the drive wouldn't track properly over its whole range. However, I think that the optics must have been damaged at the same time, because when the bent diecast bit was removed, the player tracking was still poor. Investigation showed the cause to be very low laser output (eye pattern around 300mV pk-pk). It is possible that the laser could not be made to come into perfect focus after the trauma, as there seemed to be a bit of a kink in the cantilevered flat spring that supports the lens. Whatever the reason, it was decided to wait until a spare CDM1 drive became available as Howard has detailed above.

Ron