Classic CD Player Modification & Modernisation

Philips CD104 Fixes & Tweaks I have a few CD players which like the rest of my equipment are either the very first of their type or made by QUAD — I purchased the first tray loading CD player from Philips — the CD104 — when they were introduced in the early 80's but within a year it failed — It was returned to Philips who "fixed it" and within a few months it failed again — Philips then sent me a new one which lasted less than a year and this continued until they gave me a CD 104B which was either B because it was Black not Grey like the previous model or maybe they had ironed out the faults and this was the improved B version As it happened the Philips CD104B was an improved version which lasted about 2 years before finally going wrong and then I had to either get it fixed or fix it — By this time the Philips stock faults were becoming well known — Some problems with my first CD104 could be attributed in part to the mechanism but there is one design fault that plagued all the models and it is the through PCB rivets or bushes that did not solder well The bushes are used to connect from the ground plane of the PCBs to the other side of the boards and depending on which ones fail the player does some strange things from spinning fast and continuously to appearing to play OK but drops off the end of long CDs There are 11 bushes on the Philips CD 104 Decoder PCB and 2 on the Servo PCB — The Servo PCB (the one you see when you lift the lid) also uses the leads of electrolytic capacitors to link both sides of the board and these connections are normally OK — The main problem area is the PCB underneath it which is the Decoder PCB
Digital end of the Philips CD104B Decoder PCB — The bush near the OKI RAM IC has been cleaned and resoldered on both sides and pin 12 which connects to ground via this bush has also been soldered directly to the ground plane as have the other pins shown circled in red this is a good way to solve the problem once and for all Another method shown circled in blue — is to replace the bush with a wire link
The Control and Display PCBs mounted on the front panel uses component leads to link both sides of the board and I have seen faults where the soldering has cracked causing the display not to light — Another problem where the display does not light is caused by C 2059 on the display PCB — This provides the reset at switch on for the Display processor and Servo PCB
		Another area where faults are common is the Pre-amp and Laser PCB and on later models the motor "amplifier" on the CD deck From the visible side it looks like there are only a few components on these PCBs but on the other side are hidden surface mount (SMT) components that are either not soldered well or which become cracked when the PCB is flexed due to the player being dropped or connections to the PCB sockets being pushed hard — Failure of the motor to spin or the player to read CDs is often due to problems on these PCBs
Having checked the "usual faults" above if the player still does not work then check the power supplies — I'm sorry — of course that was the first thing you did — after all it's a fundamental rule of fault finding to always check the power supplies first So the PSU was OK but you decide to change the capacitors anyway so while the PCB and Heatsink are out why not fit some better connectors by removing the fixed audio output cable and drilling another hole above the one that is left — You will need to fit some large flanged or insulated Phono connectors to fill the original hole
		The Power supply PCB removed with its heatsink attached New isolated phono sockets with twisted wires are prepared ready to connect to the Decoder PCB — Note screened cable is not required as there is no measurable crosstalk or pick-up due to the twisted wire and twisted ( PTFE wire in this case ) is so much easier and neater to work with
As nice as they are — Gold plated phono sockets with PTFE insulation WILL NOT reduce any distortion — They WILL NOT make the Philips CD104 or ANY CD player sound cleaner or more transparent etc. — Those ridiculously overpriced and so called "audiophile grade" cables that you bought from Russ Andrews could now connect your CD 104 to your expensive passive volume control but they WILL NOT make any improvement to the sound BUT THIS WILL . . .
The two TDA1540 14 bit DACs used in the Philips CD104 derive their binary weighted current sources (each one exactly half the value of the previous) for the 10 most significant bits by time division averaging The TDA1540 data sheet states the accuracy of the current division is dependant only on the equal mark/space ratio of a series of binary divider and this process requires "filter" capacitors which do not need to be close tolerance — However if you look deeper these capacitors appear in the signal path — The ceramic capacitors fitted to the CD104 DAC appear to affect "the sound" of it's output — This is possibly due to losses and or dielectric hysteresis in the capacitors but whatever it is — it is not good —
As you can see on the final modified Decoder PCB above I have changed the "filter" capacitors under the DACs with surface mount (SMT) low loss polyphenylene sulphide (PPS) types — 100nF 16V and 22nF 50V which were readily available at the time in 1210 size — Previously I tried several types of larger wire ended capacitors but this was very messy even with small low voltage types — The 1210 size (0.012" x 0.010") PPS fit well in place of the original 1206 size ceramic capacitors The surface mount components are glued to the PCB underside to enable both through hole and SMT devices to be soldered together — Take care removing the SMT capacitors — Use hot tweezers if you can to heat both ends at once and melt the glue at the same time
		The Marantz CD84 made about the same time as the Philips CD104B used poly? capacitors which can be seen either side of the DACs and although it had a single sided PCB with no ground plane on it's otherwise identical decoder it did (for most people) sound much more natural than the CD104 as did following Marantz players using the Philips chipset For years I owned a CD84 and I still own an original CD104 plus my modified CD 104 which is in my opinion the most natural sounding of them all — The CD84 also has copper / polystyrene capacitors for the output and de-emphasis filters and these could also have an influence on its natural sound as polystyrene is an ideal dielectric for audio
Marantz was acquired by Philips in 1980 so all their CD player designs are actually Philips schematics but it was the implementation of the designs on single sided PCB and thus using leaded poly caps that led to the Marantz getting a better press Some later Marantz models used ceramic DAC capacitors as dictated by Philips but eventually they realised — when the 16bit TDA1541 was introduced and used in many more CD players like the Revox 226 — B&O CD 5500 and Marantz 94 — maybe there was something about poly caps that mattered for analogue audio and the CD880 and DAC960 are proof that they believed so Unfortunately the analogue stage coupling and de-coupling capacitors tend to let the Marantz CD84 down and this was also a problem with the Philips CD104 which had 100Ω resistors in series with the op-amp supplies and ceramic 22nF de-coupling capacitors except for the +Ve supply to the Right channel NE5532N op-amp — This was either a very clever bit of empirical design or most likely an omission on the schematic that got translated to the PCB
Adding better analogue stage coupling and de-coupling capacitors can make a positive difference to the CD104 and many other CD players Analogue output section of my modified Philips CD 104B Decoder PCB — Bottom centre is the Left channel NE5532N op-amp and the two 100Ω resistors either side are feeding its +Ve and -Ve supplies with surface mount (SMT) 22nF ceramic de-coupling capacitors on the other side of the PCB — In the centre is the Right channel op-amp which has SMT 100Ω resistors in series with its supplies but only one 22nF capacitor on its -Ve supply
The original 22µF de-coupling capacitors for the analogue supplies have been replaced with the 47µF tantalum bead capacitors and 4 additional 47µF tantalum beads (marked with orange dots) have been added directly between the ± supplies of the op-amps and the top ground plane by drilling 4 small holes in the PCB — The 2 orange coloured capacitors are the original 22µF solid aluminium output coupling capacitors which are good audio devices so were not changed
		Tantalum and solid aluminium capacitors used for the op-amp supplies and output coupling capacitors are good but still benefit from being bypassed and here 1µF 63V polyester are added across the 4 new op-amp decoupling tantalum and the solid aluminium output coupling capacitors The improvement at this stage is subtle but noticeable if the DAC capacitors have previously been changed for poly caps
So it appears that the current sharing capacitors fitted to DACs like the TDA1540 and TDA1541 as fitted to the QUAD CD 66 do have an effect on the perceived sound and this has been noted by many others and some manufacturers fit them as standard—See picture below — Better coupling and de-coupling of the post DAC audio stages of the CD 104 also makes an improvement in my opinion but the DAC output current is still converted to the output voltage by a transimpedance amplifier and this could be changed . . .
Bang & Olufsen Beogram 5000 series with polyester DAC capacitors	One TDA1541A per channel in Marantz CD94 both with polyester DAC capacitors		TDA1541A in Naim CD player with open polyester caps and other high quality components like tantalum bead capacitors
QUAD 66CD Is a CD player based on a Philips transport and PCB which — like the CD104 — has both through hole and surface mount components and again has surface mount ceramic capacitors for the DAC filtering glued on the solder side of the PCB Unlike the CD104 there is little room between the underside of the PCB and the base of the player so surface mount capacitors — shown circled in yellow — are required 14 x 100nF 16V 1210 size PPS capacitors are fitted on their sides in place of the 1206 ceramic capacitors on the TDA1541A — 3 other 100nF PPS capacitors are fitted in place of the 22nF supply bypass capacitors
To be continued

— Classic CD Player Tweaks —