Audio Restoration Project – Repair Philips
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1.2. Audio Restoration Project Repair Philips Magnavox Marantz CD650 CDB650 CD Player Modification This is an Obsolete Text Only Version of this document For the Current Updated Version with Full Colour Pictures please go directly to the HomePage of CONDORAUDIO COM You can download the Current Version directly from our HomePage http www condoraudio com Visit CONDORAUDIO again for many new articles which are added frequently This applies to all similar type models using the Philips CDM 2 and CDM 4 transport commonly combined with the TDA1541 TDA1541A DAC These are found in B amp O s BeoGram CDX2 CD3300 CD3500 CD4500 CD5500 CD6500 CD7000 BeoCenter 8000 8500 9000 9300 and 9500 and selected models from Acoustic Research Arcam Cambridge Audio Grundig McIntosh Mission Naim Rotel SAE Sherwood Tandberg and Tesla Time has proven that this combination of Philips DAC and Transport is probably the most long lasting and mechanically robust ever made and combined with its superb audio fidelity it naturally lends itself to modification in order to extract every last nuance of exceptional sound reproduction Correctly restored and modified the sound quality is superb and it puts many other CD players irrespective of their age to shame This unit came onto my lab bench after showing symptoms of random blackouts on the front panel skipping tracks and difficulty in extending the CD tray Track ski
3. Q10 Schottky units 2 Replace all the PSU electrolytics with high quality Nichicon HE capacitors of equal capacitance except for the main 6800uF PSU decoupling cap 2396 which I replaced with a 10 000uF Panasonic TSHA unit I am not a fan of willy nilly increasing capacitance values in a circuit unless there is a very good reason to do so Transformer overload and damage can very likely occur I much prefer using very high quality capacitors instead which certainly justify themselves by a much more stable current flow This is the Main PCB underside showing the bypass capacitors on the signal coupling capacitors and on the OpAmp Power Supply circuits 3 Replace the signal path area capacitors with Panasonic FM and grey Vishay 138 axial electrolytics of equal value Replace 4 small value electrolytics with red Wima MKS2 film units Do not touch the original polystyrene axial capacitors visible around the OpAmp IC sockets 4 Install sockets for all the IC s more fun later 5 On the underside of the PCB bypass the NE5532 OpAmp s with Panasonic 0 1uF film caps as follows Power Supply Pin 8 to Ground Power Supply Pin 4 to Ground Bypass the 220uF signal coupling caps 2366 and 2367 with 10nF film caps 4 Analogue Filter Display PSU PCB modifications This is the Filter PCB at the left is the Analogue Filter circuit and completely separate at the right is the Power Supply circuit which supplies 32VDC to the Display Panel On
4. and the Focus Drive OpAmp L272M The entire circuit runs much more stably which is immediately evident Copyright Condor Audio Israel 2009 No part of this document may be reproduced or distributed without express written permission as the track information is displayed within a second after inserting a CD This is a very worthwhile mod 12VDC 10VDC regulated 11VDC 10VDC regulated This is the CDM 2 Laser PCB underside showing the wiring changes necessary to accommodate the new regulators The 4 Orange marks show where circuit traces have been cut Do not attempt this mod unless you fully understand the circuit requirements you may damage the circuit beyond repair The power entry point is at Block 33 Pin 1 is 11VDC and Pin 5 is 12VDC The objective is to regulate these 2 unregulated voltages at and 10VDC respectively I used an L78S10C and a LM7910C I located these 2 IC s on empty areas of the PCB which already had solder points for the necessary circuits without needing to do too much surgery The L78S10C with its two film capacitors is at the bottom corner and the LM7910C is in the middle of the PCB At Block 33 Pin 1 12VDC I added a Nichicon PM 100uF 25V capacitor with the ve lead polarity on Pin 1 The Light blue wire is 12VDC unregulated the Purple wire is 11 VDC unregulated the Grey wire is 10VDC regulated and the remaining trace is 10VDC regulated The output of these two Reg
5. assembled the CD player but left the top cover off in order to provide access to the IC sockets 9 Selecting Replacement OpAmps As mentioned in Part 3 above I installed sockets for the OpAmps The amplifier stage has 2 NE5532N Dual OpAmps in the Dip 8 format In its day the NE5532 was a top quality BiPolar OpAmp Today there are better choices The power rails to the OpAmps are 14 6VDC and 14 6VDC This allows us a wide choice of possible OpAmps Most of the newer OpAmps are no longer available in Dip 8 format so I used Brown Dog Adapters to mount the SMD chips I tried many OpAmps and the finalists were the AD797A AD8599 OP275 and OP2134 For pure musical enjoyment and soundstage my ears preferred the OP2134 and that s what s mounted in there permanently Above are some of the OpAmps tried and you can see the 56pF compensating capacitors Output to GND on the AD797A Unused Brown Dog adapters are on the right 10 Selecting a Low Jitter Clock LJC On any CD player adding a Low Jitter clock is an excellent idea to improve the sound characteristics However for most of us budget is a consideration So after surveying the market I selected the NetAudio NOS Non OverSampling mod cost about 60 This is a very easy mod to do as it requires only the removal of the SAA7220 chip and the insertion of the NOS mini PCB a pin for pin replacement This mod bypasses the filtering and oversampling circuitry controlled b
6. ll the new coloured wiring harnesses with Litz wire Copyright Condor Audio Israel 2009 No part of this document may be reproduced or distributed without express written permission Unfortunately the consequential damage from the electrical cutouts was not limited to the symptom of blackouts on the front panel 1 The SAA7210 IC was not performing correctly traced with my Tek 2465B scope and that was replaced from a donor PCB 2 Also two 1 2 bridge 1N4148 diodes 6333 and 6334 had failed and were easily replaced 3 Not surprisingly 6325 BC858 PNP and 6324 and 6326 BC848 NPN had also failed Not having these in stock I substituted BC546 NPN and BC556 PNP appropriately soldered onto the SMD pads 4 On the front panel display PCB 6060 15V Zener had failed it was replaced 5 The TI TMS3763CNL Display Driver IC was faulty so I replaced that also Now that I had repaired all the electrical damage I started on the modifications There are 4 chassis mounted horizontal PCB s in the CD650 series the main PSU DAC PCB with a small daughterboard the Filter Display PSU PCB and the CDM2 PCB There are also 3 vertically mounted PCB s behind the front panel display All are easily accessible for service 3 Main PCB modifications This is the Main PCB showing all the new capacitors and IC sockets For working on the main PCB I planned the work in 5 stages 1 Replace the 8 bridge rectifier diodes 6340 6347 1N4002 with Vishay 11D
7. pping is indicative of a failing laser simple enough but the cause of the random blackouts proved tough to nail down 1 Clean and reassemble the CD tray mechanism On the CD tray I have had similar problems many times before and it is simply a matter of completely disassembling all the plastic toothed gears from the CD tray cleaning off the hardened grease spraying with Silicone spray I do not use grease on plastic parts and reassembling The Service Manual is very clear about the assembly sequence Thereafter I cleaned the V ridge on the plastic wheel with alcohol and replaced the rubber belt I like to use a thicker 1 8mm belt than the original 1 2mm square profile 2 Replace the Wiring Harnesses with Litz wire The cause of the random blackouts was traced to the Stocko OEM connectors whose pincers grip the single strand copper wire in a knife cutting action and over time the wire simply disconnected from the pincer destoying the connection These are the original grey single strand wires in the Stocko connectors Once I discovered this I simply rewired the entire machine using Litz multi strand wiring which is gripped harmlessly by the pincers A pity that the Philips designers didn t think about this before production These are the new coloured Litz multi strand wire in the Stocko connector I would imagine that this problem is going to show up on all the Philips sourced CD650 decks at some time These are the a
8. the filter PCB all electrolytics were changed to grey and blue Vishay 138 axial units Not really intending to use this analogue output I left the NE5532 opamps alone In the Display PSU I changed the main decoupling cap 2922 to a Panasonic EB 470uF unit and replaced the 1 2 bridge diode bypass ceramic caps 2920 and 2921 with 22nF Panasonic film caps This PSU circuit uses a 783M24CT regulator which is bumped up by an 8V Zener diode to attain the desired 32VDC So to prevent regulator failure a common occurrence the current flow should be very stable and that requires using high quality capacitors 5 CDM 2 Laser transport PCB Capacitor Replacements This is the CDM 2 Laser PCB upperside showing all the new capacitors and the Voltage Regulators to stabilize the input voltage Capacitor C2103 33uF is a known troublemaker and replacing this with a 47uF 25V unit usually cures all non laser realted ills in this area For many years in the B amp O technical community we found that unless it was replaced by a Vishay Philips 138 axial capacitor the circuit would remain dead but I am now pleased to report that also a Panasonic FM radial capacitor is electrically quite suitable All the electrolytic capacitors except for 2103 are Nichicon PM but PW or HE are also quite suitable here 6 CDM 2 PCB Focus Drive and Turntable Motor Voltage Regulation This modification regulates the unstable input voltage to the Turntable Motor Control circuit
9. ulator IC s is routed on this PCB to the Focus Drive OpAmp and also goes to Block 36 the Turntable Motor Control circuit 7 CDM 2 Laser replacement and Laser current adjustment Replacing the Laser is a 2 step process firstly installing the new laser assembly and then adjusting the laser current Replacing the actual laser is very straightforward with no complications Insert a CD and select PLAY The 1Kohm potentiometer R3106 at the center of the PCB is adjusted through the bottom hole in the PCB to provide a reading of 50mV which is measured across R3102 I soldered a black and a green wire to R3102 and routed them out of the CD player to my Multimeter The adjustment is very sensitive and I was quite happy with 50 7mV Here you can see the reading of 50 7mV on the Fluke Multimeter 8 Front Panel Display PCB s Capacitor replacement Above is the front most PCB with the new Vishay 138 axial capacitor and immediately next to it is the new 15V Zener diode which was mentioned in Part 2 above To replace the TMS3763CNL Display Driver IC I had to desolder the LCD display completely in order to gain access to the IC underneath it Copyright Condor Audio Israel 2009 No part of this document may be reproduced or distributed without express written permission Above is the Display panel s middle PCB showing the replaced Vishay 138 axial capacitors This completed the repairs and modifications and at this point I re
10. y the SAA7220 and has a good quality low jitter clock A higher quality crystal can be supplied at slightly higher cost I chose the most basic model to see what of kind of improvement it is capable I was very impressed with the dramatic improvement Some techs frown on disabling the SAA7220 s filtering capabilities but it could well be that any possible noise falls outside the frequency range of normal human hearing so I could not discern any audible noise This is a close up of the NetAudio NOS mod installed in the SAA7220 s socket 11 Installation of a Cooling Fan This CD650 is well known for running hot I installed a 12V Thermaltake 60mm square fan at the rear between the Main and Filter PCB s This is a very quiet fan and cannot be heard when music is playing even very softly The airflow is directed from the outside to the inside to provide direct cooling onto some of the hottest components namely the heat sink on the Filter PCB s 24V Regulator Completed Interior Here you can see the NOS mod the socketed OpAmps and all the colourful new wiring harnesses At the rear is the new 60mm square fan for added cooling Parts for this restoration Parts and advice are available for owners who wish to tackle this project by themselves http www condoraudio com yachadm gmail com Copyright Condor Audio Israel 2009 No part of this document may be reproduced or distributed without express written permission
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