After finishing my new ‘base’ for my Marantz CD-94 and constructing a new power cable, I saved up some money for restoring the player to its original glory. It was my uneducated guess that some of the capacitors would have worn out after thirty years, and a recap at least would be necessary. And it was evident that a technician had to take a look at the upgrades that were done to my cd player.
The effect of the yellow 220nf bypass can be considered small, and the same goes for the decoupling with the brown capacitor. A power supply upgrade with two 6800uf capacitors that were paralleled with the original capacitors. This was done by four wires to bridge the gap. Probably this was done to keep distortions from the ‘mains’ out. Upgrading from the NE5534 to AD711JN is arguably better. Money well spent by the former owner shall we say?
The technician that worked on my cd player is also known as a cd player alchemist, some call him the CD Doctor. Unlike the alchemists from earlier times he does not practice alchemy. Instead, he fancies cognac, cigars and tinkering with cd players. When he started working on this project he first took out the extra capacitors, removed the extra wires, struggled with removing the glue. The TDA1541aS1 and AD711JN could stay. But it is nice to know that someone familiar with Marantz and Philips cd player circuits is working on your player. He knows the weak spots of these players and knows how to solve the most common failures on these players. Bear in mind that there also is some cleaning and re-soldering to be done in regular when working on these circuit boards.
Some of the weak parts that need attention on this type of CD Player are the wire bridges, diodes, resistors on the PP16 board. It is a common thing that they will fail eventually after a 30-year life. Glue residue is another enemy of your printed circuit board. Give it a good clean if you have your CD-94 serviced.
If you plan on holding on to your precious Marantz CD-94 or Philips CD-960 for that matter, you would better get your CD player serviced.. My example already showed serious issues that eventually could become dangerous. The big 6800uf capacitors started bulging and were replaced as a precaution.
Keep in mind that the capacitors already have a much lower capacitance and higher resistance. These factors restrict current and consume power. Besides, new capacitors have lower resistance and will make the circuits around them perform as they were designed by the designer. The same can be said about the capacitors in the CDM1, the servo circuit, and the power supply. Some were performing at 30% of their original values, so that had to have implications on the circuits that they were supporting.
My cd player almost had a faulty diode and one transistor. An electronic transistor is essentially two diodes. Diodes and transistors are either in service or not since neither are known to wear out gradually. Any component that goes bad in a circuit can prevent it from functioning. Transistors perform an important duty in circuits, and if they are shorted out or open they will cause the circuit to fail. Test the transistors in faulty electronics to find out if problems can be fixed by replacing them.
Luckily a couple of resistors have been replaced as well. When a resistor fails, it either goes open (no connection) or the resistance increases. When the resistance increases, it can burn the board, or burn itself up. Modern resistors are flameproof and in the past, that wasn’t always the case.
There are rewards as well: after a much-needed recap, your CD player will perform as it was intended to do. Every little detail in the music that you play will be revealed again but be patient: after a full recap, the player also needs a good break-in period. At first, it will sound shut-in and very different from what you have been used to. Be patient as the player will sound better in time.
The work on my Marantz CD-94 was carried out by Bram Jacobse. He is known for a lot of repairs on similar designs by Marantz and Philips. If you want to follow his work you can check out his website:
You could also check out the Dutch forum MFB Freaks, and in particular the Compact Disc section:
The following things were done to my CD player;
- New belts for the CDM1.
- Some wire bridges replaced (rust).
- Bad/damaged resistors replaced.
- Bad transistor and Zener diode replaced.
- Complete recap of the servo, analog and power sections.
- Cracked, fractured or broken solder joints re-soldered on all circuit boards.
- TDA1541a and AD711JN were put on sockets.
- SAA7220P/A replaced by a SAA7220P/B.
- Removed external remote PCB and wires.
- Removed headphone PCB and wires.
- PCB’s were cleaned.
- Siltech mod was taken out except for the TDA1541AS1 and the AD711JN.
- Grundig DEM modification.
- Nichicon bi-polar caps instead of the two Elna’s that were in place.
Next edition of my blog will be about the CDM1 drive section of the Marantz CD-94. Don’t forget to leave your comments and happy listening!