Cambridge Audio 540C No Disc Repair

This CAMBRIDGE AUDIO AZUR 540C came to me via Freecycle. The chap who kindly offered it said it was throwing a ‘no disc’ error, which indeed turned out to be the case. Opening the player up revealed a few issues resolved herein and highlighted an important warning for users of CD lens cleaners.

The previous owner informed me that he had tried a CD lens cleaner in this player. These discs contain microscopic brushes on their underside that are designed to brush the surface of the lens during playback of the first track. The lens in a CD player is extremely fragile and is also coated in a material that is easily scratched. If there is any dust present on the lens, the very thing these cleaners are supposed to remove, the brushes only push the dirt around and scratch the lens surface.

This cleaner had done even more damage. As you can see from the above picture, the laser once had a dust cover as part of its mechanism. This cover is raised and lowered mechanically when the laser is powered, but had been knocked clean off and was found sitting inside the laser assembly. Reattaching these is nigh-on impossible. There’s no significant surface area to form a strong glue joint and you run the risk of dripping glue into the lens itself. As a consequence a laser that could probably have been saved was scrapped, and a replacement ordered.

This is the superior V2 version of the 540C, which contains many notable upgrades over the original which was part of the first wave of Azur separates introduced in 2003. Key among them are a Wolfson WM8740 24-bit DAC, a toroidal transformer, proprietary servo and better power supply components.

The original 540C used the Sony KSS-213C laser optics and mechanism, replacements for which are easily obtained. This V2 model uses a Sanyo SF-P101N laser mechanism for which replacements are also readily available. Most are not genuine Sanyo parts but the Chinese equivalents work just as well and I’d be willing to bet a few commercial products used them instead of the more expensive genuine part.

The SF-P101N is a low-speed mechanism designed specifically for CD playback. There are two varieties, differing in the number of connection pins on the laser. Most CD players, including this one, use the 16-pin variant. The entire mechanism block including the laser and spindle assembly is available from a number of sellers under different brands on Amazon and eBay from £12 to £20. I picked one with Prime shipping.

I also had to replace the 16-pin flat flex cable as the original disintegrated when I removed it from the player. I’ve seen this happen a few times where the glue holding the metal contacts to the foil separates. This faulty cable could have been the cause of the issue all along, and not the laser itself. As the laser was physically damaged I didn’t test this theory. The cable is a 230 mm 16-pin flat flex cable, the same as the one specced for the KSS-213C.

The top comes off with 8 screws and gives access to the insides. The mechanism is removed by 4 screws, 2 either side, and is connected by 2 cables and the aforementioned flat flex to the servo unit, seen on the left.

The mechanism is flipped to reveal the laser block. 4 screws hold this in place. There is a spring and a rubber isolator at each corner which will need to be transferred to the new mechanism. Note that the springs are often different sizes, so take care to put them back in the same locations.

The replacement is really that simple. There are no electrical adjustments to be made in these players as the servo incorporates a “VLSI (Very Large Scale Integration) circuit which dynamically adjusts in real time the focusing, tracking and output level of the laser for the maximum retrieval of digital information.”

One common issue that these players suffer is a failed tray load belt. That wasn’t the case with this one so I didn’t take it apart but if your tray refuses to open, opens slowly or won’t close with a CD in the tray, that belt is likely the issue. To get at it, unclip the drawer (make sure to remove the switch tab at the rear right) and beneath the drawer you will find a plastic cover. Unclip the cover, slide it to the right and you can lift it off to change the belt beneath. This isn’t an issue limited to Cambridge players though it is an issue that all of them suffer eventually, as do many models from almost any brand you could name.

The second issue this player was suffering was bad solder joints. I noticed that the voltage regulator transistors on the rear board, which houses the DAC, power supply and output stage, were loose. Removing that board revealed cracked solder joints on every single regulator, as well as on the RCA jacks and a couple of smaller components. The existing solder was heavily oxidised and impossible to reflow. It was removed completely and these components re-soldered.

You won’t find technical design like this in a £150 CD player these days. The 540C V2 includes multiple separate power supplies for the D/A converter circuitry, audio filters, clocks and other stages, as well as extensive use of low impedance film capacitors. You can see where costs were cut, in the horrible cheap RCA jacks for example, but even back then this was a lot of CD player for the money. It has control bus and IR jacks too for system integration, and coax and optical digital outputs.

I checked the servo board but there no issues with the soldering on it besides two of the joints holding the metal shield down. These too were fixed and the ground connection to the shield repaired. I also tidied up the cabling.

The result is a perfectly functioning CD player that sounds excellent. Cambridge have always made great CD players and this is up there. The sound is neutral and clean, perhaps what an ‘audiophile’ might call ‘clinical’ but that is better described as ‘accurate’.

I was also amused to note that the transport buttons on Cambridge’s CD players are almost identically positioned to current models. Besides major strides in circuit typology and construction quality, little has changed. The Azur range did, and still does, offer fantastic value for money.

I remember when these were discontinued and were on clearance in Richer Sounds for £29.95, quite possibly the biggest bargain in audio. I believe it retailed for £150 in 2006, £50 less than the 640C which was broadly similar though got you a pair of DACs running in a dual-differential setup with a Double Virtual Earth Balanced topology, and a few other component-level upgrades. There are a lot of them out there and they’re highly affordable. If you happen to be in the market for a CD player, especially one that needs a bit of TLC to get it back into fighting shape, you could do a hell of a lot worse.