Freecycle is a wonderful initiative. It’s a great way to find a deserving second home for things you don’t need and in turn find things that you can make use of, all gifted by strangers in your local area. rarely do I see stereo equipment offered in my locality but a recent offering of a Yamaha CRX-M170 CD receiver sparked my interest. It was listed as having a couple of faults – a temperamental CD player and an erratic volume knob. A quick initial test confirmed both of these faults, along with a few intermittent connections and a cosmetic separation of the aluminium fascia trim with the front display.
Six screws remove the top and reveal the insides. There’s a 50W stereo amplifier based around what appears to be an STK hybrid output module – though unusually I didn’t disassemble things far enough to find out for certain – and a CD player based around Sony KSS-213C laser optics. It has FM, AM and DAB tuners onboard, along with plenty of auxiliary analogue inputs and outputs.
It’s all powered by a generous linear power supply with a hefty transformer accounting for most of the weight of the unit. You got a lot for your money in 2006.
It’s neatly laid out too. The amplifier is bolted to a substantial aluminium heatsink. The preamplifier and CD player control hardware is on the upper-most board at the back with the tuner boards beneath.
I forgot to get pictures of the tuner board while I had it apart.
It’s clear to that Yamaha went to great length to optimise signal paths. The speaker protection relay is right behind the speaker terminals and despite the plethora of cables inside they are neatly routed around the chassis. It’s a well thought out design and surprisingly easy to work on. Modern mini systems of this type have layers of boards and are not nearly as service-friendly.
Fixing this one was relatively straight forward. I first tackled the faulty volume knob. I’ve written up a separate article for that which you can read Here. Essentially the rotating contact wheel inside the encoder wasn’t making good contact, thus causing the system microcontroller to behave erratically.
I noticed a discrepancy in the aluminium trim in relation to the display. This was caused by separation of the glue bonding the aluminium to the plastic subframe of the front panel. The aluminium fascia is held in place by a single screw at the top, and a few clips at the bottom. The plastic is quite brittle and easily broken so use care when releasing the clips. It helps to carefully heat the aluminium to break the remaining adhesive bond, but don’t heat it too much or you risk melting the plastic or the painted lettering. Once I had the front panel apart it looked like it was bonded with a typical double-sided tape, so I cleaned away the residue, added some fresh tape and put everything back together.
Next was the CD player. The KSS-213C laser is widely used and new replacements are readily available for £5, or you can replace the entire mechanism block for a tenner. I decided first to give this one a clean. I used a dab of isopropyl alcohol on the end of a cotton bud, carefully working my way beneath the sliding lens cover and cleaning the lens surface beneath in a circular motion.
I then used the dry end of the cotton bud, and a small air blower to dry any alcohol that didn’t immediately evaporate. Lo and behold, it fixed the issue. The CD player now plays perfectly. A great way to test a CD player is to use a home-burned CD-R, as they are more difficult to read than pressed CDs. The player handles them fine and skips tracks quickly and quietly, which is a clear sign of a laser in good health.
Lastly some dodgy connections were tidied up. There were a couple of plug-in connectors that had come loose from their sockets, and some cracked soldering on the connections around the speaker terminal board and the small adjoining PCB where the terminal board is connected to the preamp board. Those were fixed which resolved the amplifier’s intermittent channel dropout.
I have to say that this is an impressive unit. The tuner pulls in stations well and the AM tuner appears to be Wideband with nice clear highs when you tune a strong station. The CD player works perfectly, and I like the jog-wheel control. You get equalisation adjustments for bass, treble and balance, and plenty of power to fill a modest room with reasonably efficient speakers. These sold very well and are plentiful on the second-hand market for little or no cost and are well worth a punt.
Lovely machine. Trying to fix ours though relative novice. Do you know what the whole cd mechanism block would be called rather than just the Lazer consonant? Thanks
The mechanism block is a KSM-213, though I’m not sure what the loader (I.E the tray assembly) was designated as. What’s the problem with yours? If it’s an issue with the tray getting stuck, not opening or not staying open, there’s a belt in the mechanism that has probably failed. If the tray opens / closes by itself, the limit switches are dirty. Those are the only failures I’ve seen besides the lasers, all easily fixed. If you take the tray out, be careful of the plastic switch actuator clipped into the tray at the rear right corner.
Hi Ashley,
I am a fixer for a local Repair Cafe, a charity whose aim is to reduce repairable items going to landfill, by fixing them for free or a donation. Only parts need to be paid for. I have one of these Yamaha CRX-M170 in for repair, the CD tray does not open when button is pressed. I have removed the CD module and reconnected it outside the chassis, after checking relevant all connections and wiring. We do not have any sophisticated test equipment, just multimeter mainly. There is 5V present at the NO and NC contacts on the CD door drive motor board, this I presume is to tell the processor when door is open or closed. When Open button is pressed it displays OPEN on the LCD display and then after that I presume is looking for CD as OPEN disappears and display reads something else. There is no voltage on the CD tray drive motor when button is pressed. Motor itself seems ok as I have circuit across motor terminals. I’m guessing something (processor) is not telling the door to open and not providing the 5V required. Checked the main board and nothing seems amiss. Any suggestions? Thanks.
Rob
Hi Rob, that’s a curious issue. I would start by tracing back through the motor circuit to see if any components (namely soldered fuses or dropping resistors) have failed open. This isn’t uncommon if the CD tray gets jammed or forced and the motor draws too much current. I’d also check for dry joints in the power supply, particularly around the regulators as they run hot. You can manually open the tray a bit to put the detection switch in its open (neither open nor closed) position, in which case the motor should always have voltage going to it. Then trace back through the circuit ot find out where you’re losing voltage. It is very unlikely to be the microprocessor simply not sending the signal unless the output pin of the microprocessor has blown, but usually when that happens more than 1 of the MCU interfaces fails. The only other possibility is that a motor drive IC has failed, but again that doesn’t usually happen.
Hi Ashley, thanks for the comprehensive guidance on this problem, will check all of that. Just a question, how do you manually open the tray, I did have a quick look, tried moving it gently but couldn’t, but didn’t want to force it. Do I need to take the CD module apart and turn the motor drive?
Between the CD spindle and the tray itself there is a large gear there mostly hidden by the tray, and there should be just enough room to get a finger or a screwdriver in there to turn that gear which will lower the CD mechanism and release the tray. Once you get it released you can slide it forwards by hand. If you need to remove the tray completely there are clips at the rear to either side, but there’s also a small plastic pin clipped into a slot at the rear right of the tray – don’t break it. Some of these mechanisms have a pin hole in the front under the tray through which a paperclip can be inserted to release the tray, I’m not sure if this is one of them.
Thanks, I’ll give it a go when I get some time, probably the weekend.