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.