Thursday, July 24, 2008

The Joy Of CD Player Resurrection

So the first job upon arriving home last night was to attempt some sort of repair on the CD Player of Non-Workingness, that the halls of Chateau Stevie would once again ring with the works of King Crimson, Yes, Fairport Convention, Segovia, David Bowie, John Renbourne, Stan Rogers, Show of Hands, The Beatles, Quantum Jump, Dave Brubeck, Django Reinhart, Joan Armatrading, Emerson, Lake and Palmer, Rick Wakeman, The Electric Light Orchestra, Mecca Bodega, The Police, Mike Oldfield, Squeeze, Laurie Anderson, Roxy Music, Genesis, Pink Floyd, Peter Gabriel, Led Zepplin, Paul Brady, Steve Harley (with and without the rebellious cockneys) and a host of others sitting in the rotating CD Storage Tower of CD Storage including whatever crap Mrs Stevie and her henchwoman-in-training, The Stevieling put on it while I'm not there.

I drove home in the rain to put me in the right frame of mind, and upon arriving at Chateau Stevie conducted a survey of how best to excise the unit from the cabinet.

Owners of modern stereos may not remember that in the good old days between the "entertainment center" and the "ghetto blaster" eras, one assembled one's stereo system out of components that stacked, usually inside a cabinet made expressly to house such stuff and that gave access to the top for the record transcription turntable unit, or "record player" in Dadspeke. By the time Mrs Stevie and I bought this one, the state of the art was such that one need no longer buy each unit from a different manufacturer, but could buy matching amplifier/tuner units, cassette decks, turntables and, later, CD players. Our stuff is all JVC and was bought during the late eighties, usually as "last year's model" to get a whopping discount on the price of ownership. The CD player doesn't exactly match the rest of the stack because it came a couple of case revisions after the rest. The display is the same colour, but the buttons are of a slightly different style. I digress.

Our stereo is housed on several shelves to the left of and in the same cabinet as our TV set. The arrangement of the carpet and the furniture means that the unit can only be swung away from the wall by any significant amount at the other end of the cabinet. Not only that, but the way the wires had been tucked up in the cabinet when the stereo was installed, along with the rather miserable cable lengths allotted by JVC to the various interconnecting bits meant that just removing the unit from the cabinet would be a job not unlike that of changing the clutch on a Leyland-era mini - a job in which one works in a space just wide enough for one's hands, in an area one cannot see and therefore must explore by feel.

I erected a small tray-table in front of the cabinet and managed by dint of this and by partially removing one shelf to get the CD player out of the cabinet and disconnected from the sound and s-bus cables1. The power connection was another matter and required the deployment of some class four swear words to get disengaged from the power tap on the tuner/amp.

Now I had the thing on a portable table it was a simple2 matter to remove the case top and disengage the fascia (which contains all the controls and the display and has to come off so you can get at various moving parts) and place it in front of the unit for testing. I would have disconnected it an many points during the evening's "fun" but the ribbon cable was firmly attached at the chassis board.

The mechanism is as I described yesterday. CD slides are pulled back into an elevator mechanism, which lowers the disc to the transport/playback assembly. Take a look back if you want a more detailed description. I can't face writing all that again. Even thinking about it all gives me the shakes.

I could still hear a whirling motor for a few seconds when the thing was powered up, but it wasn't the motor used to spin CDs. Interesting. I postulated that a gear had disengaged from a shaft somewhere allowing a servomotor to spin freely. Now many of these mechanisms involve worm gears as the first step in getting the motion from the motor to where it's needed, which would normally mandate against forcing anything by hand. The worm gears used in this unit, however, were of sufficiently steep pitch that there was little danger provided one was gentle. The motors would freewheel obligingly if a light touch was used.

I discovered that by manually retracting the slide hook I could provoke the elevator to hunt up and down. That was one servo mechanism that was nominally working then. The disc tray would open, albeit not promptly and not every time it was asked to, so in principle that servo was mechanically sound too. That left the one that worked the slide retracting hook. By dint of gently prying open the CD single play drawer and painstakingly searching inside the mechanism with a flashlight, I found what I suspected: a worm gear lying on the chassis floor and a nearby motor with nothing on its driveshaft.

I had suspected something of the sort once I heard the free-running motor since one of the drawbacks of worm drives is that should the gear chain they are meshed with jam, say by having the linear mechanism it drives over-running its travel and bottoming out, the motor will, if it is turning in the right direction, cause the worm gear to climb off the drive shaft. If the motor is turning the other way it simply runs until the worm gear has worn away and won't grip the shaft any more. The dismounted gear was annoying, but not nearly as annoying as one that had self-destructed and forced a search for a replacement for the by-now obsolete original part would have been. I was, relatively speaking, in luck.

I tried a number of techniques to put the gear back on the spindle without dimantling the entire sub-assembly (something I was not keen to try since precision alignments were involved that I had grave doubts I could reproduce with the equipment in my workshop) but they all ended in swear words. I eventually had to remove the drive sub-assembly in order to get enough clearance to work, which involved disengaging a couple of dozen loose wires from snap connectors (JVC cheaped out on plugs to interconnect boards and components). This alone drove up the anxiety to Galactic Ultra Infarction levels. One dropped tool would result in jumbled wires and I'd never get them back in the right order again.

It took forever, but using a modified dental pick3 I eventually managed to persuade the gear end to go over the shaft, at which point I simply pushed gently on the CD slide retrieval hook while gripping the gear lightly with a haemostat and used the gear train to push the worm gear back into place in a reverse of the process that pulled it off in the first place.

I managed, after much cursing, to re-install the drive sub-assembly in the chassis, then had to remove it again because I couldn't reach to reconnect some of the wires. Reconnecting all the wires, I was then forced to work around them while trying to place screws deep into the chassis and get them in the proper holes to secure the player sub assembly in place, which required placing the screws using the haemostat. It was tedious with a capital Teed and I emphatically don't recommend the procedure to anyone.

I powered the unit on and ran a test.

It worked!

The CD loaded, slid into place and was properly positioned in the playing mechanism and spun up. Stopping it caused the CD to unload as it should. Result! I looked at the clock. It was almost 10 pm. I'd been struggling with the bloody thing for over two hours.

I put the case back together and spent several minutes trying to reconnect the power to the tap on the tuner/amp by feel before I was successful, then connected up the data and sound wires and replaced the unit on its shelf. Drawing breath I loaded In Reel Time4 and was rewarded with the opening strains of "Reynard the Fox". Mrs Stevie came running out.

"It's working? You fixed it?" She asked in amazement.

"Yes and yes" I answered, smugly

"Took you long enough" she sniffed, and returned to her internet friends.

  1. The units communicate with each other and the tuner by means of a rudimentary data network. This is so that when you press the CD button on the tuner, the other units such as the cassette deck, record turntable or radio shut down gracefully. It also enables one to box clever when making tapes, pausing the tape when the record ends and so forth. A really useful feature, long superseded
  2. Ha!
  3. Which had to be bent into a new shape using my trusty Leatherman pliers. All this bending eventually broke the point off the pick and it will have to have its point reground before I can use it for the modelling tasks I bought it for in the first place. It all makes work for the working man to do
  4. Fairport Convention

2 comments:

gil said...

Hi, Stevie,

The forum proved too difficult to fix, so I discarded it and started again. You may want to try again!

Gil

Anonymous said...

Nice to read of this success whilst listening to 'Starless' live from Providence, from June 30th, 1974. The Great Deceiver set. You cannot get more classic Crimson than that.

Jrs