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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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NAD S500 CD Player
I have this player which is intermittently having problems reading the
audio CDs. It has now started getting worse and needs some attention along the lines of a lense cleaning. Typically it's out of warranty. Does anyone have any experience in stripping down this unit and can offer me advice on sorting this problem out? Thanks |
#2
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NAD S500 CD Player
"tim309" wrote in message oups.com... I have this player which is intermittently having problems reading the audio CDs. It has now started getting worse and needs some attention along the lines of a lense cleaning. Typically it's out of warranty. Does anyone have any experience in stripping down this unit and can offer me advice on sorting this problem out? Thanks You may be lucky, and a lens clean restores operation. The lens should be cleaned using a cotton bud ( Q Tip ) moistened, not soaked, in electronics grade ( 99.7% ) isopropyl alcohol. Although the lens suspension is soft, and quite delicate, you needn't get too paranoid about damaging it. Clean using gentle circular or rolling motions - whichever you feel most at ease with - for a few seconds. then turn the bud around to its dry end, and polish a nice shine back up on the lens surface. And that's about it really. If that doesn't restore normal playability, then you will need to be thinking in terms of a worn laser, although some NAD's do sometimes suffer from spindle motor problems. Usually, when that is the case, the disc will be reluctant to start spinning up. Often, a little 'help' from a finger, will then start it spinning. Arfa |
#3
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NAD S500 CD Player
Thanks Arfa, good advice and mission accomplished, at least for the
lense cleaning. Once I'd taken the cover off I realised that the real problem was that the drive motor sometimes doesn't spin up. I tried the finger encouragement but with no success. Initial suspicion would be a faulty micro switch or similar which presumably enables the motor to spin up the CD once the tray is closed. I don't know specifically how the mechanisim is set up without doing a major strip down which I'm reluctant to do until I've been able to explore all possible options. Do you have any more advise for me? Incidently, i notice the CD drive assembly is of philips origin. |
#4
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NAD S500 CD Player
"tim309" wrote in message oups.com... Thanks Arfa, good advice and mission accomplished, at least for the lense cleaning. Once I'd taken the cover off I realised that the real problem was that the drive motor sometimes doesn't spin up. I tried the finger encouragement but with no success. Initial suspicion would be a faulty micro switch or similar which presumably enables the motor to spin up the CD once the tray is closed. I don't know specifically how the mechanisim is set up without doing a major strip down which I'm reluctant to do until I've been able to explore all possible options. Do you have any more advise for me? Incidently, i notice the CD drive assembly is of philips origin. Could be many things. What is the drive ? A CDM 12.1 or a 2201 maybe ? Usually, the sequence of events is :- tray closes, and "tray in" switch is made. This tells the system control micro that it can go ahead and start the TOC read sequence. Next, the sled motor will normally be driven back and forth a small amount to check that the laser is "home". There is a leaf switch that is pressed by the laser assembly to tell the micro that it is home. The system control micro then turns on the laser. At this point, what happens next depends on the player. Usually, the player will start the focus search operation, which is normally a maximum of three full up-down excursions of the lens, before it gives up, which may be because there is no disc in there, or the pickup is faulty, or the laser is not burning, or weak output. If all is well, the laser should obtain focus within one up-down cycle, and the focus servo will lock and produce a focus true signal. This should result in the spindle and tracking servos being turned on, and the disc should spin up, whilst the tracking servo attempts to lock on the data that should now be streaming off the disc. Once the tracking servo has locked and good data is coming off the disc, the spindle servo will be fine tuned to correct the rotational speed of the disc, and proper data reading will then take place and the disc's TOC will be read. When this has happened successfully, the spindle motor will be electronically braked, and the laser, focus and tracking servos will all be turned off. Some players deviate from this sequence once the laser has been turned on, and just go ahead and spin up the disc to some coarsely maintained speed, whilst focus seek and tracking seek are taking place. Once they have happened successfully, and their servos are locked, the spindle servo will be locked. This sequence of events results in a quicker TOC read from a standing start. Some other players don't give up immediately after 3 focus tries. Instead, they rotate the disc just a bit, and try again, in case there was a jammy fingerprint on the disc right above the lens. This may repeat several times, before the player gives up. The key to figuring what's going wrong on your player, will likely be observation. Try watching carefully how the deck responds when there is no disc inserted. If it seems totally inert, try opening and closing the tray a number of times to see if it ever does spring to life, which might indicate a problem with the tray closed sense switch ( the tray motor might also be trying to still run, even after the tray is fully in ). If it always does something, then try again with a disc in. Try to get it into a position where you can see what the laser is doing under the disc. If it does run up ok, watch and note the sequence of events, then try opening and closing again, until it doesn't work, and see what changed. Also, vice versa. If you see the laser shuffle take place when it does work ok, but not, or in a different way, when it doesn't work, this might indicate an iffy laser home switch. If nothing appears to fundamentally change up to the point where the disc should spin up, between working or not, then you could have an intermittently faulty, or very marginal laser. The Philips ones certainly do fail, and mostly come as a complete deck assembly, and are not hugely expensive. All of this assumes that it is not one of the early Philips radial arm decks, of course ... Arfa |
#5
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NAD S500 CD Player
tim309 wrote:
I have this player which is intermittently having problems reading the audio CDs. It has now started getting worse and needs some attention along the lines of a lense cleaning. Typically it's out of warranty. Does anyone have any experience in stripping down this unit and can offer me advice on sorting this problem out? Thanks Tim, The S500 uses the now discontinued CDM12.4. If the skipping returns, a common problem is lubrication. Cleaning off the old lube and re-oiling the sled rail and idler gear spindle shaft is required. This is rather complicated, as the mechanism must come out of the machine to do this, so if you don't feel technically able to do this, take it to a good service shop in your area who knows this mechanism. Regards, Tim Schwartz Bristol Electronics |
#6
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NAD S500 CD Player
"Tim Schwartz" wrote in message ... tim309 wrote: I have this player which is intermittently having problems reading the audio CDs. It has now started getting worse and needs some attention along the lines of a lense cleaning. Typically it's out of warranty. Does anyone have any experience in stripping down this unit and can offer me advice on sorting this problem out? Thanks Tim, The S500 uses the now discontinued CDM12.4. If the skipping returns, a common problem is lubrication. Cleaning off the old lube and re-oiling the sled rail and idler gear spindle shaft is required. This is rather complicated, as the mechanism must come out of the machine to do this, so if you don't feel technically able to do this, take it to a good service shop in your area who knows this mechanism. Regards, Tim Schwartz Bristol Electronics However, the OP didn't say that he was having trouble with it skipping, rather that it intermittently did not spin up the disc. CDM12.4 mechs are still readily available. Arfa |
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