I recently picked up a dirty, but good condition NEC CD-730. It does not play discs (and the drawer is misbehaving but I think I have that sorted). It has the same KSS-150A as my Sony CDP-207ESD so I've been using that one to try and diagnose this NEC.
Upon putting a disc in, the spindle motor will spin it about the same amount as the Sony to read the track listing but [DISC] keeps flashing on the display while the laser constantly raises and lowers. The laser continues to do this after the disc stops spinning at least once more (with a faint but familiar click when it drops). On occasion the spindle motor will spin the disc backwards too, but I'm not really sure what that's about.
The laser sled seems to work okay - I've manually retracted it and when loading a disc it will return to its home position fine.
My current guess is that the laser itself is weak. Letting both the NEC and Sony load no disc with a white reflector above the laser, the Sony appears to be significantly brighter.
Would this behavior be in line with a laser that's weak and can't get a focus on the disc?
Thanks in advance!
Upon putting a disc in, the spindle motor will spin it about the same amount as the Sony to read the track listing but [DISC] keeps flashing on the display while the laser constantly raises and lowers. The laser continues to do this after the disc stops spinning at least once more (with a faint but familiar click when it drops). On occasion the spindle motor will spin the disc backwards too, but I'm not really sure what that's about.
The laser sled seems to work okay - I've manually retracted it and when loading a disc it will return to its home position fine.
My current guess is that the laser itself is weak. Letting both the NEC and Sony load no disc with a white reflector above the laser, the Sony appears to be significantly brighter.
Would this behavior be in line with a laser that's weak and can't get a focus on the disc?
Thanks in advance!
this site has been very helpful to me over the years for maintenance and repair of my cd players:
Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives
mlloyd1
Notes on the Troubleshooting and Repair of Compact Disc Players and CDROM Drives
mlloyd1
Thanks for the link!
Oddly enough a second pass of cleaning with some isopropyl (door stop switch, both parts of the laser, the grounding pad on the laser) and it's functional now. I'm getting static during songs on some CDs (mostly newer pressings or CD-rs) so I think I'll need to focus its laser.
Oddly enough a second pass of cleaning with some isopropyl (door stop switch, both parts of the laser, the grounding pad on the laser) and it's functional now. I'm getting static during songs on some CDs (mostly newer pressings or CD-rs) so I think I'll need to focus its laser.
Finally hooked an oscilloscope up to it and while it was pretty well focused, the laser in it (and my 207ESD) seem tired. Their eye/RF measures are about .8-.9v on the scope but ~.2v lower using my multimeter. I assume that's because it's an erratic DC current and my multimeter is doing some averaging.
Replaced the lasers and went through the service manual tuning all of the calibration settings (E-F, eye, bias, focus, etc). Oddly, there is still one CD I have that it just HATES reading. It's picking up a lot of errors (they come over like popping on vinyl) and it shows up over digital out or going through the TDAs.
At this point I just assume it's just having difficulty with the bitstream on this one disc? Maybe it has something to due with the inverting and balancing compared to a single chip player?
At this point I just assume it's just having difficulty with the bitstream on this one disc? Maybe it has something to due with the inverting and balancing compared to a single chip player?
This may be a little too late of a reply, but here goes - I have the same NEC CDP, but oddly, mine uses a KSS240 optical PU, not the older KSS150. If you've adjusted all of the things you can to get a clean eye pattern (with laser output drive within limits) and still get read errors, it may be due to actual errors in the media and/or excess disc warpage. I use a special alignment measurement unit since I work on alot of CDPs, but a clean eye pattern within manufacturer specific levels should allow for error free disc reading. For the most part, the linear travel 3 beam Sony pickups tend to be fussy with CDRs that don't adhere to exact red book standards ie. 80 min orange book 3. Even some brands of read only factory made CDs will generate more than normally acceptable read errors.
The best CDP pickups suited to read most CDR media appear to be the single beam Philips swing arm CDMs. My Creek CDP uses a CDM4 pickup and plays everything I throw at it.
That NEC CD730 also has two TDA1541As running in dual differential mode.
The best CDP pickups suited to read most CDR media appear to be the single beam Philips swing arm CDMs. My Creek CDP uses a CDM4 pickup and plays everything I throw at it.
That NEC CD730 also has two TDA1541As running in dual differential mode.
I know this is an older thread but very little info is available on the NEC CD730. I'm about to receive one after reading what I could about it and the dual 1541 DAC's. What is your overall opinion of the player and are you still able to service these if necessary?
Thanks
Still a very serviceable piece. Laser is KSS240 and most u-con is Sony based. The massive upsampling logic circuit is finicky and probably will need new caps to lower jitter. Otherwise a very capable player. I would convert it to NOS though. Has nichicon muse coupling caps, which can be bypassed if the offset is compensated for.
Thanks for the info. I know it originally had the kss150 with the 210 superseding it, now the 240? I'll try to find information on the NOS conversion. Any suggestions on shops that service these? I'm on the east coast but would ship anywhere.
Thanks