Aligning Optical lens in a NAD C-540 CDP

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I've just installed a NEW laser mechanism unit (complete) in my NAD C-540 CDP and I find it still skips on a few discs. Why is this?? Could the focus be off? If so, how do I set it right?

Anyone with a C-540 service manual? Will appreciate very much for all your kind assistance.

Thanks in advance!!
 
:smash: ´Hello. You hame a common problem with me and other NAD owners.My C541 exibhits the same issue. First its a fragile pickup and chipset combination from Sanyo. With C541i, NAD evolute to a Sony transport and chipset. They clame evolution to CD-RW compatibility, but Sanyo L9042 is CD-RW ready too! C541 and olders player with Sanyo solution use L9240 which is not CD-RW ready. I advice to boost the +8V power line. It feeds the motor section and +5 Volts digital line. The motor section comprises the pickup coils, pickup motor, disc motor and tray motor! Its a very power hungry line, the JRC 7808 regulator fail to supply a stable 8V output to the motors, specialy in skip operation or more demand error recovery from system.It will afect +5V line with voltage drop and noise, and wihout enough voltage boost, at least +3v from input to output the traditional 7805 wont play at 100%. So I recommend to get low voltage drop and faster 3 Amps diodes for all power supply. get more than the double, triple if possible (10000uF) capacitance at the first electolytic capacytor (NAD use 3300uF), use the original to boost and clean the +8 Volts output before the 7805 regulator. Change the 7808 to a LM350 arrangement with a good heatsink and a regulation of +8,15 V at least. LM350 can manage 3 Amps, and less than 2V drop at 1,5 Amps, so its easy to drive this line, and mantain enough voltage to the 7805 works fine.Get the service manuals at:

http://www.diyaudioprojects.com/Schematics/index.htm

Use good cd-r media (Sony CD-R) recorded at 4x.
This update should improve sound and track ability of original and cd-r media!

Best Regards
 
:D With my C541 i get more stability in playback to shock and to original cd that have some skiping problem. Still scratch disk, lousy media or hig speed recorded media still have problems!
I'll send to you a document to predorm a mod, but i dont think it get better with this mod, the power supply +8V current boost is more efective in my case!

Best Regards
 

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Some time ago I repaired a Rotel CD player with a similar problem. It had an 8V regulated line that was dropping to 7V or 6V in certain circumstances like outer tracks, scratched discs and sometimes even when first reading the disc. Since the 5V for the chipset were derived from that line and dropping too, the player was hanging and behaving strange and had to be turned off and back on sometimes.

I blamed the power supply at first (naive me), and I built a simple MOSFET low-dropout regulator on vero-board that was able to keep the 8V much more stable but the problem persisted. Current consumption was well over 1A sometimes :hot: and now it was the own mains transformer the one not being capable of providing 8V (drop across my ragulator was under 100mV).

I tracked this abnormally high current consumption to the spindle motor. It was definitely faulty, it was drawing a lot of current and exhibiting little torque at times. The poor driver IC was almost cooking too. I replaced this motor and the problem was completely solved. Current consumption was greatly reduced, it never went over 0.5A or so again...

So if your supplies sag, the first thing to check it that your motors are not faulty...
 
PLS, Eva & megajocke :

Thanks for all the posts, again reconfirming that basically the NAD earlier CDPs have their transport sections poorly executed. Unfortunately, their is not much we can do to UNDO poor circuit designs.

Nevertheless, on my NAD C-540, I've replaced the optical mechanism (complete) twice now and this does come with a brand-new spindle motor so I reckon the faulty issue with the motor is here eradicated. But the tracks still skip inspite of the new optics and I wonder whether is it the poor quality optics or lack of drive from the circuits (which is current starved).

And its getting more and more difficult to get hold of the Sanyo SF-P101N 5/8P optical kits as they too are discontinued now.
 
These voltage drop with the Sanyo pick-up chipset solution is well know to NAD project team. Its represented in the service manual a 7,8V and less figure at power supply pins of the ICs that drive the motors, from 7808 regulator.

Even a +7 volts figure or less is able to drive these chips, see the datasheets of these ics, but i really doubt about the cleaness of the supply energy, which must have impact in the all system. I notice a good diference in sound and stability!
 
PLS:

Going by what you recommend for my C-540, I have located the following that needs to be replaced. They are mentioned below:

1. C122
2. C123
3. C124
4. C311

as per the document NAD engineers published claiming that it improves CD playback from "NO DISC" situation.



5. C529 - presently 3300uF,16V. I can replace this by 10,000uF,16V.

6. DIODES: You said "get faster 3 Amps diodes for all power supply".

Can you please tell me which are these diodes ? The part Nos please, if possible? And with what have you replaced yourself ?

Finally, is my playing CDs likely to improve with all these mods ?

Thanks again!! I appreciate you helping me.
 
:dead: When you ask for service manual, you should be able to understand whats on the schematic diagram. If you are not prepared to understand the basics you should get support from someone that is used to do this mods. To change the diodes you should pay attention to the component dimension and value rate, for instance, maximum current capability, 3 or more (Amperes) and maximum voltage (At least 50V). You shoul shearch a diode reference with high speed and low voltage drop to improve power supply perfomance at all stages!

Best regards
 
:angel: In NAD C541, the secondary winding for +8V is connect to a Graetz rectifier bridge which are D514,D515,D516 and D517! Fuse of this power line is M507 a 1,6 Amp slow burn type. Be sure that your C540 is really similar to C541, or you have to analyse the layout carefully before make any changes!:hot:

Regards
 
The NAD Service Hint specifies capacitor changes for C122, C123, C124 and C311. These changes should be carried-out because it will help focus/tracking/spindle servos to work quicker and more reliably.

Next thing to check is the eye-pattern amplitude. Make sure that it is 2V pp with good reflectivity disks. I explained this here in forums many times before, so use the search engine for more details.

The spindle motor commutators, if dirty and/or greasy, can partially or completely short - circuit the spindle servo and can cause the high current load on the power supply.

The power supply CAN BE designed to allow for sag at spindle motor start up, as long as the voltage regulation is okay during play... cost cutting!

Boky
 
PLS:

I very much appreciate your pointing me towards the 4 x Diodes, Main Cap and C122,C123, C124 & C311 upgrades. I've just put in 3-Amp diodes, 10,000uF cap and the other upgrades. My C-540 is now performing transport functions very swiftly.

Seems circuit board of C540 and 541 are similar.

Thank you once again !!

Cheers
 
The skipping issue still persists.

Reckon its the poor quality optical lens mechanism (Sanyo SF-P101N 5/8P) which I replaced hardly some 4 months back. They are extremely hard to find now as it seems Sanyo dis-continued this model. Maybe the lens is bad or the sled motors in the mechanism bad.

I can't really tell much about the improvement in sound quality since I use the coax digital out of the NAD to my DAC. But I do notice often the NAD as a transport loose is SYNC LOCK with the DAC. What could be the problem?? Any help you can offer?

I do notice quick TOC and <<PREV or NEXT>> functions after the 3A diodes + 10,000uF cap upgrade.
 
Skipping will persist!

:cool: Skipping with original pressed cds that always skip at the same point(s), ceassed, but with old cdrs still persist. With Mitsumi and Sony media recorded with a Yamaha F1 in Audio Master mode at 4X at Nero 6, no problem. I will try a Sony CD-R recorded at a Plextor Premium 2 with Audio Master mode at 4X, to verify!
Did you substitute the +8V regulator for a LM350 solution?
You have to make a dedicated board with a isolated heatsink from the GND (Ground chassis), and connect the LM350 board to the main PCB. The LM350 layout requires a simple circuit to calibrate output voltage and filtering!
If you use an external DAC, why dont you try a cd-rom transport to supply the dac for testing!?
Loosing the synchronicity of the digital data with the DAC (Lock) its familiar with a Audio Alchemy DAC with coaxial link that i test with a Sony ES player! The optical link surpass this issue, but NAD only have coaxial link!Why dont you try too, a converter to get coaxial to optical!
Remember if you dont have a stable and clean +8V supply you get problems at +5V Digital power line! 8 Volts are needed to get the 7805 doing is job rigth, with good ripple rejection!
The original JRC 7808 is designed to supply 1,5 Amps,but even with a optimum heatsink it refuses to drain a stable +8 volts, turning into +7,6V when things get though, which is a scenario of more than 1 Amp, which stress the +8V regulator causing voltage drop and noise!Noise at +8v power line, in my opinion, is the real problem here!

Best regards
 
Thats an interesting thing you've put down. I haven't yet implemented the LM350 solution and you are correct that the present Reg is probably still starving when things get tough!

I never use a CD-R with my NAD, only original CDs. And the skipping doesn't occur at a particular point, it skips as and when it feels like.....very annoying actually!

Frankly - I'm getting a bit fedup with this NAD C540 I use as a transport. And I do have a Theta TLC that I always use which is a Jitter-attenuator. This accepts both Coax & Opt IN while outputs a Coax to the DAC.
 
:confused: Just kick the butt of NAD C540 and get a top transport from TEAC or something a bit less expensive, you´ll hear the diference...!!!Whats your DAC?
Do you consider to buy a good SACD player, with a decent transport with good cd sound?!
Check the reviews!

Regards
 
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