NAD C541 Tray Problem Repaired

Spacer doesn't work

A spacer prevents the CD from being positively centered, so it would be liable to wobbling, making it difficult to track. I wanted to see if I could refrain from using a tighter belt to avoid putting too much pressure on the bearings in the motor. I'm in the US and O-rings at the local Ace hardware are not designated by number so I will have to see what matches the drive belt.


CAUTION - I don't advise or dis-advise the following, just posting for informational purposes
Someone on another site had this to say about D701: "It seems that these players have a construction flaw. Look for D701 on the main board -- near the cables that run to CD transport. You will find in that place a small 7.5 kOhm rsistor. This should be a 6.2 Volts Zener diode instead. Replace the resistor with 6.2 V Zener and the tray becomes strong and fast."
http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1319855242

I don't see how this is possible because the problem is not the motor, which is the only thing that could be affected by the D701 component, whatever it is supposed to be. The problem is that the magnet is too strong for the belt/linkage to break the magnetic bond of the the upper and lower clamps of the CD spindle. As everyone who has this problem knows, the motor can be heard spinning when the door does not open.

In short, I believe the only solution is a slightly tighter belt.

Jack
 
The reason the drawer won't open sometimes is because the motor, rubber drive belt and linkage have to first overcome the magnetism of the spindle assembly that clamps onto the CD when it is inserted....
Jack, a magnetic spindle clamp is common in CD/DVD drives. Keep in mind that the magnet is not growing stronger with age. Rather it is the rubber belt getting old and starting to slip under load. A multitude of reports of the same problem with C541 tray indicates that its original NAD belt deteriorates after 8-10 years.

After you replace the belt, I would recommend replacing the D701 resistor with a 6.2 Volt Zener diode - as pictured and described above.

The O-ring I used fits well, but do make sure to remove with rubbing alcohol any greasy lubricant from it and any dirt from the two pulleys. It will continue to slip when greasy.
 
Hi, Gary, thanks for the advice. The reason I thought it might be poor design more than the belt stretching is that mine had that problem almost fresh out of the box, but pressing the open button several times in succession always opened it within 3 or 4 tries, so I lived with it. But now I might want to sell it so I had to try to deal with it. At any rate I swapped the belt out for an appropriate sized O-ring. Cleaned everything with 91% alcohol and buttoned it up. I just downloaded the service manual and I will look at the schematics to see what sense I can make of D701. Okay, I see what you are getting at with the zener. Pretty good work digging up the pinout of the motor controller. The fix looks easy enough. I might even have what's needed in my shoebox full of spare parts. On the other hand, I have no problem with the tray speed. It's not sluggish at all on this unit. If I do make the patch I will post my results on this thread.

Jack
 
Jack, replacing the resistor marked D701 with a 6.2 Volt Zener gives the motor an extra horse power ;). Since the motor does everything: loads the tray and moves the transport up and down, the little bit of extra kick may help it and actually fix your problem.

If you find a 6 Volt Zener, you might do what I did, break the resistor in half, wind the Zener's ends around the legs of that resistor and solder it from the top. That way you would not need to remove the main board. If you are good at soldering then this would be really easy to do.
 
c541 tray issue - dioide help

ok my c541 has tray issue also. over the years it worked after a few tries, now, just opens and closes at best. I tried a new belt from MCM, but no luck.

after taking it apart, noticed spin motor not lifting up, if I help it by rotaing the gear in front, it will play. lubed all guides (not belt or pullies!, cleaned pullies with alcohol before putting on new belt)

so, thinking of trying the 6.2v diode trick...what wattage should the diode be, saw 1/2 watt, 1 watt etc....

thx, any advise appreciated!!
 
Elwood, either 1/2 Watt or 1 Watt 6.2V diode will work. Make sure its polarity corresponds with the symbol on the board. See picture below. Please, post the results when done.

If you decide to cut the resistor and solder the diode from the top side of the board, like I did, prior to soldering twist its legs tightly with a single turn on each side around the resistor's ends - this will hold the ends in place while soldering. A 1/2 Watt diode will have thinner legs = easier to twist around.

Notes:
1. If you leave the resistor intact, adding a 6.2 Volt Zener will make no difference.
2. If you cut the resistor and leave it without a Zener, the chip will send full 12 Volts to the motor - which may cause a damage.
3. Where to buy a 6.2V Zener? Ebay (pick a US seller for fast delivery), Radio Shack ($7 shipping!), Frys, local TV repair shop.

diodee.jpg
 
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Swapping resistor for diode

Gary,

Even though replacing the belt with an O-ring solved the sticky tray problem, I got curious about swapping the resistor for the diode and I did as you suggested. As a result, the drawer is definitely faster. I attached a photo of the repair. I left the resistor intact just in case. I had to buy 2 diodes to get 1, so if anyone wants one, it's yours for a buck and a half :) I also enclosed a Gary Larson cartoon that is taped up near the counter at the local mom and pop electronics supply store where a bought the diodes. I wish it was that easy. Enjoy!

NAD diode 001a.jpg

Gary Larson 001b.jpg
 
I'm having similar problems, but I have the 541i. I pulled the belt, and it was actually smaller than the #29 O-ring. The problem seems to be with the motor not lifting. I'm going to try a smaller O-ring, and get back to you, but the motor will run, if I push lightly on the wiring plug that goes into the assembly with the lens and motor.

So, any ideas as to whether this is a belt issue, or resistor (given the new design)?
I found the 541i service manual, and following its "Troubleshooting Guide" it says to check "Focus Signal Output" or "Check Connection or Pickup". I am assuming that the belt issue would be in the "connection or pickup" department, but any ideas on how I could check the focus signal output? I guess the screw on the back of the Laser would be some sort of focusing mechanism, and the screw part of it would be more akin to adjusting DC offset than something that would actually raise and lower the motor?
I dunno, I'm kinda stumped at the moment. :confused:

Thanks for any help or suggestions, and thanks for all the previous documentation! Jon
 
I'm having similar problems, but I have the 541i...
Hi Jon, if you are having problem with the tray not moving in and out adequately fast and/or the laser assembly not raising to its position - both of which are driven by the same motor- then the very first (and in most cases: the only) culprit is aging rubber belt. Whatever adjustments you see near the laser, those are not related at all to the issue you described. So, best "don't touch that dial" and see if you can get replacement belt of the proper size.

IMO, o-rings work fine for this purpose but have to be handpicked for proper size and length. You may grab a few sizes that resemble your belt. Make sure to wipe them with alcohol to remove all lubrication, as they sometimes come pre-lubed.
 
Success with Square Belt, but not with O-ring

For my C541, I purchased a square belt from MCM, and it works great. I used MCM's instructions for measuring and calculating a suitable replacement.

http://www.mcmelectronics.com/product/42-120

I tried the #29 Danco O-ring first, but it made the tray very very slow and sometimes the tray still wouldn't open. The O-ring is much thicker and less stretchy than the square belt.

I also put a very tiny amount of white lithium grease (available at Lowes) on all the moving parts - not certain, but that appears to be what what used originally.
 
How funny is this? I'd completely forgotten about this thread and yesterday I found Bart's youtube video on the repair! I only dug this thread up because I wanted to post the link :D
(the commentary is Dutch only but you can see where all the components are)
https://www.youtube.com/watch?v=FvKKLh4oTis

Just one question:
I'm trying to figure out the relation between Zener voltage and input/output voltage according to the Sanyo datasheet.
http://pdf1.alldatasheet.com/datasheet-pdf/view/40488/SANYO/LB1641.html
The NAD sends 8 V to the LB1641, so how would the Zener voltage influence that? According to the graph at 18 V input voltage the output voltage equals the Zener voltage up to 16 V. Would that be the case for 8 V input as well? If so I'd probably try a 4.3 V diode instead. BTW, did you measure the original resistor whether it had drifted?

Oh and another question: did you replace the electrolytics with 105° C ones? It'd seem wise considering how close they are to the voltage regulators (in my unit one of the caps in the audio power supply section is actually glued to a heatsink!).
 
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EDIT: Important new info posted here.
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EDIT 2: This exact model NAD C541 has Sanyo laser SF-P101N 15-pin version. There is a 16-pin version of the same laser that does not work in NAD C541!
The whole brand new laser assembly with two motors, is less than $20 on ebay, just make sure to get the 15-pin version of Sanyo SF-P101N. Replacement procedure is realatively easy. No adjustments.
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This NAD C 541 HDCD player is my latest acquisition off CL. Cost me $25 with remote and original box.

This is a nice-sounding HDCD machine, positively reviewed here and here. Original price tag in 2000 AD was $500.

But…. Tray won't open, though you hear the motor whining.

Google says that this is a common problem for this CD player, so I'm posting details of my repair. Basic skills, common sense, steady hands, 59 cents o-ring and a Philips #2 screwdriver required for the fix.

Disconnect the power cable! 5 screws hold the outer case - take it off.

Remove 4 elevated screws in the bottom - they hold the black plastic transport assembly.

While removing the last of the four screws, don't forget the ruthless Laws of Gravity - make sure the transport doesn't drop ripping the ribbon cables with it.

Never, at any point, use excessive force in this repair.


28873566.jpg

To remove the transport completely lift the back of it (like in the picture) and at the same time try to slide off the front plate of the tray. The oval decorative plate slides off upwards. You need to remove the plate to free the transport assembly completely and to gain access to the innards of the tray's motor, belt and pulleys.


81073916.jpg

Notice two sets of cables and a ribbon running to the assembly. My recommendation is to leave them connected, but be extra gentle when flipping parts around, and keep the flipping to a minimum.


83755625.jpg

Directly under the front part of the tray (when it's closed) there is a black plastic toothed gear - turn it with your finger to set the tray in motion, then move tray all the way out. Notice two little plastic tabs on the top of the tray - press them both outward and the tray can be removed. Now you see the motor and the rubber belt that became stiff and slack.


oringe.jpg

I did not have a proper replacement belt, which should be square. I went to Ace hardware, to plumbing section and got a couple of different size o-rings for 59 cents apiece, hoping that one of them would work. And indeed! O-ring #29 works great.

The o-ring felt greasy out of the bag. It may have been treated with silicone grease. Wipe it with rubbing alcohol, and wipe it good! Then install.

This belt works only when the tray is operated, so it should stay healthy for a long time.

O-rings are made of very durable material:

oringt.jpg
Terrific idea. I went to local DIY & bought a O ring (2 pack) for £1.47. Works a treat and it's the first time the CD player has been working properly since I got off ebay 10 years ago
 
I just fixed my broken NAD C 541 by following the advice on this thread.

For D701 I used a 1/2 watt 6.2V Zener diode (1N5234, Mouser Part No. 78-1N5234B-TAP). It is not that hard to remove the main board to solder this properly in place. Remove the small ribbon-ish cable in the front right of the board, the screws holding the board to the tabs on the sides of the case and the stand-offs, and the screws holding in the RCA jacks in the back. (Only that one wire-to-board connector needs to be removed, and it just unplugs---no desoldering.) The board can then be lifted up with some care---it is just a little tricky to get the RCA jacks pushed up over the rear of the case. You can get it pretty much vertical to the point where desoldering and soldering should be trivial.

After doing this, the CD tray would slide in and out perfectly (before it took like 10 seconds to go in or out...), but the CD would still not push up into place.

So, onto the belt/O-ring: you can access that WITHOUT TAKING ANYTHING APART. Just push the CD tray forward a bit and you can take that belt out with some tweezers and needle-nose pliers. (It is plainly visible just behind the front panel when the tray is open.) I bought a bunch of different O-rings, but none of them fit anywhere near as well as the original belt. I just cleaned it with isopropanol, and also cleaned the larger wheel where it mounts. Dip a Q-tip in the IPA and hold it against the wheel while sliding the tray back and forth. Get all that damn grease off that stuff! I think the grease migrates from the little gear just to the left of the larger wheel, where it probably SHOULD be present...

#29 as an O-ring size seems a little ambiguous. Certainly the width should be 1/16" so it will have a bit of elasticity (3/32" is too rigid). One website I visited says the inside diameter (ID) of a #29 O-ring should be 1+1/2", but at the hardware store the #29 he showed me was a lot smaller... maybe only 1" ID. I didn't buy the smaller one, but instead had him sell me a larger size, which was probably a mistake. Anyway, probably the correct O-ring has an ID of 1" or perhaps a bit more... I'd buy 1" and any larger sizes they had available if I did it again, but, like I said, cleaning the original belt worked fine for me.
 
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