My NAD C540 is having serious skipping problems.
The skipping depends from cd to cd, for example one of my 16 track discs plays fine, but my 20 track Jimi Hendrix compilation disc skips like hell.
I noticed the 7808 voltage regulator gets very hot (> 50° C). Is this normal?
The NAD already has the 'capacitor mod', so that's not the problem.
I have tried adjusting the only adjustment pot on the optical assembly, and it changes things but it does not solve them completely.
I need the service manual to adjust it to factory specs. Does anybody have the service manual of the NAD C540?
Are there people with the same problems? I don't want to give up on it, because some of my cds play perfectly fine and sound really nice...
The skipping depends from cd to cd, for example one of my 16 track discs plays fine, but my 20 track Jimi Hendrix compilation disc skips like hell.
I noticed the 7808 voltage regulator gets very hot (> 50° C). Is this normal?
The NAD already has the 'capacitor mod', so that's not the problem.
I have tried adjusting the only adjustment pot on the optical assembly, and it changes things but it does not solve them completely.
I need the service manual to adjust it to factory specs. Does anybody have the service manual of the NAD C540?
Are there people with the same problems? I don't want to give up on it, because some of my cds play perfectly fine and sound really nice...
The c540 is a nice sounding player but they do have a problem with skiping i bought one new when they first came out in 2000 it went back to nad 3 times and was never cured i replaced it at the end of the 2 year warenty for a diferent make and still have the player and it still never skips 12 years on i was lucky if my nad played a cd at all without skipping even brnd new discs :-(
That's such a shame. Why would they take all these good components and then put a shitty transport in it? It doesn't make sense...
Nobody has the service manual?
Nobody has the service manual?
Didn't have much luck finding a manual either, but those regulators run pretty warm on many CDPs on which I've worked.
That sounds like the APC preset (laser automatic power control). If you altered that and with no means of reference to reset back (such as a known RF level on a scope or noting the laser current) then all bets are off I'm afraid.
(regulators in much commercial stuff can run very hot indeed. 50C is nothing to be concerned over)
Doing that can certainly help keep temperatures on the board down, beneficial for caps and the pcb itself.
Not a big fan letting things get "hot".
I'm wondering if there'd be any benefit to using a higher amperage device in its place...
I'm wondering if there'd be any benefit to using a higher amperage device in its place...
No benefit at all unless you went for a different package with more surface area. The power dissipation is the same no matter what the regulator rating is (same current flows and the same voltage is lost across the reg = same power = same heat)
Thanks for all the replies!
I marked the original position on the potmeter I adjusted, so I can put it back to its original position. Problem is, skipping get MUCH worse when I do that.
I know regulators can get quite hot, but in this NAD there are actually black heat stains above the regulator, and the psu caps are right next to the heat sink @50-55°C. I still need to check the power supply ripple with a scope, but can dried out caps (excessive ripple) be the cause of the skipping problem?
not my pic:
I marked the original position on the potmeter I adjusted, so I can put it back to its original position. Problem is, skipping get MUCH worse when I do that.
I know regulators can get quite hot, but in this NAD there are actually black heat stains above the regulator, and the psu caps are right next to the heat sink @50-55°C. I still need to check the power supply ripple with a scope, but can dried out caps (excessive ripple) be the cause of the skipping problem?
not my pic:
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In absolute terms 55C is well within limits for the regs and caps, but yes, heat shortens the caps life. From what you describe the caps probably wouldn't be the first suspect but it would be good to check the ripple on them and perhaps replace them with 105C specified parts as part of the repair. The reg would stop ripple appearing in the output unless any dried out cap were in front of the reg (the larger reservoir caps)
If altering the laser power back to original makes it worse then that really points to a faulty pickup. If you have a scope you need to look at the quality and level of the RF signal from the pickup. Typically its around 1.2 to 1.5 volts pk/pk.
Stains on the regs could be just convected heat drawing atmospheric pollution up and over them. There is nothing obviously untoward in the picture as far as its possible to make out.
If altering the laser power back to original makes it worse then that really points to a faulty pickup. If you have a scope you need to look at the quality and level of the RF signal from the pickup. Typically its around 1.2 to 1.5 volts pk/pk.
Stains on the regs could be just convected heat drawing atmospheric pollution up and over them. There is nothing obviously untoward in the picture as far as its possible to make out.
The stains are on the inside of the cover plate (not on the pic 😉 )
I'll check the RF signal with my scope tomorrow or next week. It seems replacement pickups aren't that expensive, so I might give that a try.
New Original Sanyo Laser Lens SF P101N 5P 8P 5 8 Pin Optical Pick UPS | eBay
Absolutely normal to see discolouration of cabinet tops and so on. No problems there.
Yes, if you have a scope then give the RF a look as that is the biggest guide of all really. It should look as good as in these pictures, any jitteriness or poorly distinguished diamond pattern are all problems
http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html
Yes, if you have a scope then give the RF a look as that is the biggest guide of all really. It should look as good as in these pictures, any jitteriness or poorly distinguished diamond pattern are all problems
http://www.diyaudio.com/forums/digital-source/226288-sony-cdp790-kss240-restoration-project.html
Okay, I did some measurements.
The power supply ripple is very low. This can't be a problem. So i decided to check the eye pattern. Without a service manual, I did not know where the RF test point was. I think I found it, however. This was the only signal of it's kind present at the board.
First: My scope is a HP 54501 Digital scope (100Mhz). It is very old but it was totl back then (early 90s). I read somewhere that it is difficult to capture an eye pattern with a digital scope. I don't know if this is true???
Settings on the scope: 500ns/div, 0.5V/div. triggered on rising edge @ 0.0V.
It doesn't look good at all.
This is at the very beginning of the CD, paused right at 0:00.
Same, triggered on falling edge.
This is everywhere else on the cd (paused looks the same). Notice how it looks much worse.
Same, but now clocked on a rising edge @ -250mV
These are single trigger shots. Notice how the amplitudes aren't the same and how the sine wave is distorted.
I have tried to adjust the laser. I can adjust it so the eye pattern doesn't clip. I can't get the eye pattern to look clean, however.
Assuming my measurements were right:
To me it seems that the timing is just way off.
The power supply ripple is very low. This can't be a problem. So i decided to check the eye pattern. Without a service manual, I did not know where the RF test point was. I think I found it, however. This was the only signal of it's kind present at the board.
First: My scope is a HP 54501 Digital scope (100Mhz). It is very old but it was totl back then (early 90s). I read somewhere that it is difficult to capture an eye pattern with a digital scope. I don't know if this is true???
Settings on the scope: 500ns/div, 0.5V/div. triggered on rising edge @ 0.0V.
It doesn't look good at all.
This is at the very beginning of the CD, paused right at 0:00.
Same, triggered on falling edge.
This is everywhere else on the cd (paused looks the same). Notice how it looks much worse.
Same, but now clocked on a rising edge @ -250mV
These are single trigger shots. Notice how the amplitudes aren't the same and how the sine wave is distorted.
I have tried to adjust the laser. I can adjust it so the eye pattern doesn't clip. I can't get the eye pattern to look clean, however.
Assuming my measurements were right:
To me it seems that the timing is just way off.
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That doesn't look good but like you, I suspect the scope. Tbh its the best shot of the RF on a digital I've seen on here. All those artifacts are going to be down to the scope sampling I imagine.
To actually measure the RF you just need play any standard pressed disc. Any disc no matter what the content will always look the same.
I think you are probably looking at a replacement pickup here.
To actually measure the RF you just need play any standard pressed disc. Any disc no matter what the content will always look the same.
I think you are probably looking at a replacement pickup here.
Replacement pickup seems reasonable.
I have one more question: are those ebay 'original pickups' geniune? On the original, there's a Sanyo logo on top of the pickup, I don't see that on the pickups for sale on ebay.
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I have one more question: are those ebay 'original pickups' geniune? On the original, there's a Sanyo logo on top of the pickup, I don't see that on the pickups for sale on ebay.
That I'm afraid I can not answer. Philips CDM 12xx type are well known for being poor quality non originals but I've not heard anything regarding these. There are many "generic" replacements around for the likes of the common Sony KSSxxx types and these are generally fine.
So I would say a fair chance its fine.
If you look here (if the link works) you will see all the different prices on offer,
Search results for SF-P101N
If the link is no good search for it here,
CHS - replacement remote controls, instruction manuals, audio & video accessories, electronic components & spare parts
So I would say a fair chance its fine.
If you look here (if the link works) you will see all the different prices on offer,
Search results for SF-P101N
If the link is no good search for it here,
CHS - replacement remote controls, instruction manuals, audio & video accessories, electronic components & spare parts
Attachments
You will see the cheapest one in those above is described as "copy" but that is what a service dept would order and fit as a general rule.
I had to wait a LOOONG time, but finally, my new laser has arrived!
I can definitely see this one is much, much brighter than the old one.
It plays most cds fine now, even my most 'difficult' 20 track (4 tracks over spec) Jimi Hendrix cd. But, I heard a few skips when trying a burned cd.
I think it has to be calibrated, but this would mean checking the eye-pattern again and adjusting the laser current. My finals start in 2 weeks, so that will have to wait 🙂
Thanks for the help!
I can definitely see this one is much, much brighter than the old one.
It plays most cds fine now, even my most 'difficult' 20 track (4 tracks over spec) Jimi Hendrix cd. But, I heard a few skips when trying a burned cd.
I think it has to be calibrated, but this would mean checking the eye-pattern again and adjusting the laser current. My finals start in 2 weeks, so that will have to wait 🙂
Thanks for the help!
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