What can cause a CD-player to suddenly create white noise instead of music?
That's the problem I had (I hope) with my Primare D20. This player is about 10 years old now. It's the model with the Philips CDM12.4 mechanism (I believe the later version of the D20 had a Sony mechanism).
The problem started to appear when it was 4 or 5 years old. Once in a while the player would suddenly put a noise that can only be described as white noise on the analogue output (not on the S/PDIF output, though). It could happen 5 mins after switching on or after a hour or so. Once the white noise started, it would go on forever. The only way to get it back to normal operating condition was to power it down completely and switch it back on (it also has stand-by mode), but then it was just a matter of time before the white noise would reappear.
After a while it got so bad that I decided to have it repaired. The DAC-board (AK4324 DAC and OPA132s opamps, muting relay) was replaced and everything seemed fine...sadly only for a few months... I put it away for several years and I recently decided to try to bring it back to life myself.
Since the DAC board had already been replaced with a new item, I assumed the error had to be somewhere else, so I took out the mechanism to have access to the main board which sits beneath it. On it were some marginally soldered ICs and some (factory fitted) modifications that looked messy. I took out the pcb and took it to work where I have access to excellent rework equipment (forget Weller, go JBC). I took off some ICs and put them back on properly and tidied up some mods (esp. a resistor-mod on the SAA7xxx (I forget) which was sitting incredibly close to a capacitor and a pin)).
The player worked fine for some days, but then....the white noise came back. There was only one thing left, and that was to take out the (low cost) socket and solder a ROM IC directly on the board. The IC I'm talking about is the ROM for a 80C32 microcontroller. That seems to have done the trick, although I'm not sure yet. If the D20 keeps behaving well for a few more days, I will pronounce it repaired.
In the meantime I wonder what would have caused a DAC to spit out white noise... Any ideas???
That's the problem I had (I hope) with my Primare D20. This player is about 10 years old now. It's the model with the Philips CDM12.4 mechanism (I believe the later version of the D20 had a Sony mechanism).
The problem started to appear when it was 4 or 5 years old. Once in a while the player would suddenly put a noise that can only be described as white noise on the analogue output (not on the S/PDIF output, though). It could happen 5 mins after switching on or after a hour or so. Once the white noise started, it would go on forever. The only way to get it back to normal operating condition was to power it down completely and switch it back on (it also has stand-by mode), but then it was just a matter of time before the white noise would reappear.
After a while it got so bad that I decided to have it repaired. The DAC-board (AK4324 DAC and OPA132s opamps, muting relay) was replaced and everything seemed fine...sadly only for a few months... I put it away for several years and I recently decided to try to bring it back to life myself.
Since the DAC board had already been replaced with a new item, I assumed the error had to be somewhere else, so I took out the mechanism to have access to the main board which sits beneath it. On it were some marginally soldered ICs and some (factory fitted) modifications that looked messy. I took out the pcb and took it to work where I have access to excellent rework equipment (forget Weller, go JBC). I took off some ICs and put them back on properly and tidied up some mods (esp. a resistor-mod on the SAA7xxx (I forget) which was sitting incredibly close to a capacitor and a pin)).
The player worked fine for some days, but then....the white noise came back. There was only one thing left, and that was to take out the (low cost) socket and solder a ROM IC directly on the board. The IC I'm talking about is the ROM for a 80C32 microcontroller. That seems to have done the trick, although I'm not sure yet. If the D20 keeps behaving well for a few more days, I will pronounce it repaired.
In the meantime I wonder what would have caused a DAC to spit out white noise... Any ideas???
Sounds like a logic "lockup" to me. It's the sort of symptom you can create by shorting out random IC pins etc ( not something you should do unless you are extremely bored and don't mind the possible consequencies ) and the unit stays locked up until you switch off. Bit like a computer not responding etc.
As to a specific cause it could be anything !! Anything that gets hot, such as a regulator developing dry joints and "spiking" the logic is a possible, it really could be anything though. You may well have found the cause with the socket - time will tell
As to a specific cause it could be anything !! Anything that gets hot, such as a regulator developing dry joints and "spiking" the logic is a possible, it really could be anything though. You may well have found the cause with the socket - time will tell
Thanx for the input. Right now I'm listening to music played by the D20, so it's still behaving very well! It has been playing perfectly for longer than ever since the problem appeared for the first time. I rediscovered why I had bought this player despite the fact that it was priced quite a bit higher than the max I had in mind at the time...
The theory I have now is that the serial audio data going to the DAC board at some point got so corrupted that it no longer made any sense. It was not a complete lock up of the player because it still played discs and responded to the controls af if everything was fine. If memory serves me right even the digital output still fucntioned correctly when the analogue outputs were creating white noise...
The theory I have now is that the serial audio data going to the DAC board at some point got so corrupted that it no longer made any sense. It was not a complete lock up of the player because it still played discs and responded to the controls af if everything was fine. If memory serves me right even the digital output still fucntioned correctly when the analogue outputs were creating white noise...
Steerpike said:
In my case, it's not the DAC I was worried about. Yes, at first I thought about the DAC too, and so did the technician who replaced the DAC-board. As I wrote in the start of this topic, it did not cure the problem, though. The fact that the S/PDIF output did not suffer from the white noise problem leads me to believe that there's something in the digital audio path between the point where that signal is taken and the DAC and that it's somewhere between these two points the problem occurred.
When looking at the layout of my other CD-player (Nakamichi CD-4), it seems to me that the S/PDIF signal is NOT routed through the digital filter. Can anyone shed some light on this?
When I load a CD-ROM, the player says " NO DISC" in the display but when I press the play button it will start to play anyway. The sound I then hear does not sound the same as the white noise I experienced. Playing a CD-ROM sounds far more agressive data-pattern-like.
One thing I had not mentioned yet was that it could also start to produce white noise in stand-by mode! Apparently the D20 doesn't mute the analogue output in stand-by mode...
, the white noise came back today. I'm running out of possible causes.Everytime I tried something (meaning the disconnection and removal of the mechanism and mainboard), the white noise would stay away for a while. That's why I'm now thinking it may be caused by a connection going bad after a while.
DAC-board of the Primare D20 CD-player
As you can see there is a flatcable between the DAC-board and the mainboard. The boxed headers and connectors are not gold-plated. How likely is it that this kind of connection turns bad after a while (oxidation)?
Well, I think I'm going to replace the whole thing with seperate strands that I solder directly onto those boards.
I might even use thin coax cables because I noticed the flatcable picks up some hum when I turn up the volume on the amp to the max. If I wrap some aluminium foil around the flatcable, the hum is nearly gone...
I might even use thin coax cables because I noticed the flatcable picks up some hum when I turn up the volume on the amp to the max. If I wrap some aluminium foil around the flatcable, the hum is nearly gone...
What do you mean by DJ's? Dry joints?
If so, yes PSU is fine.
Digital and analogue circuits in the D20 have separate PSUs, starting with two transformers. The DAC-board has its own PSUs (it gets AC power from the transformers), again digital and analogue are separated.
One of the first things I did was measure the PSUs and the oscillator. All are rock steady.
If so, yes PSU is fine.
Digital and analogue circuits in the D20 have separate PSUs, starting with two transformers. The DAC-board has its own PSUs (it gets AC power from the transformers), again digital and analogue are separated.
One of the first things I did was measure the PSUs and the oscillator. All are rock steady.
Dry joints yes It sounds a tricky one this. By their very nature "digital" faults once they occur don't usually go back to normal again unless the logic is reset by powering off which makes fault finding all the more difficult.
It's usually things that run hot that suffer with DJ's but not always. If the transformers are PCB mounted it's worth running an iron over them. Any fuse holders ? When you do find it you will kick yourself, the evidence will have been there all along.
If you suspect an IC try a hairdryer on it to heat it up while it's on. Give everything a good poke, again while it is on.
Good luck
It sounds a tricky one this. By their very nature "digital" faults once they occur don't usually go back to normal again unless the logic is reset by powering off which makes fault finding all the more difficult. It's usually things that run hot that suffer with DJ's but not always. If the transformers are PCB mounted it's worth running an iron over them. Any fuse holders ? When you do find it you will kick yourself, the evidence will have been there all along.
If you suspect an IC try a hairdryer on it to heat it up while it's on. Give everything a good poke, again while it is on.
Good luck
Mooly said:
They are and I resoldered them today, just to make sure.
Only one in the primary side, the others (SMD) are soldered directly onto the mainboard.
If you suspect an IC try a hairdryer on it to heat it up while it's on. Give everything a good poke, again while it is on.
Good luck
That will only be possible with ICs on the DAC-board. The ICs on the mainboard are almost completely hidden below the mechanism. I don't suspect any of them though.
This evening I replaced the ribbon cable by bits of standard (shielded) interlink cable. It was a time consuming and fiddly mod, and the only thing to do now is listen to music and be patient...
EDIT: This time I didn't have to wait for very long...it's spitting out white noise again...
Try extremely small amounts of freezer spray on any suspect IC with it working. I say that because once it does it's fault there is a good chance that even if the IC was playing up it would have "confused" the logic and blasting it with freezer may not correct it. The idea is to see if you can keep it from going faulty. Just drip freezer onto the part every minute or two.
Well, the freeze spray (FS) is something I hadn't considered yet, even though at work I sometimes use it too for finding a fault. It's something I can't try yet though, I have no FS handy...
I kept myself busy with the D20 anyway. It's a nicely designed CD-player with one exception: the PCB-mounted transformers. From the very beginning I had plans to move them off-PCB because they put out a loud mechanical hum which the 2 mm thick steel housing only seems to amplify (resonance frequency?). Despite this, the D20 has always been a very musical player. Whatever I play, I can't stop tapping my feet, with the exception of the many "loudness war" CDs record companies are putting out nowadays.
This mod might sound a little off topic, but yesterday the white noise came back far more rapidly than usual after trying something. This morning I found out that I hadn't tightened the screw that sits between the (digital) transformer and the two elcos. That got me thinking: what if the vibrations have something to do with the white noise fault??? Only one way to find out: apply the mod I always wanted to do, but somehow never did, until now.
As you can see, the mechanical hum has been taken care of. The transformers now sit upside down on some soft rubber rings. The D20 is no longer a "hummingbird".
I also reverted to the ribbon cable between the DAC-board and the mainboard. Three reasons: it was not the cause of the white noise, the D20 sounded more clinical with the interlink-wiring and it looks far less messy this way.
The hum in the analogue signal (in the noise floor) at very high volume levels has also been reduced to nearly nothing by the longer distance between the DAC-board and the transformers.
But will the white noise problem come back or not? Time will tell...
I kept myself busy with the D20 anyway. It's a nicely designed CD-player with one exception: the PCB-mounted transformers. From the very beginning I had plans to move them off-PCB because they put out a loud mechanical hum which the 2 mm thick steel housing only seems to amplify (resonance frequency?). Despite this, the D20 has always been a very musical player. Whatever I play, I can't stop tapping my feet, with the exception of the many "loudness war" CDs record companies are putting out nowadays.
This mod might sound a little off topic, but yesterday the white noise came back far more rapidly than usual after trying something. This morning I found out that I hadn't tightened the screw that sits between the (digital) transformer and the two elcos. That got me thinking: what if the vibrations have something to do with the white noise fault??? Only one way to find out: apply the mod I always wanted to do, but somehow never did, until now.
An externally hosted image should be here but it was not working when we last tested it.
As you can see, the mechanical hum has been taken care of. The transformers now sit upside down on some soft rubber rings. The D20 is no longer a "hummingbird".
I also reverted to the ribbon cable between the DAC-board and the mainboard. Three reasons: it was not the cause of the white noise, the D20 sounded more clinical with the interlink-wiring and it looks far less messy this way.
The hum in the analogue signal (in the noise floor) at very high volume levels has also been reduced to nearly nothing by the longer distance between the DAC-board and the transformers.
But will the white noise problem come back or not? Time will tell...
Definitely not physical ? Poking and bending the PCB's has no effect at all does it ?
Very strange fault. In all the years I worked on CD players I have vague recollections of only one ROM failure, I don't think it was intermittant though. Must be nearly 20 years ago now
LSI chips are usually supremely reliable. You will have to see.
Very strange fault. In all the years I worked on CD players I have vague recollections of only one ROM failure, I don't think it was intermittant though. Must be nearly 20 years ago now
LSI chips are usually supremely reliable. You will have to see.
In 8+ years I've had my share of bad connections, esp. in multilayer PCBs, although it's not a common phenomenon. Cracked ceramic capacitors can sometimes also be found by bending or pressing.
So yes, I applied the trick while the D20 was playing, it doesn't seem to affect it though.
While removing the transformers I seriously stressed the main PCB. Lets just say that they were hell to remove, but I managed without any (serious) damage. If there is/was an intermittent contact, it may have been repaired in the process for now or forever (preferably the latter).
I'm not thinking the ROM was the cause anymore. The D20 is operable when the white noise appears and yesterday I confirmed that the S/DIF output was working fine while at the same time the analogue output was nothing but white noise.
Contrary to what I wrote, the boxed headers for the ribbon cable are gold-plated.
So yes, I applied the trick while the D20 was playing, it doesn't seem to affect it though.
While removing the transformers I seriously stressed the main PCB. Lets just say that they were hell to remove, but I managed without any (serious) damage. If there is/was an intermittent contact, it may have been repaired in the process for now or forever (preferably the latter).
I'm not thinking the ROM was the cause anymore. The D20 is operable when the white noise appears and yesterday I confirmed that the S/DIF output was working fine while at the same time the analogue output was nothing but white noise.
Contrary to what I wrote, the boxed headers for the ribbon cable are gold-plated.
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