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Old 22nd April 2003, 03:08 AM   #1
Nicwix is offline Nicwix  Australia
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Default Strange problem with Marantz CD-74

Hi

I bought an old Marantz CD-74 CD Player (built like a tank) that has a very distinctive problem. bawling: I am sure if I describe the symptons, someone will be able to give me a pointer to fixing it.:

The machine plays discs, but the music is accompanied by a scratchy, crackling like distortion in both channels - almost like static. Amazingly, the crackles are exactly identical every time at a given point on a track - that seems to indicate it must be a digital problem.

Both channels are affected (even though the machine has separate DACs (2 x TDA1540) and separate analogue sections. PSU measures OK.

Volume of the crackling is similar to the maximum level of the music. The crackling is definitely linked to the music, but not in an obvious way (ie does not appear to worsen with volume).

Other key chips in this machine are:
SAA7010 - ?
SAA7020 - Phillips CD error correction chip
SAA7030 - Philips digital filter chip

Any help appreciated
Nic
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Old 22nd April 2003, 07:04 AM   #2
Netlist is offline Netlist  Belgium
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Default Re: Strange problem with Marantz CD-74

Quote:
Originally posted by Nicwix
the crackles are exactly identical every time at a given point on a track
Hi, Nicwix
What do you mean by this?
Are the crackles there all the time and only identical at specific moment in time of a track?
What do you mean by 'identical'?
Are the crackles synchronic with the speed of the disk?
On every track of every CD?
Is there mechanical noise from the player when volume is turned down?

Quote:
Volume of the crackling is similar to the maximum level of the music.
So even in very silent peaces of music, the crackle is always at the same (max) volume? Or does it vary with the dynamics?

Quote:
Both channels are affected
Then the problem will probably not be found in the separate sections.

Is there a remote control cable attached?

/Hugo
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Old 22nd April 2003, 08:13 AM   #3
Nicwix is offline Nicwix  Australia
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Default Re: Re: Strange problem with Marantz CD-74

Quote:
Originally posted by Netlist
... What do you mean by 'identical'?
The crackles sound random - like static (or distant lightning) on an AM radio - but if I listen repeated to the same section of a track, then exactly the same crackles occur.

Quote:
... Are the crackles synchronic with the speed of the disk?
No, the crackles sound random - no repetitive nature at all

Quote:
On every track of every CD?
Yes

Quote:
On every track of every CD?
Is there mechanical noise from the player when volume is turned down?
Some mechanical noise, but I can't identify any correlation with the crackles

Quote:
So even in very silent peaces of music, the crackle is always at the same (max) volume? Or does it vary with the dynamics?
Crackle is same volume, regardless of music volume - it does stop when CD is on pause or stopped

Quote:
Then the problem will probably not be found in the separate sections.
???

Quote:
Is there a remote control cable attached?
There is provision for a cable remote, but none attached

So what does that all mean???
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Old 22nd April 2003, 08:54 AM   #4
Netlist is offline Netlist  Belgium
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Nicwix,

Look if the SAA's are well seated in their sockets, if any.

Try warming up the SAA's. A hairdryer might work, but a soldering iron at close distance is better. Don't make them to warm of course.
If you can, try to freeze them with cold spray too. But be careful with that. Apply just a tiny bit of cold spray. Too cold might ruin the SAA's.

Listen if there is any difference.
If any, you got the correct SAA.
Never mind the remote control cable if not attached.

The SAA7010 is a Demodulator, Drop Out Detector
The SAA7020 is an error corrector
The SAA7030 is stereo Digital Filter

Found this on the net too:

Quote:
Crackle / static and high frequency whine seemed to be associated with the LM337T
-ve regulator as again broken soldering in this area. But with 0V (contact break) on the output no static
and -7V o/p return of crackle. Probably due to bad seating of SAA7030 in socket.
Data on these old Mullard /Philips CD SAA7000 series ICs (probably manufactured
in Southampton) in Signetics 1984 Linear LSI manual.
This means you should check the PSU for bad solderings too.

/Hugo
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Old 22nd April 2003, 10:25 PM   #5
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Had this problem before with TDA1540's. They were worn out ! These DAC's have this problem after years of use.

Once I heard a Cambridge cdplayer that crackled the first minutes and after warming up it played without the crackling. According to the manufacturer replacing the DAC chips would solve the problem which I didn't do because of the high cost at that time.

Maybe you can make a small PCB for TDA1541/1543 if the player has I2S ?
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Old 30th April 2003, 12:39 PM   #6
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Faced a similar problem with my CD63SE.
Got the noise you described.
A few transistors on the RF board were busted.
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