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-   -   Kenwood DP-4020 CD Player woes (http://www.diyaudio.com/forums/digital-source/224755-kenwood-dp-4020-cd-player-woes.html)

JesseG 1st December 2012 07:00 PM

Kenwood DP-4020 CD Player woes
 
Hi all
I have an older Kenwood DP-4020 in quite nice shape. At least I think it is worth saving. It is producing static (yes, static) mixed in with the music.
This is not a hum or buzz, but random static - like a poorly tuned radio station.

I have replaced the output op-amp, but no improvement.

Is anyone out there familliar with this player or maybe has a service manual?
For that matter, has anyone come across this symptom in a CDP?

Help, as allways, is deeply appreciated :)

Jess

stephensank 2nd December 2012 06:32 PM

I have never seen a PCM1700 dac chip go bad in any way, but there is a first time for everything. Otherwise, if the static seems to follow disc rotation speed, it is almost certainly either a platter motor bogging down, or a bad error correction RAM chip. If it's entirely random, and not the dac, it would most likely be a bad signal proc chip. The other possibility, not at all remote, is that there are electrolytic caps dying in the sig proc &/or dac areas, or in supply.

JesseG 3rd December 2012 04:02 AM

Thanks Stephen. with so many possibles, I am thinking that the way to trace this puppy is to record a simple sine wave onto a CD and then start working backward from the output jacks to the DAC. That is, if it is being generated in the audio stages.

Is it even possible for noise of this type to be generated somewhere in the digital circuitry?

Nanook 4th December 2012 02:03 PM

Static charge/discharge
 
Hi Jesse.
Although I am far from being a tech...

... I'd suggest the output caps on the output stage and/or power supply. Not much help, and only a guess, but a reasonable suggestion I think.

JesseG 6th December 2012 02:25 AM

Yeah, thnaks Stew. I am planning to put it on the scope this weekend and see what I can see.

Mooly 6th December 2012 07:14 AM

Stephens suggestions above are sound.

Also if the signal from the pickup is marginal then it is possible to get this effect. Does the problem alter at all if the player is stood on end/upside down while playing ? If so then the problem could well be mechanical/pickup related.

JesseG 7th December 2012 08:46 PM

Thanks all - I have some things to test :D


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