whining kss210A after replacement

[willos]

Hi,

I am new to this forum and thus far, though I searched tis forum, I seem not to be able to find a solution to my problem. Sorry if I'm asking a question that has been answered somewhere.
After replacing the KSS210A laser unit in my Denon DCD1420 I am able to play CDs, but there is an annoying whining, which seems to stem rom the laser unit and after sone time the CD player goes berserk.
Anyone ideas on what this might be, or what I can do about it?

Thanks
Willem

[Mooly]

It needs setting up. Is there a focus bias pot ? on the main PCB. If any pots have been tweaked a full alignment is in order. Focus bias you can tweak, don't touch anything else without a scope and manual.

[willos]

Thank you! There are five pots on he mainboard: TR.GAIN, TR.OFFSET, F0.GAIN. F0.OFFSET and PLL.ADJ. Which one do I have to tweak?No pots have been touched so far.

Best, Regards,
Willem

[Mooly]

Do you have an oscilloscope ? That's the only sure way to see what's going on, however,
Mark all the pots with a felt marker first, it's so easy to turn something by mistake.
Tracking gain and focus gain are surprisingly uncritical---- do not alter these yet. PLL critical adjustment but is not related to the pickup -- don't touch.
Tweak the Focus offset pot while it is playing. Set it where the "white" noise from the pickup is minimum. See what that does and report back.

Non of these pots will do any damage if they are turned incorrectly.

[willos]

Thanks again. I will try that tonight.

Willem

[willos]

Yes!!! You are great! That did the job. I turned the FO.OFFSET slowly for about 20 degrees and heard the wining disappear.
Thank you very, very much!

I take it there's nothing left to be done?

Thanks again,
best regards.
Willem

[willos]

Well... that is... I'm afraid I have been reacting too soon...The whining is gone, but still there appear to be tracking problems: the player 'hangs' and stutters when approximately half way the disk. Maybe this can be taken care of by one of the other pots?

[kevinkr]

Make sure there is no mechanical binding in the sled drive mechanism before adjusting anything else..

Those pots really have nothing to do with the sled's travel during the course of play.

I am also assuming this occurs with all disks and not just one specifically.

[anatech]

Hi Willem,
Sounds like a defective head. When you turned the gain down, it was reduced too far. Return the control to the original position. You need another KSS-210A head.

Whatever you do, do not turn any more controls. You absolutely do require a 'scope to set these machines up. There is even a program built into the machine to make things easier. Since your machine is a really nice one, did you consider getting the service manual for it?

There is a clamp arm modification, I wonder if that's been done? The original is a pressure clamp system, the revised type is a magnetic clamp system. The arm decouples from the "puck" that holds the CD down on the turntable. There are other mods, but the arm change is normally done at the same time. Last I heard, those parts have been discontinued.

The E-F balance control setting is critical. Do not touch it unless you know exactly what you are doing.

If the arm modification has been done, this is an excellent player and well worth keeping. I would find a good audio technician who has a good reputation set this machine up. Look for a Denon warranty shop.

-Chris

[Mooly]

Hi Willos,
As Anatech mentioned a 'scope is the only sure way to see whats happening.
The focus offset ( or bias ) adjustment on it's own is do-able, the point of minimum noise from the pickup should coincide with the correct setting. I used to find this time and again -- I alway use a scope but setting by ear ( I can see Chris cringeing at that - sorry Chris ) was, with experience just as good. For that one adjustment only I must add.
You mention the problem of sticking half way through the disc. That points to a mechanical issue really, maybe some gunge in the teeth of the sled motor or the rack on the pickup.
I would recheck the setting on that pot, turn it up to the point where the noise is just becoming audible and then back it off a degree or two.
Is there an EF balance pot ?? You didn't mention it at first- some players don't have the adjustment anyway- but as Anatech says that adjustment is super critical and a scope is definitely required for that one.
The one pot not to turn is the one on the pickup, the laser power.
Why did you replace the pickup anyway -- was it for the sticking problem ?