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Denon DP 60 L running slow

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Denon DP 60 L running slow

Postby jvsantosmd » 26 Nov 2017 18:13

I had my unit serviced, it arrived and performed flawlessly for about 15 min, then began running slow. The repair shop led me to remove the platter and clean the underside of the platter and the pickup sensor. It helped 99%. I noticed the speed would skip -slow down then catch up- regularly at a spot under the platter where the black paint has been stripped. Does this have anything to do with it? How do I fix this? I don't want to repair it with generic paint. Last resource, replace the platter. Any recommendations?
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Re: DENON DP 60 L RUNNING SLOW

Postby EdAInWestOC » 14 Dec 2017 20:41

That isn't black paint. The coating on the inside surface of the edges of the platter is a magnetic oxide and in it are recorded pulses. The tape head that is positioned under the platter reads the recorded pulses and it is this information that the microprocessor uses to regulate the speed.

If there is a spot where the coating is missing you will indeed have speed regulation issues. The larger the missing coating, the worse the problem. The only way to fix this is to find a replacement platter...a hard thing to do unless you find a Denon DP-60L being parted out.

Good luck finding one,
Ed
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Re: DENON DP 60 L RUNNING SLOW

Postby Spinner45 » 14 Dec 2017 21:01

EdAInWestOC wrote:That isn't black paint. The coating on the inside surface of the edges of the platter is a magnetic oxide and in it are recorded pulses. The tape head that is positioned under the platter reads the recorded pulses and it is this information that the microprocessor uses to regulate the speed.

If there is a spot where the coating is missing you will indeed have speed regulation issues. The larger the missing coating, the worse the problem. The only way to fix this is to find a replacement platter...a hard thing to do unless you find a Denon DP-60L being parted out.

Good luck finding one,
Ed


Yep.
I would *never* suggest anyone to remove the platter on those things.
Unless you're a tech, you'd never know that coating is extremely delicate, not some paint as mentioned and any careless handling of the platter will result in a crapped up machine.
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Re: DENON DP 60 L RUNNING SLOW

Postby letate » 15 Dec 2017 03:38

May I suggest taking a look at page 3 of the 60-L service manual. Pots VR1 and VR2 adjust speed for 33 and 45. If these are not adjusted properly, you can experience the condition you described. To adjust, the service manual suggests using an oscilloscope, but it can be done another way. If you are not experienced working with electrical circuits, I would suggest finding someone who is. This must be done with the turntable playing a record. So, remove the bottom, set the turntable so that you can get under it to adjust VR1 and VR2 while it is playing, minimal adjustment should be needed. Adjust until the speed is stable for both speeds - light on steady rather than flashing. Fairly easy, just need to be careful not to short anything, use a plastic rather than metal screwdriver. Radio tuning tools work well for this.
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Re: DENON DP 60 L RUNNING SLOW

Postby Spinner45 » 15 Dec 2017 09:14

letate wrote:May I suggest taking a look at page 3 of the 60-L service manual. Pots VR1 and VR2 adjust speed for 33 and 45. If these are not adjusted properly, you can experience the condition you described. To adjust, the service manual suggests using an oscilloscope, but it can be done another way. If you are not experienced working with electrical circuits, I would suggest finding someone who is. This must be done with the turntable playing a record. So, remove the bottom, set the turntable so that you can get under it to adjust VR1 and VR2 while it is playing, minimal adjustment should be needed. Adjust until the speed is stable for both speeds - light on steady rather than flashing. Fairly easy, just need to be careful not to short anything, use a plastic rather than metal screwdriver. Radio tuning tools work well for this.


As the OP menationed: "The repair shop led me to remove the platter and clean the underside of the platter and the pickup sensor.
......a spot under the platter where the "black paint" has been stripped."


Obviously, that so-called "repair shop" doesn't know a darn thing about the sensitive nature of the magnetic coating, and suggesting a customer to mess with it is pure trouble, if not stupidity.
Since this coating is damaged, it will certainly throw off the pulses induced into the tape head sensing assembly, and also corrupt the data fed into the processor which controls speed.
There are hundreds of "pulses" recorded onto that coating, ALL are needed for rotational control, and if any are missing or damaged, then the processor cannot determine with accuracy one simple rotation of the platter.
Adjustments which you described may not Help in that case, which relies on NON damaged signal flow.
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Re: Denon DP 60 L running slow

Postby letate » 16 Dec 2017 15:07

I have found the magnetic strip to be fairly resilient. The only way to tell if it is truly damaged is with an oscilloscope. Short of that, attempting to adjust vr1 and 2 is an alternative way to determine if these are out of adjustment.
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Re: Denon DP 60 L running slow

Postby fscl » 28 Dec 2017 20:29

+ 1 ltte,

Had a dirty grimy DP 35F running slow, slowly and carefully tweaked the speed pots and now my daily spinner. IIRC 45 pot first then 33 or it may just fall in line...... :-k :-k

Good luck

Fred
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