Best method of replacing denon 2900 clock

D.A.R.R.Y.L. · 30th November 2005, 06:31 PM

Hi All,
First of all; I have searched the forum, but did not find a clear howto.

I am looking to replace the clock as a starter. I have the schematics in pdf format and have the clock ordered. I was wondering about where to connect the new clock? Guido always suggests to remove both the clock and the two adjacent caps. I saw some professional mod where, as far as I could see, only the clock was removed. What are your takes on this?

What i also do not understand is why in the original state the clock signal is fed to pin 8 of the sm8707EV clock gen? In the datasheet of this IC pin 8 is for xto and 7 for xti. Pin 7 isn't even connected!!
So what would you recommend? Only remove the original clock and hook up the new tent XO? And onto which points?
My thougts would be to only cut the trace between r169 and pin 8 from the ic105 (sm8707ev clock ic) and hook up the + of the clock there on pin 8. And hook up the - to the ground somewhere near pin 8.
It would then be very easy to restore the old clock circuitry by only reconnecting the rightside of r169 with pin 8 again. Correct me if I am wrong here. Thanks in advance!!

wa2ise · 30th November 2005, 08:26 PM

The external clock source should feed "XTI", pin 7. "XTO" is an output of an on chip device (probably just an inverter) that in turn normally drives the crystal into oscillation and in turn into the "XTI" input. All you should need remove is the crystal itself, and maybe C177. If you fed the external clock into "XTO" you'd be fighting with the internal oscillator/inverter amp's output stage. By feeding the external clock into "XTI" you're putting that stage to good use as a buffer.

Extreme_Boky · 30th November 2005, 09:35 PM

You should feed the clock signal to pin 7. Pin 8 is usually connected to pin 7 internally via 1 - 10Mohm resistor.

7pF capacitors are there to load the xtal. Clock oscillators do not need them to work.

You should remove X101, R169 and C117. Connect your oscillator to pin 7 and cut the remaining of the track as close to this pin as possible.

Consider using very good power supply for your oscillator. Noise levels have to be very low!

Extreme_Boky

D.A.R.R.Y.L. · 1st December 2005, 05:43 PM

Hi Guys,

Great answers!! Thanks.
I am using a Tenlabs XO3 clock with a seperate power supply.
Could you tell me why xto/pin8 is currently connected to the clock via R169?
And is it ok to connect the ground of the new oscillator just to the ground nearest to the SM8707 IC?

Jocko Homo · 1st December 2005, 10:11 PM

Limits current drive in the crystal.

Jocko

D.A.R.R.Y.L. · 1st December 2005, 10:15 PM

Ok.
Guido tent will send me a modified clock which outputs 3v3; so I will be save without the resistor then?

Jocko Homo · 2nd December 2005, 04:01 PM

Since the resistor is not part of the oscillator circuit any longer........yes.

Jocko

30th November 2005, 06:31 PM	#1
D.A.R.R.Y.L. diyAudio Member Join Date: Mar 2002 Location: Haarlem	Best method of replacing denon 2900 clock Hi All, First of all; I have searched the forum, but did not find a clear howto. I am looking to replace the clock as a starter. I have the schematics in pdf format and have the clock ordered. I was wondering about where to connect the new clock? Guido always suggests to remove both the clock and the two adjacent caps. I saw some professional mod where, as far as I could see, only the clock was removed. What are your takes on this? What i also do not understand is why in the original state the clock signal is fed to pin 8 of the sm8707EV clock gen? In the datasheet of this IC pin 8 is for xto and 7 for xti. Pin 7 isn't even connected!! So what would you recommend? Only remove the original clock and hook up the new tent XO? And onto which points? My thougts would be to only cut the trace between r169 and pin 8 from the ic105 (sm8707ev clock ic) and hook up the + of the clock there on pin 8. And hook up the - to the ground somewhere near pin 8. It would then be very easy to restore the old clock circuitry by only reconnecting the rightside of r169 with pin 8 again. Correct me if I am wrong here. Thanks in advance!! __________________ {Marantz CD-7 Guido Tent Clock ---> HMS Sestetto MKII XLR ---> Electrocompaniet ECI-4 ---> Kimber 8TC ---> Eros MKII DIY}

1st December 2005, 05:43 PM	#4
D.A.R.R.Y.L. diyAudio Member Join Date: Mar 2002 Location: Haarlem	Hi Guys, Great answers!! Thanks. I am using a Tenlabs XO3 clock with a seperate power supply. Could you tell me why xto/pin8 is currently connected to the clock via R169? And is it ok to connect the ground of the new oscillator just to the ground nearest to the SM8707 IC? __________________ {Marantz CD-7 Guido Tent Clock ---> HMS Sestetto MKII XLR ---> Electrocompaniet ECI-4 ---> Kimber 8TC ---> Eros MKII DIY}

1st December 2005, 10:15 PM	#6
D.A.R.R.Y.L. diyAudio Member Join Date: Mar 2002 Location: Haarlem	Ok. Guido tent will send me a modified clock which outputs 3v3; so I will be save without the resistor then? __________________ {Marantz CD-7 Guido Tent Clock ---> HMS Sestetto MKII XLR ---> Electrocompaniet ECI-4 ---> Kimber 8TC ---> Eros MKII DIY}

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30th November 2005, 08:26 PM	#2
wa2ise diyAudio Member Join Date: Apr 2005 Location: NJ	The external clock source should feed "XTI", pin 7. "XTO" is an output of an on chip device (probably just an inverter) that in turn normally drives the crystal into oscillation and in turn into the "XTI" input. All you should need remove is the crystal itself, and maybe C177. If you fed the external clock into "XTO" you'd be fighting with the internal oscillator/inverter amp's output stage. By feeding the external clock into "XTI" you're putting that stage to good use as a buffer.

30th November 2005, 09:35 PM	#3
Extreme_Boky diyAudio Member Join Date: Dec 2003 Location: Sydney	You should feed the clock signal to pin 7. Pin 8 is usually connected to pin 7 internally via 1 - 10Mohm resistor. 7pF capacitors are there to load the xtal. Clock oscillators do not need them to work. You should remove X101, R169 and C117. Connect your oscillator to pin 7 and cut the remaining of the track as close to this pin as possible. Consider using very good power supply for your oscillator. Noise levels have to be very low! Extreme_Boky

1st December 2005, 10:11 PM	#5
Jocko Homo Banned Join Date: Feb 2002 Location: As far from the NOSsers as possible	Limits current drive in the crystal. Jocko

2nd December 2005, 04:01 PM	#7
Jocko Homo Banned Join Date: Feb 2002 Location: As far from the NOSsers as possible	Since the resistor is not part of the oscillator circuit any longer........yes. Jocko

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