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Old 22nd January 2004, 06:44 PM   #1
Lyra is offline Lyra  Norway
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Default What is this resistor ???

When removing a clock there was a resistor mounted across the clock output (see picture).
After listening to my CDP I have decided to move the LCAudio-stuff back where it came from, but this resistor dissapeared when it was removed. I measured it thow, and the value was 500 ohm.

anybody know what the purpose of this could be ??
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Old 22nd January 2004, 09:48 PM   #2
JohnW is offline JohnW  Hong Kong
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If the original component was a resistor, then it was used to crudely terminate the clock. I would be surprised if it was 500R as this sounds a bit on the high side. 50R maybe…

From your photo, I cannot read the “resistors” colour bands.
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Old 22nd January 2004, 10:32 PM   #3
Lyra is offline Lyra  Norway
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I am sure...it was 0,5K ohm readout on my multimeter. I checked it out several times just of couriosity.
Didn't understand what it was....

Don't remember the color-code right now, but from another picture I got it seems like GREEN, GREY, GREY, BLACK, and with BROWN "alone" on the other side. But the quality of the pictures could have been better...
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Old 23rd January 2004, 09:49 AM   #4
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Quote:
Originally posted by Lyra
I am sure...it was 0,5K ohm readout on my multimeter. I checked it out several times just of couriosity.
Didn't understand what it was....

Don't remember the color-code right now, but from another picture I got it seems like GREEN, GREY, GREY, BLACK, and with BROWN "alone" on the other side. But the quality of the pictures could have been better...

it was very likely in series with the output of the original oscilator, driving the crystal

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Old 23rd January 2004, 09:52 AM   #5
JohnW is offline JohnW  Hong Kong
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Wish I could help more, if it where a resistor from the colours you gave it would be 588R? maybe – but to the best of my knowledge you cant get a 588R resister – not in any E series that I’m aware of?

However, I guess the unit should work OK without it?

In any case, I would not worry about correctly terminating the clock – looking at the crude wiring from the clock board, its not as if it’s a controlled impedance… and who knows what the output impedance of the clock board is anyway?

I also don’t believe that adding an external clock to the DSP decoder in your DVD player is going to improve matters – if anything it can only make matters worst with extra noise due to external ground loops, mis-termination, and noise that is no longer Common Mode, Pls. let me explain: -

By removing the crystal from the board, still leaves the internal oscillator circuit in the DVD decoder, the fact that you have an external input, will not reduce the phase noise of the internal oscillator, PLL and clock distribution paths.

The DVD decoder IC spends the majority of its time decoding the MPEG video at Line and Frame rates – 50/60Hz & ~16KHz. If you where to run a phase noise plot of the Audio Master clock generated by the decoder, you will find massive amounts of 50/60Hz & ~16KHz spurie – these products are directly in the audio band!

With the very poor inherent phase noise of the DVD decoder, I would be extremely surprised if you would see any reduction by adding an external clock oscillator. Any sonic “Improvement” will be due to a change, but not reduction in Phase Noise (jitter).

Has anyone seen any “before & after” jitter results from upgraded DVD players that has an INTEGRATED PLL + Decoder? There might be a small improvement to units fitted with and external PLL clock generator such as from Burr Brown / NPC.

At least with the clock upgrade – the previous owner of the DVD player wasted their money!
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Old 23rd January 2004, 09:55 AM   #6
JohnW is offline JohnW  Hong Kong
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If you take a closer look at the photo, you will see that the “Component” is fitted in Parallel, and not series with the clock lines.
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Old 23rd January 2004, 10:02 AM   #7
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The resistor provides a termination for the wires and reduces reflections.
With the resistor removed, there is no termination to damp the reflections.
Install a 560 ohm resistor and the circuit will be happy.
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Old 23rd January 2004, 10:14 AM   #8
UrSv is offline UrSv  Sweden
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Well, I would make sure it is a resistor. It looks a lot more like an inductor to me. If that makes sense in that position I can't say.
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Old 23rd January 2004, 10:18 AM   #9
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If the mystery part measured 500 ohms, it is certain to be a resistor.
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