How to add reclock in Philips CD303
How to add reclock in Philips CD303?
Could anybody can teach me?
Thanks you very much!!
Do you mean an aftermarket clock ?
I have Philips CD350 and interested in that too...
For instance, if to buy some aftermarket clock from ebay like this?
should a quartz simply be replaced by new clock + feed the clock with 6v?
Hi, First you should open up the machine and see what frequecy the crystal
is using for the laser decoder (SAA7XXX).For Philips it is commonly 16.934Mhz. but it can be another frequency depending on which model it is.
After you know the frequency then get the correct clock module,
of course the power suppy differ from one to another but generally it
is DC volts but the one you showed is 6V AC? If so depending on what
power voltage on your machine you can tap accordingly or modify/add another
transformer or DC rectification.
Follow the instructions provided with the clock module ( electrical connections) and you will have no problem. Hope this helps.
PS you may need to remove the caps connected to old crystal if instructed by the particular clock module.
You can download Philips cd303 service manual but it is in dutch language! The schematics is all you need.
many thanks! It appears to be quite simple :)
finally found the clock that seems to be quite decent for my Philips CD350 :)
btw, could anyone pls advice which transformator is better to choose as clock's PS? should it be toroidal obligatory and what should be the min VA (10 or 20 or even higher?)
10VA is probably too much for the clock.
I do not think there is any difference between transformers, apart from mounting them.
That's a nice ocillator with 1ppm temperature compensated but
let's say we take it as face value the claim of 1ppm accuracy,you need a very
low noise power supply and the one on the pcb is well a standard one perhaps
better than a plain 3 pin regulator.Anyway you get what you pay for.
It's easy to calculate the VA (volt ampere or power in watts) needed for a transformer by using Ohm's law.You can check for a typical TXCO how much current it uses from the datasheet and the 74hc163 it would actually not be much.
So for illustration we use a figure of 100mA which is way in excess of the
true value.The input voltage needed by clock pcb as shown is from 7-20 volts
DC.For lowest noise pick a lower voltage,eg. 9V is commonly available.
(Assuming TXCO and 74hc163 are 5V rated.3V headroom for 3pin regulator.)
VA=current X voltage =100mA X 9V= 0.9VA ~ 1VA
Add some 10% or more for transformer losses and the common VA values
you will see in catalogues is from 2 ,3,4,5,6 etc. So closest will be 2VA.Even
a 3VA is no harm.Do not use one that is too big as the space available in the
cd player is limited.
PS as you can see it has a "frequency divider in 74hc163" ,if you are only using
16.934Mhz you tap from the stated take off solder pads and it is preferable to
cut the power trace to 74hc163 and reconnect from the output of TXCO removing one noise source in the 74hc163.(ie. not use the 74hc163).
If you don't feel confident about diy then use as is.
I really appreciate your explanation and help! :cheers:
read somewhere in the web that toroidal transformers are slightly better to use for audio purposes, so probably will be looking for such as there is quite a lot of space in my CD350.
Frankly speaking I'm not a DIY expert, even more - this would be my first CD tuning, so I guess I will leave the clock module as it's now. Maybe later replace the caps with Elna or OSCONs...
Btw, just to confirm that clock module should be shielded, shouldn't it? and will a 1mm copper plate be enough for that?
Take care not to over tighten the bolt of the toriod but if you are
using a molded or encapsulated toriod then this is not an issue as there are
tabs for the holes.I don't think it is critical to shield the clock pcb as you may accidentally make contact with some part and shorting the circuit.If this is an instrumentation equipment ,it may be wise to shield as you want to make accurate or precise measurements.A copper plate alone will not give
proper or adequate shielding as the radiation can go over or around .
Fully enclosed is better but a hassle ( the clock pcb ) but that does not mean you can't use it if there is space to install, better than no barrier?. Singa
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