[sdiy] crystal oscillator oscillator seeming to run at wrong frequency
dragons
dragon.servicing at googlemail.com
Sun Nov 15 20:23:01 CET 2009
Hi,
sorry if this question is off topic.
I've been looking at a video generator board that has two crystal
oscillators on it, one is at 14.318 Mhz and 17.734 Mhz.
( these are for the ntsc and pal standards ).
both use a 74lcx04 ic with 1Mohm feedback resistor and 22pf caps.
but the frequency of the 14.318 crystal measures 14.322 , the other is
much closer to the 14.318.
the chip the clocks drive is the Epson S1D13806
supply voltage is 3.3 volts.
I just wondered if it is possible that this might be a design fault with
the circuit ? I've got a replacement crystal on order.
the video card would normally be used set to the Pal output but when I
use it with a multistandard monitor and set it to ntsc the ntsc light on
the monitor doesn't illuminate.
regards Peter B
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