[time-nuts] FE5680 missing PPS soln

[Attila Kinali]

On Fri, 3 Feb 2012 09:50:52 -0000
"Rob Kimberley" <robkimberley at btinternet.com> wrote:

> Mine was a green LED out of the junk box, but I did use 330R in series. 1k8
> seems rather large.

Then i'm not surprised that your FE-5680 refused to work :-)

Just calculate: 5V supply, approx 2V LED voltage -> 3V over the resistor.
3V/330R = 90mA. As i wrote already, the 74AC240 has it's absolute
maximum rating at 50mA. For a general logic output, i wouldn't recomend
to draw more than 10mA (as Bob Grant wrote, the lock signal doesn't
seem to pass trough the 74AC240). Hence, i would say that 330R seems
rather small :-)

Keep in mind that you drove circuit at over current for quite a long
time. The circuit is most likely damaged (if they dont have an over
current limit, which i doubt). If for an unknown reason the lock signal
fails in the future, it might be due to this.

			Attila Kinali
-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin