nsc module's running slow

[jagmad]

Hi all
I have just picked up some NSC modules and several of them have the same problem.
Running slow or very slow the thing is it's not like it's 1/2 speed or 1/4 speed it's different
with them all.
I thought they just wasn't running at all because you have to keep the button pressed in for at least
3,4 or 5 seconds to bring up the running seconds display.
Or should I say not running seconds display as it's so slow.

Hey maybe I should put them in a dark room with the Hughes one I posted about a while back,
that's running double and quadruple time.
See if they mate and have little modules that run 60 seconds a minute?

No seriously is it most likely to be the crystal?
Or is there some other reason.
Thanks in advance Jag.


Ps. check my post about the Hughes I have an update.

[Old Tom]

It is and it isn't the crystal- what is probably happening is that the oscillator circuit is running in short bursts, If you have a very high input impedance oscilloscope you could see this happening- the oscillation starts at a very low level, rapidly builds up and saturates the input amplifier causing it to shut down till the excessive charge dissipates. Just why this happens can be down to a whole load of causes- damage to input transistor, feedback resistor gone high etc etc. Cleaning the circuit board thoroughly and changing the crystal for a more modern one may cure this (and don't forget to clean the board again after soldering in your new crystal).

[jagmad]

Thanks for the tip's/info Tom it's much appreciated.
I have given them a bath but I have to admit I seem to get
better results if I finish off with electrical solvent spray on a swab.
Which I didn't do this time. Don't know why.

As for the modern crystal can anyone from the UK point me in the right direction.
of some good ones, Or should I just stick to Maplins?
As I have no means of testing them before fitting.
Other than fitting one to a working module I suppose.
I've only ever fitted ones harvested from working ones with segments missing
due to wire bonds being broken.

Again
Jag