Re: Electronics gurus please help

--- In CAD_CAM_EDM_DRO@y..., Vajk Fekete <vajk.fekete@o...> wrote:

> so experts: at a chopping frequency a couple 10Khz, could the pcb

layout have this much influence? i checked all the components, all
the connections, spent about 2 days on it, so i am 98% that the

> working and not working circuit only differs in the shape of the

traces.

>
> i am no EE, but have some electronics building experience, more

from the digital world. and i do not have a scope, so cannot check if
the timer is working ok or not.

>
> any ideas are welcome,
>

While it is not impossible that 10 KZ can "crosstalk" the possiblity
is so low as to be ranked with earth wabble as a possible cause. If
you were going to have layout problems it would have been with your
hard wired version. 10KZ (and most of its harmonics) are in the
audio range with a wavelength of several meters. You start to get
into trouble with circuit layouts when the lengths of parallel
conductors are the 1/4 or 1/2 or 1 of the wavelength of the main
frequency or one of the low order harmonics. Even if there were
interference it would be intermittent and appear as instability or
lost steps.

Most likely you have one of the following:

1. Cold solder joint(s) (easy on bare copper boards)
2. Hairline crack in one of the conductors (use a strong magnifing
glass to locate)
3. Component in backwards or the wrong value
4. Tiny copper "short" caused by scratch on master

Check these things carefully and you will probably find your problem