[chbot] 6809 Processors

[Charles Manning]

Welders and compressors are a **huge** inductive load that cause all sorts
of phase shift etc. They can also cause huge ground currents etc. The noise
can be induced in many ways.

Fitting ferrites has to be done right, with a full understanding of what
noise you are trying to nobble otherwise you can actually make things
**worse**.

For example, if you are trying to kill a common mode signal (which these
often are), then all the conductors for the cable should run through the
same ferrite. Putting them through individual ferrites does not help, and
can make it worse.

If it is differential noise, then a common-mode ferrite does nothing
useful, but can make it worse.

Although parts can get more static sensitive with age, I doubt that is what
is happening here. More likely the increase is due to either observation
bias or other environment changes.


I'm guessing that to make everything worse this is a 2 layer board.

Try an isolating power supply. See if that helps.

Good luck. you will probably need it.



On Mon, Feb 3, 2014 at 8:40 AM, Marshland Engineering <
marshland at marshland.co.nz> wrote:

>  This is one for the oldies (I may be wrong) who played with micros 30
> years ago.
>
> I have a CNC mill which forms most of my income. It's old but very useful
> and accurate. It uses a 2 x 6809 processors to do the work.
>
> Several years ago, the control occasionally freezed when the large
> compressor started. I say freezes but sometimes it just displays rubbish. A
> switch off and on restores the controls.
>
>
>
> I swapped the large single phase compressor for a 3 phase one and the
> problem went away.
>
>
>
> Then about 18 month ago, I found that whenever I welded with a high
> frequency start, again the display would, at times, freezes. It's gradually
> getting worse and I'm getting worried. I loose my set-up each time it
> freezes. I added ferrite beads to some of the interconnecting cables and
> changed the PSU caps (someone else recommendation) but hasn't really made
> much difference.
>
>
>
> Is it an earthing issue, or do filter caps near the processors get old, or
> a any other component past its sell by date ?
>
>
>
> If you think you can help, I'd be happy to trade machining time for fault
> finding time or similar.
>
>
>
> Thanks Wallace
>
>
>
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