Tachs are very simply.  Its a volt meter, and a R/C filter at a given
frequency.  Kind of like the power supply filter.  The high the
frequency the more voltage gets thru. Obviously that filter is bad
                                                         Eric.

David Beierl wrote:

> Hello Volks -- couple days ago my tach turned up its toes -- any time
> power
> is applied it runs up to just below the mechanical stop (well
> offscale) and
> hangs there.  Anyone with schematics and/or practical troubleshooting
> experience with these?  I haven't pulled the cluster yet, though I did
> get
> a reminder that the primary coil pulse is available at a terminal on the
> back of the tach...ouch <g>
>
> Thanks,
> david
>
> --
> David Beierl - Providence RI USA --
> http://pws.prserv.net/synergy/Vanagon/
> '84 Westy "Dutiful Passage"
> '85 GL "Poor Relation"
>
>