Mechanical tach failure?

wrote in message
...

How about either a change inmagnetic flux or a change in the position
of the EC (Edy Current) ring?

A weakened magnet would cause the reading to DROP. So something that
causes the aluminum disc to get closer to the magnet would cause the
RPM to read high, or something that causes the air movement from the
spinning magnet to influence the disc - like a bit of oil or grease
from the cable migrating into the instrument.

Like I said, everything looked fine inside (no dirt or grease). There is a
scuff mark on the inside of the disk which could be new or old. If lubing
the cable doesn't do the trick, I'll probably send it out to be rebuilt;
unless the cost is more than another used unit.

Thanks,
Rich S.

"Rich S." wrote in message ...
wrote in message
...

How about either a change inmagnetic flux or a change in the position
of the EC (Edy Current) ring?

A weakened magnet would cause the reading to DROP. So something that
causes the aluminum disc to get closer to the magnet would cause the
RPM to read high, or something that causes the air movement from the
spinning magnet to influence the disc - like a bit of oil or grease
from the cable migrating into the instrument.

Like I said, everything looked fine inside (no dirt or grease). There is a
scuff mark on the inside of the disk which could be new or old. If lubing
the cable doesn't do the trick, I'll probably send it out to be rebuilt;
unless the cost is more than another used unit.

Thanks,
Rich S.

Look closer. The inboard end of the shaft that carries the needle
fits into a tiny bore in the inboard end of the input shaft to keep
the magnet and drum concentric with one another. This close fit is
subject to dried-out lube or a bit of grit interfering with the needle
shaft's freedom and drives the needle up. Or it might be worn to the
point that it's chattering and adding friction, with the same result.

Dan

"Dan Thomas" wrote in message
om...

Look closer. The inboard end of the shaft that carries the needle
fits into a tiny bore in the inboard end of the input shaft to keep
the magnet and drum concentric with one another. This close fit is
subject to dried-out lube or a bit of grit interfering with the needle
shaft's freedom and drives the needle up. Or it might be worn to the
point that it's chattering and adding friction, with the same result.

Thanks, Dan. If you read my other post to Cy, you'll know that since I
didn't find anything my limited talents could repair I'm choosing the
cheaper option of replacing it with a used unit rather than a rebuild.

Now if I could just get the rest of me repaired or rebuilt!

Rich "My needle is worn to the point of chattering" S.