Originally posted by pres589 I had the plus facing out to start. Tried reversing it just to be sure and it didn't do anything, turned it back. Just re-verified; positive side is facing out towards the cover. Needle still goes to the top of the range.
It has been years since I had mine apart for meter adjustment and I can't remember the details of the meter circuit except that it is very simple and that the shutter speed dial drives movement of a long strip resistor that curves around the top of the lens mount under the front cover. There a set of feeler contacts make the circuit with the meter cells and display needle. It may be that a solder joint has broken somewhere or a capacitor gone dry. Removal of the top and front covers expose the components and wiring.
As for using a hand-held meter*, it works the same as the built in meter**. You take a reading, set the camera/lens and shoot at will with those settings until either the subject or light changes.
Steve
* Most hand-held meters don't feature spot metering. Most average reflected light within about a 30° angle. The better units also allow for incident metering where one measures the light falling on the subject from the direction of the camera. An incident meter is equivalent to using a gray card.
** The built-in meter on the Singlex TLS averages the full screen the same as a Pentax Spotmatic.