Power levels of AAA size cells used to power the laser finder are short lived. A small drop in voltage and the laser output is reduced considerably, using AA Lithium increases battery life manyfold.
.As my illuminated optical finder requires 2.5 volts with only milliamp drain, I decided to power both laser and optical finder from the one external power source and redesigned the control panel to accommodate them. Two power outlets were needed, one at 2.5 volts for the optical finder and a second at 3 volts for the laser. See the illuminated optical finder as described previous IIS.
The metal case of the laser provides the positive voltage to the internal circuit - that is, the positive terminal of the battery rests on the bottom end of the case and the negative end of the second battery provides the negative voltage to the circuit via the small spring terminal within the top section of the laser. You can check this out for yourself by loading the two batteries as directed and with a multimeter set to DC volts hold the negative probe on the negitive end of the battery and the positive probe on the outside of the case. If they are new batteries you should get an unloaded voltage some what better than 3 volts.
To make a substitute for the two batteries and provide an external longer life supply,the bottom end of the laser case is drilled through with a 1/8 inch drill to provide an exit point for the small twin power lead. See pic 1.
The plastic case of a used drawing pen that just slides into the laser case, was cut to the length of two batteries and two brass plugs turned to press into the tube. The bottom plug is drilled with a 1/8 inch hole and the top plug drilled with a 1/16 inch hole. NOTE! The top plug must be less than the over-all dia of the plastic tube. It must not touch the laser case or it will short out the batteries. Sufficient negative lead is stripped of its insulation and the braded wire tinned and passed through the 1/16 inch hole in the top plug and soldered. The twin lead is threaded through the bottom plug and the positive lead bared, tinned and soldered on the inside top of the plug. Both plugs are then super glued into the tube.
See Pic 1. I used a 1/8 inch dia twin cable which appears as one in the picture and the top plug is difficult to see because its dia is the same as the inside bore of the plastic tube. The assembly is inserted into the laser tube in lieu of the two batteries and the lead/s are threaded through the bottom hole. Be sure to observe the polarity when adding the plug etc.
Pic 2 shows the Laser in the bracket on the scope and the power lead is carried around and down with the illuminated finder lead to the control panel, which clamps onto the elevation bearing. I used coloured RCA plugs for positive connection and to identify each circuit. The female plugs being the stereo connection to an early tape recorder. The switch and pot on the control panel belong to the optic finder illumination. A divice that is well worth making!
For those who may be unaware of the characteristics of small dry cells, they have a shelf life! If they are removed from the apparatus and placed in a plastic bag or container on the bottom shelf of the refrigerator their life span can be increased many fold. Something stores should do. The best place to purchase dry cells is the store that turns their stock over quickly.
