HP-67 Card Reader became very touchy

[Alevin]

(09-30-2023 01:22 AM)teenix Wrote:  The 97 has a 5V battery so the capacitor for it would be best rated for 16 or 25 volts.

You might even be able to remove the original 67 capacitor and solder a surface mount type to the circuit board pads. I think the through hole capacitor pads are spaced at 0.2 inches, so a 47uF 10V 1411 or larger 2312 type might do - nice and compact and around a dollar each.

cheers

Tony

I am afraid my soldering skills and avalaible tools are not enought to do the job without messhing something else, as a "forest" of tall components grow around the cap. For me, desoldering and soldering throuhg the PCB holes seems easier. Any way, It is a great suggestion to think about.

Some point out. The 47 uF 6 volts, dip format, has a ESR about 2 Ohms in catalogs. So, not so different for the ESR I measured on board (with a Chinese "ESR meter" ), 2,7 Ohms, for the suppoused failed Cap. Then may be is it not so faulty if the present cap is not 16 or 15 volts but 6 volts? I guess, I will not know up to change it.

Regards

Ricardo