SP50 standard with 2 front buttons inop

Al · Post by Al » Wed Feb 01, 2006 8:32 am

Does anyone know what the voltages at the uP pins should be when either of the two front buttons are pressed? This one's kinda got me stumped....other than a bad uP, can't find anything obviously wrong with the KP, associated chip resistors or PCB traces. The voltages *do* change when either front button is pressed, but no beeps from the radios speaker and no button functionality. Obviously the programming has been checked. Radio works fine otherwise.

Lake Effect · Post by **Lake Effect** » Wed Feb 01, 2006 9:25 am

Do you have about 5 volts at pin 22 of the uP? I have found many with same problem and resistor R403 (100K) cracked or missing.

Al · Post by Al » Wed Feb 01, 2006 9:48 am

4.92V at pin 22, and a millivolt or two at pin 21(gnd ref.). Still looking for ideas......

Lake Effect · Post by **Lake Effect** » Thu Feb 02, 2006 9:12 am

I checked an SP50 here and found uP pin 15 at 2.3 volts and pin 19 at 3.4 volts when monitor button pressed. Both were 5 volts normally.