Speedometer and Tach Malfunctioning

[wildrose196812]

I've just recently joined this forum and have purchased an 82 300SD. The Speedometer and the Tach/clock don't work. The odometer does function properly. When I pulled out the instrument panel, I noticed the solder around the electrical connection pin that connects to the speedometer wire (green/black) was cracked. I resoldered the connection and the speedometer still does not work. Doing a search on the forum didn't give me many threads on my situation, because my speedometer seems to be an electrical signal and not a mechanical cable.Can anyone point me in the right direction or do have to purchasse another speedometer and if so where can I purchase one. Also can anyone help me in regards to the signal I should be receiving from the tach sending unit coming into the tachometer so I can ensure the sender is working properly or not. Help and Thanks...