AN ACR DC9 FLC WITH A KNOWN MALFUNCTION TKOF ANYWAY AND ENCOUNTER ANOTHER; MORE SERIOUS PROB. THEY RETURN TO THEIR DEP ARPT WITH SMOKE IN THE COCKPIT.

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WE DEPARTED ATL FOR CAK WITH 108 PAX AND 5 CREW ON A SCHEDULED PART 121 TRIP FOR AN ACR. OUR ACFT WAS A DC9- 32. ON OUR CLBOUT OF 12000 FT; WE NOTICED AN UNUSUAL ODOR AND CALLED OUR #1 FLT ATTENDANT UP TO ASK IF SHE SMELLED ANYTHING IN THE CABIN. SHE RPTED NO CABIN ODOR; BUT SHE COULD SMELL AN ODOR IN THE COCKPIT. WE DECIDED TO LEVEL AT 15000 FT AND REQUEST A RETURN TO ATL. WHILE TURNING BACK WE THEN NOTICED SMOKE AND DECLARED AN EMER AND REQUESTED THE CFR EQUIP TO BE OUT FOR OUR LNDG. WE DONNED OUR OXYGEN MASKS AND SMOKE GOGGLES AND ACCOMPLISHED THE SMOKE REMOVAL EMER CHKLIST UP TO OPENING UP A COCKPIT WINDOW WHICH WE FELT WASN'T NECESSARY AT THAT POINT BECAUSE WE STILL HAD A VERY SMALL AMOUNT OF SMOKE AND COULD SEE CLRLY INSIDE THE COCKPIT. WE THEN COMPLETED OUR DSCNT AND APCH AND BEFORE LNDG CHKLISTS AND LANDED UNEVENTFULLY ON RWY 26R AT ATL. THE CFR PEOPLE COULD SEE NO SMOKE OR FIRE AND OUR FLT ATTENDANTS FOUND NO SMOKE IN THE CABIN SO WE TAXIED IN TO A GATE AND DEPLANED AT A JETWAY. COMPANY MECHS FOUND AN AUTO SPOILER ACTUATOR BOX TO BE OVERHEATING AND BURNING UP THE WIRING ATTACHED. WE FELT WE; AS A COCKPIT CREW; PERFORMED WELL; BUT WERE HAMPERED BY OUR INABILITY TO COMMUNICATE WITH OUR OXYGEN MASKS ON WITHOUT CONTINUALLY SWITCHING THE MIKE SELECTOR FROM COM TO INTERCOM TO TALK TO ATC AND TO EACH OTHER. THE ACTUATOR BOX HAD BEEN INSTALLED JUST PRIOR TO OUR FLT. I AM NOT PRIVY AS TO WHY THIS BOX MALFUNCTIONED. JUST PRIOR TO OUR TKOF THE 'STALL INDICATION FAILURE' ANNUNCIATOR LIGHT CAME ON. WE PERFORMED THE ABNORMAL PROC FOR IT; BUT IT STAYED ON. WE FELT THE WIND (20-30 KTS) HAD CAUSED THIS SO WE ELECTED TO DEPART HOPING IT WOULD GO OUT ONCE WE STARTED OUR TKOF ROLL. THE LIGHT REMAINED ON THROUGHOUT THE FLT.