AN SMA PLT'S DIRECTIONAL GYROSCOPE MISBEHAVED AT NIGHT IN THE WX.

Narrative

I WAS IN CONTACT WITH BOSTON APCH. I HAD ADVISED I COULD MAINTAIN 140 KTS ON FINAL. BOSTON CHOSE TO KEEP ME CLOSE TO LOGAN AND WORK ME INTO FINAL WHEN SEPARATION OF ACFT ALLOWED. AT 2000 FT MSL; WHILE INTERCEPTING ILS 4; MY ORIGINAL EQUIP 1964 DIRECTIONAL GYROSCOPE TEMPORARILY PAUSED WHILE TRACKING MY L TURN ONTO THE LOC. IT PAUSED FOR 2 SECONDS; THEN ROTATED RAPIDLY AS IF IT HAD HUNG UP AND RELEASED. MY DIRECTIONAL GYROSCOPE HDG WAS NOW INCORRECT. I CHOSE TO NOTIFY LOGAN APCH OF A MISSED APCH. WHEN SETTING THIS STYLE DIRECTIONAL GYROSCOPE; YOU MUST PUSH THE SET KNOB IN AND SCROLL THE HORIZ INDICATOR TO MATCH THE MAGNETIC HDG. I THOUGHT THAT I MAY HAVE INADVERTENTLY NOT PULLED THE KNOB BACK TO ACTIVATE THE DIRECTIONAL GYROSCOPE. WHEN LOGAN APCH STARTED NEW RADAR VECTORS FOR RWY 4R IN LOGAN; I NOTICED A CONSIDERABLE LAG IN THE DIRECTIONAL GYROSCOPE MAINTAINING ACCURATE HDG CHANGES. AT THIS TIME; I NOTIFIED LOGAN APCH THAT MY DIRECTIONAL GYROSCOPE WAS MALFUNCTIONING. I RECEIVED RADAR VECTORS TO BEVERLY; MA (30 MI N). WHEN CLR OF CLOUDS; LANDED VFR. NO MAJOR INCIDENT. THIS WAS MY FIRST MISSED APCH IFR/IMC; ACTUAL/NON-TRAINING. LOGAN ATC HAD ME CALL THEM BACK ONCE ON THE GND; BEVERLY. I SPOKE WITH THE NIGHT ATC SUPVR. HE QUESTIONED ME. I APOLOGIZED FOR ANY INCONVENIENCES CAUSED LOGAN ATC. HE STATED NO PROB; THAT'S WHY THEY ARE THERE. REMEDY: I HAVE ORDERED A NEW AUTOPLT SYS WITH NEW UPDATED VERT/360 DEG FACE DIRECTIONAL GYROSCOPE INSTEAD OF THE OLD 1964 HORIZ SCROLL DIRECTIONAL GYROSCOPE WITH 30 DEG HDG WINDOW.