A CANADAIR CL56 IN CRUISE AT FL280; THE PUSH BUTTON LIGHT SWITCHES BEGAN FLASHING ON AND OFF DUE TO FAILURE OF THE R LIGHT DRIVER UNIT.

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AT CRUISE; APPROX 30 MINS INTO THE FLT; ALL THE PUSH/LIGHT SWITCHES BEGAN TO FLASH ON AND OFF. NO WARNINGS OR EICAS MESSAGE. HAVING SEEN THIS PROB ONCE BEFORE I KNOW THAT IT WAS A FAILURE OF ONE OF THE LAMP DRIVER UNITS. BY USING THE LAMP TEST SWITCH; I WAS ABLE TO ISOLATE THE PROB TO LAMP DRIVER UNIT (R) OR (L). WE CONTACTED MAINT CTL. THERE IS NO FIX IN THE AIR OR CHKLIST. MAINT CTL WAS UNFAMILIAR WITH THIS PROB; AND 'SAID' ONLY TO CONTINUE TO CVG (HOME BASE) IF ABLE; WITH ALL THE LIGHTS IN THE COCKPIT FLASHING ON AND OFF. I ASKED MAINT CTL IF WE COULD DISABLE LIGHT DRIVER UNIT (R) WITH A CIRCUIT BREAKER. THEY TOLD ME THEY COULD NOT DIRECT ME TO DO SO. HAVING THIS PROB ONCE BEFORE; AT NIGHT; AND WORKING WITH A MORE EXPERIENCED MAINT CTL PERSON I KNEW WE COULD ISOLATE LIGHT DRIVER UNIT (R) AND STILL HAVE LIGHT DRIVER UNIT (L)(1). BECAUSE OF THE CONTINUED DISTR; I ELECTED ALONG WITH CONFIRMATION WITH THE FO TO PULL THE CIRCUIT BREAKER ON LIGHT DRIVER UNIT (R). THIS STOPPED THE FLASHING LIGHTS. I TESTED LIGHT DRIVE UNIT (L). ALL WAS NORMAL AND LIGHT DRIVER UNIT (R) WAS INOP. THIS IS THE PROC TO DEFER A LIGHT DRIVER UNIT; PULL THE CIRCUIT BREAKER; AND TEST THE WORKING LIGHT DRIVER UNIT. WE PROCEEDED TO CVG; WITHOUT FURTHER PROBS. IN CVG WE FOUND OUT THE ACFT HAD 2 PRIOR WRITE-UPS ON LIGHT DRIVER UNIT (R). THIS INCLUDING CHANGING OUT LIGHT DRIVER UNIT (R) PREVIOUSLY. MAINT CTL COULD NOT FIND THE PROB AND IT WORKED OK ON THE GND. THE LIGHT DRIVER UNIT (R) WAS DEFERRED AND WE FLEW 2 MORE LEGS WITH LIGHT DRIVER UNIT (R) DEFERRED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THIS LIGHT DRIVER UNIT IS A MAJOR PROB ONLY BECAUSE MOST TECHNICIANS ARE UNAWARE OF ITS EXISTENCE. THE RPTR SAID THIS AIRPLANE HAD A HISTORY OF FLASHING COCKPIT SWITCH LIGHT PROBS AND 1 LIGHT DRIVER UNIT WAS REPLACED. THE RPTR STATED THE FLT MANUAL SHOULD HAVE A PROC TO ALLOW OPENING THE CIRCUIT BREAKER TO THE FAILED UNIT AND OPERATE WITH THE REMAINING OPERATIVE R OR L UNIT. THE RPTR SAID THE MEL WILL ALLOW DEFERRAL OF A SINGLE UNIT. THE RPTR SAID THIS UNIT HAS FAILED ON OTHER CL65 ACFT.