Most folks have no end of trouble with mechanical retracts and seldom if ever get them functioning properly the first time around. Its for this reason that is the reason the fellow you got the ship from said the retracts were not working. Its likely they were never setup properly since the ship was new. Its also likely the reason you let the smoke out of the servo by not assureing the proper mechanical linkage before trying to cycle.

The same could happen even to the new servo you ordered if you don,t start over with the linkage. You see as oppose indicated in his post a retract servo is not proportional once triggered it will continue to run its full travel no matter what and when it reachs its full run it will shut off with no drain on the battery if something impedes its journey to full travel, something such as a maladjusted linkage it will keep trying to force it to keep moving and this will tend to dump your flight pack battery or it could cause a motor burnout which seems to have happened to you. A retract servo will not respond to end point adjustment in programing.

The thows of the actuation rods must be adjusted strickly with linkage and this is done normally with either star shaped or round servo output wheels. Betcha never knew what thos round ones were for Huh. The idea is to drill your own holes in the round output arm for the S bends on the actuation rods to acheve just the right total throw or trave of the rod.

John