LYNN – An electrical clock bolted to the exterior of the former Equitable Cooperative Bank at the corner of Oxford and Willow streets burst into flames Wednesday afternoon, causing downtown traffic snarls as firefighters raced to the scene.No cause was given for why the device went haywire.Firefighters from Engine 1 and Ladder 2 responded. The sign was fully engulfed in flames when they arrived, attracting a crowd of onlookers. A hose line was hoisted to the extended ladder, allowing firefighters to douse the hot clock.The bank building was restored in recent years by the Don Baker real estate agency, which temporarily occupied the address as its headquarters before moving to Chestnut Street.