Successful musical entitles usually have pretty good reason for disbanding.

According to lead guitarist Tom Principato, poor management, bad record deals and differing musical directions led to the demise of Powerhouse in 1977. Last night at the Childe Harold, all eight members of the original band gathered again to reaffirm the strong R & B identity they shared for six years.

Despite the lengthy hiatus, the group's sound coalesced immediately when they opened with a couple of exuberant jump tunes, sparked by the riff patterns of Dave Birkin on tenor sax and John Wolf on trombone.

From there on out, vocalists George Leh was at the controls. Leh, who looks a little like pop singer Paul Williams and sings a lot like blues shouter Cleanhead Vinson, is equally versed in Memphis, Chicago, Kansas City and West Coast R & B styles. Each selection he performed spotlighted a particular member of the ensemble.

Principato with his pinched phrasing excelled on B. B. King's "Shush Your Mouth"; Dave Maxwell's piano added just the proper blues shading to Ray Charles' "Hard Times," and Pierre Beauregard supplied the ice-cold chords on mouth harp for Willie Dixon's "My Babe."

All musical reunions should be so successful.