Keastman:

Thanks for the note and info. The problem symptoms are the "service" amber light on and the alarm beeps about every 30 seconds, with an error code of either 121 or 120 on the lcd display. This cell has me a bit baffled because according to the tech info (which I obtained by posing as a pool service type) there should be 32-38 volts dc on the cable when disconnected from the cell. Instead I measure about 11 volts dc when disconnected and 38 volts when connected. I already changed the back board (printed circuit board) and same symptoms. Guess it must be the cell but sure hate to gamble on it for $510. If you or anyone else reading this has any ideas, I welcome them. Thanks very much.

Ken