Now you're giving us key information not present in your original post. If the hissing sound only occurs when power is applied, then it's not a cracked crt. When you originally wrote that you reattached the board and then hissing occurred, you gave us no details about intervening events (leading us to believe that there were none).
Several electronic sources of hissing exist, so without a soundfile to listen to, it's hard to provide a definite diagnosis. But a common source is a high-voltage problem (e.g. a loose HV connector, damaged insulation...). Did you operate it long enough to see if the crt displayed something/anything?
