[turretslug]

There's the biassing circuit loss to take into account- I forget the value necessary for the R1155 but if it was, say, -30V, then that needs to be added to the optimum +220V HT to get the best-case 250V loaded overall output from a PSU- as Don (vosperd) points out, the HT- situation/connection in the PSU in question needs to be checked.

Colin