Had another go at rescuing my first semi successful attempt, this time resoldering from inside the firebox, I took more care with insulation this time, all cosily wrapped in kaowool backed up with insulating blocks, the firebox also filled with insuation block offcuts.
Tried to keep flame from direct impingement on solder but found this to be not easy with a powerful flame in a relatively small area, flux seemed to be fizzing away far too soon. After what seemed to be an eternity I began to think it was not going to work again then suddenly the solder just flowed.
Thus encouraged, the next day I proceeded to solder in the firebox and ring. All seemed to go well but on inspection afterwards, another disaster, two of the tubes became unsoldered and dropped out.
Problem is they did not just fall out loose, the molten solder ran down the tubes and resoldered them to others, got to work out how to free them and resolder in.
Should I have insulated them from the heat more when I was soldering in the firebox and ring?
Reading through this sorry tale makes it all sound a bit amateurish, I guess I am learning the hard way.
Bill D.