Just getting back to the runaway beast. It is stable but will blow rail fuses without any input or output connected. Lee has sujested a latch up somewhere. The 500 has the following differences on the backplate.
.39 ohm emitter resistors
only .05 uf caps on the rails to ground (700 has .33)
there are no fly back diodes
I have changed the power caps as the capacities were different on the ones it came with (15,000 and 18,00- which measured about 21,000 , to balanced 15,000 ones and will try first that change up.
Any my comments on fly back diodes anyone?