Fred McKenzie wrote in message
...
In article , "N_Cook"
wrote:

800 watt toroidal transformer operating at say 400 watts. Secondaries
lead
to conventional bridge rectifier and smoothing caps for +/- rails. A
break
appears in the DC rails central 0V return to the transformer, could that
lead to a blown mains fuse, via inductive action?

N_Cook-

It depends on the circuit. If the center tap opens, then voltage
between each side and ground will be determined by the ratio of each
side's resistance to ground. If one side's voltage gets so high that it
causes components to break down, resulting high current might blow the
mains fuse.

An open center tap might upset circuit balance so that everything is
turned on hard, resulting in too much current. On the other hand,
balanced resistances between each side and ground might not cause any
problem other than the circuit not working correctly.

Fred


The power amps always survive . In the process of exploring suspect caps etc
and turning over the pcb, the spade-connector for this 0V connection came
off the pcb spade. Looking under x30 on the spade and what I can see of the
line spade-socket, I can see no sputtering or smoke trails or anything
suggestive of a problem there.
I'm aware that a valve output matching transformer working hard and there is
a break in the speaker wire/connection /voice coil then enough voltage can
be induced in the primary side to knock out the output valves and weld turns
on the primary. But I do not know if similar in a mains transformer would
give enough current , from the energy stored in the inductance , to throw
back enough current , at over the mains voltage , to knock out the mains
fuse.