Metering Bias Blows Fuse

[gtto]

Strange thing happened. I was checking the bias on an amp. there are two test points r140 and r141. WHen testing one, no problem. When testing the other I got a spark as soon as the probe touched the resistor and the fuse blew. What would cause this?

[Jazz P Bass]

Not too sure what amp we are dealing with here.

Check the resistor that 'sparked'.
It may be open.
And that tube may be bad.

[Enzo]

Or you grounded off the high voltage and blew a fuse.