oops..

[Lindz]

working too late tonight and got careless drilling a hole to mount the board

"why is this so hard to drill?" he thinks as he is not noticing he is drilling into the bottom of the OT.

I had 3 bolts and standoffs mounted on 3 corners of the board and was drilling the 4th through a hole in the board so it would line up, and did not notice it was sitting over the OT.. Duh! (headsmack)

Anyway I have drilled about 1/4" to 3/8" into the laminations with a 3/32" bit..

Any way to tell if it will short?

[Stevem]

It will still work fine, but if you had used a 3/8" bit it might have been a different story, and good thing it was not a filter you drilled into!

[Homebrew]

I guess you will have a more airy tone now

[Garthhog]

I did that to a 10H choke once (and only once). Unfortunately, the bit didn't stop at any laminates. It now sits on top of one of my workbenches as a constant reminder not to be an idiot. The upside? At least it wasn't an OT or PT...

[Zippy]

Any way to tell if it will short?

The correct test is a megger. It tests for insulation breakdown.

[Structo]

Is that like a high pot?

[pdf64]

The lams are made from high resistance steel and are insulated from each other, I think idea being to prevent eddy currents, which would increase losses.
Any burrs on the laminations may result in the laminations shorting together.
So consider attempting to make an assessment of whether that might be the case.

[Zippy]

Is that like a high pot?

Same, same - "Megger" is the manufacturer of the most commonly used test unit.

It will apply about 10kV between the windings and ground.

[pdf64]

I think that a standard megger uses about 1 to 2KVdc and measures leakage current, whereas a full hi-pot tester uses >2kVac, so presents a more rigorous procedure, especially as it may be required to sustain low leakage for >30 seconds.

[Zippy]

Hmm, that could be more correct. They say the memory is the second thing to go...

I used to be a navy electrician ('70s) and used the ol' hand crank megger for motors and wire runs, and the larger units for testing LARGE generators. !-2 kV sounds mo' better for a unit that operates in the several hundreds of volts range.