[murphyv310]

Lamp limiters and variacs are for valve equipment and linear power supplies only.
NEVER for SMPS. Some sets service manuals would even tell you not to use a variac in the notes.

Another that blew up with them was the Tandberg CTV2 my foreman couldn't fix one after many attempts and it was returned to Tandberg, on return a label was attached with a warning about using a varaic. After he fixed many of them like the rest of us did with no further issues.