DOH! Lighted Marshall power switch got me

[Randall]

I replaced a dead green lighted power switch in a VHT amp with the red lighted one CE Dist sells for Marshall replacements. I wired it the same as the original, but was left scratching my head when I discovered the light stayed on even with the switch in the off position. It wasn't until I swapped the upper and lower wires that it worked correctly. So apparently the two switches are wired differently. Easy enough once I figured it out, but it did catch me at a loss for a bit. Anyone else ever get fooled by this?

[drewl]

Guilty.
Especially with the older five wire switch converting to the newer 4 wire.

There's a diagram floating around for the conversion.

[Randall]

I think the conversion is simply to lose the fifth wire as not needed?

[Enzo]

There is no standard. Some have four posts for DPST, and a neon is wired between two of the posts. The mains goes to the other two posts, while the neon ones go on the switched side, otherwise you have what you found out. other DPST switches have six posts, four are the regular switch contacts, and the extra two are for the internal neon. And ther are versions with the neon wired to one post, which should be on the switched side, and an extra terminal for neutral. There are SPST switches like that too, where two posts are the switch, and the extra is the other end of the bulb.

You can also use some of these other ways. In the one wher the neon is internally wired across a pair of posts, it pretty mkuch is just an on light. But the ones with separate posts can be used as indicators. Like the neon comes on when power is on, unless it is in a fault condition, and then maybe the bulb blinks. Or a switch could be lit to indicate a thermal cutout. That sort of thing controled from the circuit.