Music man 65 death cap

[tdlunsfo]

I have this guy on the bench and it's my first music man. I noticed it came from the factory with a a three prong cord and a death cap. I also notice the neutral is running through the fuses and power switch. I really don't feel comfortable letting this go out with a potential unsafe condition but not sure which way to go here. I assume at a minimum I need to either disconnect or replace the death cap with x/y rated. On this setup, are you all typically swapping the hot and neutral wires as well?

[g1]

Yes. Neutral direct to xfrmr, hot to fuse in that drawing.

[tdlunsfo]

Got it. Would you remove or replace death cap?

[The Dude]

I would remove it. You can't trust ground to actually be ground in a lot of venues.

[tdlunsfo]

Well, I wired as recommended and now the “Hi” setting lights up my dim bulb. After going through the fuses the black hot wire jumps down to the on/off switch pole. The throws are the yell/black back to the transformer (I assume this is some kind of center tap for the low switch) and the other throw is the Black hot back to the transformer. The white from the power cord is directly connected to the white on transformer. Gnd switch wires have been lifted. I have rewired many an amp just like this but I have never had one with a “lo” center tap. For some reason it doesn’t like the way I have it. Swapping it back to the switch being in the neutral leg and the dim bulb goes dim. I am missing something but can’t see it...

[SoulFetish]

According to the schematic, If you’re trying to fuse and switch out the hot, you should be connecting the neutral right to the black wire. (See bottom of transformer schematic drawing).
Then run the black hot wire to the fuses, then the fuses to the switch pole. The yellow black lead is actually the “high” setting.

[tdlunsfo]

10-4. I am going to disconnect the transformer and do some experimenting this morning. Will report back.

[tdlunsfo]

This works but am struggling to understand why. The resistance measurements on the primary indicate the yellow/black wire is a center tap. 4 ohms black to white. 2ohms either y/bl to wh or y/bl to bl. I just don't see why it would matter how it is connected but it does. Guess I need to see if I can find some documentation on a replacement transformer and see how it is wired internally. My fear is that down the road someone will open this amp and see a power cord neutral directly connected to a transformer black wire and get confused.

[SoulFetish]

This works but am struggling to understand why. The resistance measurements on the primary indicate the yellow/black wire is a center tap. 4 ohms black to white. 2ohms either y/bl to wh or y/bl to bl. I just don't see why it would matter how it is connected but it does. Guess I need to see if I can find some documentation on a replacement transformer and see how it is wired internally. My fear is that down the road someone will open this amp and see a power cord neutral directly connected to a transformer black wire and get confused.

Its not a centertap, because it’s off center and there are only two connections to the transformer at any given time, or its off. Look at the schematic at think about it in terms of turns ratio.
Transformer lead wire in the primary is insignificant in that it is not required to be compliant with mains wiring color code.
If you’re concerned leave a label inside the chassis explaining your changes

[tdlunsfo]

I see it now and I guess my resistance measurements threw me off. Then again, my meter is likely not accurate enough to measure it correctly.