Line voltage bucking transformer question

[eddie25]

I finally got around to trying a 12.6V, 4A transformer as a line voltage bucker for an old 40 watt Epiphone combo to get to 110VAC and I'm happy to say it worked great under my first test. The only issue is that I realized the transformer stays on and warm when the power chord is plugged in, whether the amp is on or not.

For that reason, is this technique a bad idea as a permanent install? I was really wanting to wire it up all nice and mount it in the cab, what do you guys think?

[Sazafraz]

Could always but it on its own switch

[xtian]

Why not apply AC using the same power switch as the PT?

[eddie25]

Why not apply AC using the same power switch as the PT?

Do you mean putting the bucking transformer after the power switch? That makes sense, it just adds major layout issues, since I would then need two different sets of power chords running into the amp.

Maybe I just need to make it in an external box and add a switch and fuse.

[xtian]

What? Aren't you feeding the output of the bucking tranny into the PT? Why two power cables?

http://sound.westhost.com/articles/buck-xfmr.htm

[eddie25]

Yeah, I'm not really sure what you meant in your first post. I am feeding the AC into the same switch as the PT.

[eddie25]

Gonna leave it plugged in for a while and see what happens.

I think I may have felt the temp of the bucking transformer to soon after playing the amp so it was still warm from that. Without drawing current it shouldn't heat up much right?

[xtian]

Sorry, Eddie, my first post was before I looked at the schemo. I have never implemented this. Just flapping my keys because no one else is!

[Suzanne]

NEVER sounds like a challenge.

[JazzGuitarGimp]

You are probably aware of this: if you are in the US, structures are wired with a split phase scenario. From the breaker panel, some circuits are wired from the A-phase and some are wired from the B-phase. The two phases are 180 degrees out of phase, and if you measure between the hot legs between the A-phase and the B-phase, you've got 240 volts. So, if you are using two power cords to implement the bucking transformer, it's conceivable you could inadvertantly apply 240V to your amp. It's probably not real likely if you are plugging both cords into the same outlet. I am pretty sure the building code doesn't allow for one phase in the top outlet, and the other phase in the bottom outlet. But stranger things have happened.

[Colossal]

NEVER sounds like a challenge.

MODERATOR: clean up on aisle Spambot please. "Suzanne" needs to go away.

[eddie25]

Well, hours later and the bucking transformer is very warm to almost hot without the amp ever being turned on. Pretty bummed out about this because instead of WAY over voltage, the amp was perfect voltage. I bet it would be safe with a fuse, but I wanted to give this amp away to someone in need and I don't feel great having a hot tranny in a wood cab the whole time the amp is plugged in. Also not to jazzed about an external box. Live and learn.

[xtian]

Go easy on Suzanne. She quoted me verbatim in a other post, making her my first official disciple.

[martin manning]

Don't know what this amp looks like, but is there room to mount the bucking tranny on the existing chassis? If not you could put it in a small box and mount it inside the cab. Either way, just break the connections to the amp's PT and wire it in between.

[LeftyStrat]

Go easy on Suzanne. She quoted me verbatim in a other post, making her my first official disciple.

And she quoted my current sig. I think she likes shoes.