Twist PT primaries?

schmee

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Do you? should you? If you had a situation where the Green AC ground ran parallel to the primaries, would you include it in the twist too?
 

dsutton24

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I do just as a matter of lead dress. There may be a tiny theoretical advantage from a noise suppression standpoint, but transformers do that anyway. I guess I do it because it can't hurt :)
 

Uncle Daddy

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Makes for a tidy amp. Years ago I had a pal that used to paint the insides of his model aircraft kits- now I get it!

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schmee

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👍 Just thinking about the Champ I just finished that has some hum. I used a tranny I had laying around that was an export model with wires at both ends, so I jury rigged it like this, the primary wires and ground wire twisted come into the chassis through a hole and alongside the PT. Was wondering if that caused some hum.
It's weird; hums with the guitar volume in the mid range, but not at 10 or at 0. That guitar doesn't hum at all with other amps.


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2L man

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It's weird; hums with the guitar volume in the mid range, but not at 10 or at 0. That guitar doesn't hum at all with other amps.
This is interesting! Instrument cable is symmetrical and perhaps it can cancel some noise? Obviously when guitar Vol pot is in the middle the pickup is not symmetrical source? I try to think this? Perhaps there already is an answer somewhere in internet?

It looks rather simple mod to make return currents flow in single bus or few wires? Definitely start construct your future amps properly straight away ;)
 

King Fan

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Hmm, @schmee, interesting hum problem. Do you have a photo of this PT? This installation? I can't quite picture why the ground wire has to do with the PT. Maybe just me -- I'm a visual guy.
 

schmee

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Hmm, @schmee, interesting hum problem. Do you have a photo of this PT? This installation? I can't quite picture why the ground wire has to do with the PT. Maybe just me -- I'm a visual guy.

Maybe I misunderstood. Does your PT has an electrostatic shield wire? Is that what you're calling ground?
Sorry, totally brain dead when I wrote that. :lol: I meant the black COMMON wire, not ground. This tranny has 220, 230, 240, 120, 125 and 100v options! Everything but the 120, 125 and Common I clipped off and protected inside the bell.
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Phrygian77

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I'm talking about the green AC Ground.

Rereading your post it sounds like you're talking about the routing of wires coming from the transformer. Since power transformers don't have an 'AC ground' wire, this is where I'm confused. Sometimes they have a separate electrostatic shield which would connect to ground. There's no ground on the primary side, and secondaries and their center taps may or may not be directly grounded depending on the configuration. You wouldn't call those 'ground wires' regardless.

Edit: I see now that you updated with a post about this.
 

schmee

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Rereading your post it sounds like you're talking about the routing of wires coming from the transformer. Since power transformers don't have an 'AC ground' wire, this is where I'm confused. Sometimes they have a separate electrostatic shield which would connect to ground. There's no ground on the primary side, and secondaries and their center taps may or may not be directly grounded depending on the configuration. You wouldn't call those 'ground wires' regardless.

Edit: I see now that you updated with a post about this.
See post #13, total brain fart using the word "ground". Was talking about the Common.

In post #1 I WAS talking about the green AC wire but just in a theoretical situation regarding twisting.
 

Phrygian77

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@schmee I would normally just bundle up those extra primary wires (and unused secondary wires) and tuck them away instead of clipping them off altogether. There's not any current flowing to produce fields and you don't really need to worry about them picking fields up either.
 

schmee

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@schmee I would normally just bundle up those extra primary wires (and unused secondary wires) and tuck them away instead of clipping them off altogether. There's not any current flowing to produce fields and you don't really need to worry about them picking fields up either.
Yeah, there are so many wires on this thing... sometimes a bargain isn't such a bargain! 17 wires! I dont really think the PT is my hum issue, but need to get into it. The power tube is only about 1/2" max from the speaker magnet. Maybe that's it. Although it wasn't an issue when this chassis was a Princeton clone. I wonder if Cathode bias would be effected more by the magnet..... Next test will be to remove the chassis and play it away from the speaker.
 

schmee

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👍 Just thinking about the Champ I just finished that has some hum. I used a tranny I had laying around that was an export model with wires at both ends, so I jury rigged it like this, the primary wires and ground wire twisted come into the chassis through a hole and alongside the PT. Was wondering if that caused some hum.
It's weird; hums with the guitar volume in the mid range, but not at 10 or at 0. That guitar doesn't hum at all with other amps.
I guess I'm drifting my own thread!... UPDATE on the Champ hot rod clone:

So today I went out with the same guitar and tested the Champ+ again. No hum now.
I realized that during the first test, I was sitting right next to the amp on top of another amp.
It's weird how that guitar did hum the other day but my Strat didn't, but still, once I'm sitting 3 feet in front of the Champ+ there is no hum now.
So.... problem solved!
This champ+ clone has some tasty tone to it and seems much louder and meatier than the SF Champ I sold not long ago. Better tone... probably due to the bigger deeper cab and 12" speaker to some extent, but I did try different speaker setups with the old SF Champ. The bigger 14 watt Output Tranny seems to do a lot for a Champ circuit. Right now I'm not running the 6L6WGB I planned on running in there. But it's cleaner and louder with just that tranny.





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Bill Moore

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Glad you found it, I built a 5E3 for a friend last year, and fired it up on the chassis stand. It was on my work bench, (the kitchen table), and it had a hum! I quit for the night, but came back the next evening, plugged my Tele in, and -----no hum! I played a while, and my wife came through, and said "sounds pretty good, but you are going to ruin your eyes here in the dark", and turned on the light. I had forgotten that circuit was on a dimmer, and my Tele really doesn't like it!
 

King Fan

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Good for you. May not be relevant, but when I sit next to my 5E3 to twiddle the dials (an especially 5E3 thing) I gotta be careful to sit at the non-PT end... even with noiseless pickups.
 




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