P-TF22798 PT orange wire?? &n

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mrr3000gt
I only work on Fender's
Posts: 585
(5/25/05 5:39 pm)
Reply   P-TF22798 PT orange wire??
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I have a power transformer (P-TF22798 from CE Distro) a customer has me putting into his AB763 Im building.

The schemo CE Distro sent him shows an organge wire called ground (I assumed this was the PT CT ground).

Then there are two wires RED/GREEN and RED/YELLOW. Im sure the actual CT for this transformer is the RED/YELLOW, but the schemo says "50v bias red/yellow to red/green".

Does this mean the RED/YELLOW is the CT and the RED/GREEN is the bias wire? In the Hoffman diagram a RED/YELLOW wire is shown for the CT and the bias wire is a RED/BLUE (this transformer does not have a RED/BLUE).

The orange wire in the P-TF22798 schemo I have is on the same side as the BLACK&BLACK (primaries in). What does this orange wire do? How many grounds can a transformer have?

This one has:
1) Orange wire marked for 'ground'
2) RED/YELLOW (normal CT on the secondaries?)
3) GREEN/WHITE CT for heaters

Why would the primary have a ground and the secondary be CT'd?

If someone can help, Im in the middle of wiring the power section and need to know!

Thanks,


 
PHATamps
I only work on tube amps
Posts: 486
(5/25/05 6:06 pm)
Reply   Re: P-TF22798 PT orange wire??
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 The orange wire is used to ground the Faraday shield, which is the copper shield you should see wrapped around the tranny.

The following is exerpted from: rgrace.org/146/157egrav2.html

"The field that exists between two conductors of differing electric potential can be screened or shielded in a given space by enclosing that space with a conductive material. Michael Faraday was the first person to note this effect and the shield is commonly called a faraday shield or cage... Modern transformers take advantage of this by introducing a faraday shield between the primary and secondary windings. Electrical noise in the primary winding is shielded from the secondary winding while magnetic induction between the windings is unaffected."
 
Craigzbrand
Senior tube assistant
Posts: 133
(5/25/05 6:16 pm)
Reply   Re: P-TF22798 PT orange wire??
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 It's probably just a shield, and it is not necessary to use it, but can be grounded. As long as you get no resistance value or continuity between orange and any of the other wires, it won't hurt anything to ground it.

As far as the red/green, this is simply a tap off one side of the high voltage winding. In other words if you read VAC between these two wires (red/grn and red/yell) you should get 50v.

It sounds like you've already done so, but if you want to verify HV winding CT, measure resistance between the two HV red wires, then measure between one red wire and the red/yellow, which should be half of your first reading. You should get roughly the same reading between the red/yellow and the other red.

I'd go with the schematic that came with the PT, rather than one you got from another source.

Take care - CraigB
 
RMS
Hey get your own solder
Posts: 218
(5/25/05 6:22 pm)
Reply   Re: P-TF22798 PT orange wire??
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 I have to agree with all of the above. Not to get of topic though but stragly that CE distrobution web site looks alot like Tubesandmore ??
 
GroundhogKen
Moderator
Posts: 2782
(5/25/05 6:27 pm)
Reply   Re: P-TF22798 PT orange wire??
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 Tubesandmore and CEdistribution are the same thing.

Tubesandmore is the retail branch and CE Dist is the wholesaler.


Ken


 
mrr3000gt
I only work on Fender's
Posts: 586
(5/25/05 7:27 pm)
Reply   Re: P-TF22798 PT orange wire??
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 Again, thanks all. Just when I start to think Im getting to be an expert at this stuff, I get a lesson that takes me back to the rudimentries.

I got a total of 3 AB763s to build, and only have about a dozen 5F6As I have built to compare the AB763 to.

 
 
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