[Amps] Core wrapping?

[Carl]

For the slight extra tape expense it pays to be conservative in your 
approach.

Teflon still cold flows as it has done for decades. I just got thru with 
an Alpha 76PA repair were the Teflon sleeved buss wire arced thru the 
single tape wrap core. Not a pretty sight and it also took out two of 
the 8874's.

Circulating voltages in some tank circuits can easily exceed 2-4X the 
DC.

The replacement I built used silver plated Teflon insulated stranded 
wire inside another Teflon sleeve and plenty of tape. There is a reason 
the wire manufacturers use silver plated wire with Teflon.

Carl
KM1H



----- Original Message ----- 
From: "alexeban" <alexeban at gmail.com>
To: "'TMorton'" <cx7tt at 4email.net>; <amps at contesting.com>
Sent: Sunday, November 16, 2008 10:00 AM
Subject: Re: [Amps] Core wrapping?


> ...first, core wrapping stems from the time when cores were unpainted.
> Indiana General were notorious!
> Second, the wrapping was done in order to avoid arcing to the core at 
> a time
> when wire insulation was not at its best. Today Teflon covered or 
> Formvar
> wire can withstand 2-3 kV quite easily.
> What remains is just protection from the abrasive corners of the cores 
> and a
> little cushioning to absorb wire deformations resulting from 
> tightening the
> assembly to its support. wrapping each core separately in a stack 
> doesn't do
> a thing for the whole.
> Alex 4Z5KS
>
> SunWolf
> "Jesus, come get your kids, they're tearing up my Mother's backyard!"
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] 
> On
> Behalf Of TMorton
> Sent: Wednesday, November 12, 2008 7:32 PM
> To: amps at contesting.com
> Subject: [Amps] Core wrapping?
>
> Am in the process of building up a 8877 amp and now working on the 
> Tank
> Circuit coils....I am pretty much following the ARRL Handbook 2006 for
> L4 and L3 (160,80m). to handle the high power, I am using 3x T300-2
> cores with #10 Teflon silver wire and 3x T225-2 cores w/teflon, etc. 
> My
> question is when 'stacking' the cores do I stack the 3 cores then wrap
> the fiberglass tape around them OR do I individually wrap each of the 
> 3
> cores with the glass tape then do an additional wrap over the 3 of 
> them
> together?
> Tnx
> 73
> Tom
> CX7TT
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