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In-Reply-To: <4D9A146C.25841.206191E@mike.dennison.ntlworld.com>
References: <4D9A146C.25841.206191E@mike.dennison.ntlworld.com>
Date: Mon, 4 Apr 2011 14:20:51 -0400
Message-ID: <BANLkTin5Cqa30bCch060R-+KR_z+h7Ev7w@mail.gmail.com>
From: Warren Ziegler <wd2xgj@gmail.com>
To: rsgb_lf_group@blacksheep.org
Cc: Mike Dennison <mike.dennison@ntlworld.com>
DomainKey-Status: good (testing) 
Subject: Re: LF: Decca faulty transformer?
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Mike,

    I had this fault, I believe that it is not uncommon.
It can be caused by a nearby lightning strike or by severe mis-tuning
in either case a short develops due to a voltage breakdown of the
insulation.
While the dc resistance is quite low, the inductance is substantial (I
can check and e-mail the proper value later if you'd like), I would
recommend measuring the inductance.
The core is potted in epoxy or similar material, I think it would be
difficult to rewind but I haven't tried.

--=20
73 Warren K2ORS
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XGJ
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WD2XSH/23
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XEB/2
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 WE2XGR/1




On Mon, Apr 4, 2011 at 1:56 PM, Mike Dennison
<mike.dennison@ntlworld.com> wrote:
> I have a fault on my Decca 5501 LF transmitter. It appears that the
> main output transformer / combiner is faulty. Each Tx module takes
> current when connected to the transformer, even when the output is
> disconnected. And there is no power out of the transformer.
>
> I have some questions:
>
> According to the the circuit diagram, the transformer's output
> winding has a 3.3nF capacitor across it. However, it seems to be
> invisible! Does anyone know where it is? Is it inside the pot core?
>
> Does anyone have a spare transformer for sale?
>
> Has anyone had a similar fault?
>
> Is it difficult to disassemble the transformer?
>
> It is very difficult to test for shorted turns because the resistance
> is extremely low.
>
> Any ideas?
>
> Mike, G3XDV
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
>
>