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Date: Mon, 4 Apr 2011 14:45:06 -0400
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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 just measured a known good Decca output transformer with a Peak
Atlas LCR meter.
The 3.2mH is correct for the monitor winding, the other windings
should be a bit above 106uH each (I got values between 106.4 and 106.8
uH)
--=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 2:34 PM, Mike Dennison
<mike.dennison@ntlworld.com> wrote:
> Thanks for the suggestion Andy. I did that already using an Atlas LCR
> meter
> (one of the best bits of test gear I ever bought), but didn't believe
> the result.
>
> It showed what looked to me like very low inductance, some 1.3uH on
> the
> =A0'primaries' and 3.2uH on the secondary. The 'monitor' winding is
> much higher
> =A0than this. Would a single shorted turn make all of the inductances
> low?
> The Atlas declined to measure the DC resistances as they were too
> low.
>
> Mike
> =3D=3D=3D=3D
>
>> Disconnect all windings and measure the inductance. =A0 If the
>> transformer is OK, the L will be high - with Xl many times the
>> operating impedance. =A0 A shorted turn - which is what it looks as if
>> you may have - will drastically lower L to a value that should be
>> evident
>>
>> Andy
>> www.g4jnt.com
>>
>>
>>
>> On 4 April 2011 18:56, 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 > > >
>>
>
>
>
>