From: "Mike Dennison" <mike.dennison@ntlworld.com>
To: rsgb_lf_group@blacksheep.org
Date: Mon, 04 Apr 2011 19:34:00 +0100
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Subject: Re: LF: Decca faulty transformer?
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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
 'primaries' and 3.2uH on the secondary. The 'monitor' winding is 
much higher
 than 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
====

> Disconnect all windings and measure the inductance.   If the
> transformer is OK, the L will be high - with Xl many times the
> operating impedance.   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 > ========== > > >
>