[Boatanchors] Comet Pro Trasformer Went South

[GARY BROWN]

Filaments almost always fail by being shorted, not open. Filament windings 
use a heavy wire and it would take allot of current to melt them into an 
open condition. Most power transformers have the filament windings wound 
over the hv windings. When the hv winding is under an overload condition, it 
tends to heat the filament windings to a point that they become shorted.
Regards,
Gary
----- Original Message ----- 
From: "Bill Cromwell" <wrcromwell at gmail.com>
To: <hwhall at compuserve.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Monday, July 15, 2013 6:48 AM
Subject: Re: [Boatanchors] Comet Pro Trasformer Went South


> On 07/14/2013 10:31 PM, hwhall at compuserve.com wrote:
>> If it were my next move, I'd disconnect all but the xfmr's primary and 
>> apply power. If the transformer doesn't get hot then you know you've a 
>> problem somewhere in the rcvr that is overloading the xfmr. If it gets 
>> hot just running by itself, you know the xfmr has windings gone bad such 
>> as shorted internally.  The resistance mismatch between the two rectifier 
>> plate leads (112 ohms and 82 ohms) seems to suggest a short on the lower 
>> resistance side. Ideally they would be almost the same resisitance. (Hope 
>> I'm wrong though!!)
>>
>> Wayne
>> WB4OGM
>>
>>
>
> Hi,
>
> He could lift one of the filament leads from the transformer to complete;y 
> isolate the primary (or pull all the tubes. He already isolated the high 
> voltage side. It does sound like the transformer is toast (but maybe not. 
> Smoke and aroma from a transformer are not good omens. Best to find out 
> why before installing another transformer.  Sometimes a filament does fail 
> shorted even though most of them fail open.
>
> 73,
>
> Bill  KU8H
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