[Hammarlund] Comet Pro Trasformer Went South

[Kenneth G. Gordon]

Transformer is internally shorted. Get it rewound.

Ken W7EKB

On 14 Jul 2013 at 18:06, Joe Connor wrote:

> 
> 
> I picked up a Hammarlund Comet Pro at a hamfest today. I changed the
> filter caps, ran it on a variac at about 105V and got it playing. Then
> the power transformer went. I want to go through my diagnosis just to
> make sure I've eliminated any possibilities other than the power
> transformer. I also want to get any ideas anyone may have on a
> replacement.
> 
> Diagnosis: The xformer started smoking with the unmistakable bad odor.
> B+ dropped badly and the receiver stopped playing. I pulled the
> rectifier tube and the xformer still overheated. I replaced the
> rectifier and disconnected the lead from the rectifier to the first
> filter cap/filter choke and it still overheated. Resistance between
> the filaments on the rectifier socket (with the rectifier removed)
> measured 0.1 ohms. The plates on the rectifier socket measure 194
> ohms. Plate to ground measures 112 ohms and 82 ohms. I just want to
> make sure it's the power xformer. I have restored close to 100
> boatanchors and this is the first power xformer I've had go south. I
> guess I was living on borrowed time (or else replacement of filter
> caps before the initial fire-up really does avert a lot of
> disasters). 
> 
> Replacement: Any ideas on replacement?  This set uses tubes with 2.5V
> filaments so I'm sure my options will be limited. This set is pretty
> beat up so I'm not sure how much I want to spend. On the other hand,
> without a new xformer, this set is just a big doorstop. There is space
> on the top of the chassis for a separate plate transformer, if
> something like that is possible.  Of course, if anyone has a junker
> laying around with a good xformer, I would be interested in buying it
> (along with a few other non-essential parts that are missing from
> mine)
> 
> As always, thanks for your help and guidance. 
> 
> 
> Joe Connor
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Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne