[Amps] Microwave Oven Autopsy

[Will Matney]

Marv,

Did you check to see if one of the windings was connected to the core, and if the core had a shunt in it? That is what most have that I've seen. Another thing that really ticks me about their manufacture, and a few other transformers too, is they weld the lams together. They put a weld right down one side of the lams, front to back, one bead about 1/4" wide. That makes them a bit*h to use for a rewind. A person with a mill, or be good with a disc grinder can remove the weld. Also, the shunt needs to be driven out with a hammer. This is really good though as it gives you more vertical window area for a new coil. What gets me though is why weld them and still use screws to hold the lams together?

Best,

Will

*********** REPLY SEPARATOR  ***********

On 3/12/06 at 11:57 PM wc6w at juno.com wrote:

>QST
>  Yesterday, I acquired a 2004 vintage Sharp microwave oven, from the
>"alley exchange", which was light (weightwise) enough that I thought it
>might contain a switching power supply.
>
>  Upon examining the unit, I found that the incredible lightness was due
>to its construction with frame metal of soda can thickness, and that it
>contained a conventional transformer manufactured by one Digital Power
>Communications Co, Ltd.  
>
>  There was an article in QEX about 10 years ago that discussed the use of
>these microwave oven transformers in plate power supplies.  It advised
>against using them in a conventional full wave bridge but, rather used
>them in an unorthodox half wave connection.
>
>  Examining the transformer at hand, it appeared that the insulation was
>uniform over the full length of the secondary.
>
>  I disconnected the "low side" secondary lead from the frame and
>hi-potted the secondary (also the primary just for science...) up to 4KV,
>referenced to the frame, with zero leakage.  
>
>  This suggests that one of these transformers might be employed in a
>"normal" connection for a low voltage (2500V) KW input amplifier.   Or a
>pair of identical units in parallel for a 2KW input amp.   
>
>  Caution, this suggestion MAY NOT hold true for other makers of this
>style of transformer.  
>
>73 & Good afternoon,
>   Marv WC6W  
>
>
>P.S. -- The magnets from the magnetron assembly make great refrigerator
>magnets!
>
>
>
>
>
>*
>
>
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