Tony,
How do you think a pair of the MOT's would hold up? I've been planning
to build a power supply like the one you put together, only using a pair
of trannys in parallel. This would be set up to drive a pair of GI7b's,
hopefully.... Been in the planning stages for a couple of years now, hi hi.
73
Dan
Tony King - W4ZT wrote:
> I used a transformer almost identical to this one in my GS-35B tube
> tester <http://tester.gs35b.com>.
>
> It has the welds nicely done connecting all the lams together. Even
> after driving the shunts out the transformer is quite lossy. Even with
> no load it gets quite warm when you apply primary voltage. I did drive
> the magnetic shunts out. They were also paper wrapped and were fairly
> easy to drive out.
>
> This transformer had one end of the secondary soldered to a lug that was
> under a screw driven straight into a hole in the lams. I took that
> connection loose, slipped a short length of Teflon tube over the loose
> wire and then soldered it to a solder lug that I put under the original
> screw. It put out 2200 VAC no load and with a full wave bridge produced
> 3000 VDC with 56uF capacitance. Unfortunately, the voltage dropped
> quiet a lot under load. With 450 mA load, the output HV will drop to
> about 2150 VDC. Not a big deal for what I'm doing but not so good for
> an amp.
>
> 73, Tony W4ZT
>
>
> wc6w@juno.com wrote:
>
>> Hi Will,
>> This one has four 1/8" wide welds down the opposing sides. And yes, it
>> has the shunts but, they are encased in transformer paper so, I'd guess that
>> they could be easily driven out without disturbing anything else. No screws
>> what so ever. The lams are even welded to the mounting frame in four spots.
>> The "cold" end of the secondary was soldered to a lug which was riveted to
>> the lams -- I necessarily disconnected that wire for the hi-pot check.
>>
>> It looks like it's wound at about 1 turn per volt. As the core wouldn't
>> practically dissassmble, the only easy rewind would be for a filament
>> transformer. The secondary could be sliced out by a careful guy and rewound
>> with a bundle of large wires in parallel making a KW filament transformer...
>> for say a 4CX5000/10000? Or twenty 813's? :-)
>>
>> 73 & Good afternoon,
>> Marv WC6W
>>
>> **********************************
>>
>>
>> -- "Will Matney" <craxd1@verizon.net> wrote:
>> 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@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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