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repairing the whistle controler on a kw.

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repairing the whistle controler on a kw.
Posted by Anonymous on Saturday, September 16, 2006 5:53 PM

Whats the best way to repair the whistle recitifer on a kw transformer? I would like to replace the recifier disk, but looking around there dosent seem to be a lot of room to install one of the big diods.

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Posted by Anonymous on Sunday, September 17, 2006 9:14 AM

Since no one else has responded, I'll take a shot at it.  I replaced the rectifier disk in my KW with one of those "big diodes,"  and cleaned up the contacts a little with denatured alcohol.

There isn't a lot of room to work,* and the job is not as easy as on a ZW, so I just used sufficient wire to allow the diode to hang all the way to the bottom of the transformer. I wrapped the daylights out of it with electrical tape, and stuck it to the base with some kind of semi-permanent adhesive -- I can't recall exactly what. It doesn't look like much on the inside, but it works like a champ.

* It is possible to get a KW apart, but I am very conservative about NOT dis-assembling anything held together with bent or twisted metal tabs, based on the likelihood of shearing them off. The KW is full of these tab-and-slot or bent metal assemblies and I recommend leaving them alone.

 

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Posted by Anonymous on Sunday, September 17, 2006 10:07 AM

Thats kind of what I was thinking about doing. I have some large shrink tube I can protect the diode with, I can solder some leeds off the diode, but not sure witch leed will go where. Looks like i also will only need one diode to make the repair?

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Posted by Anonymous on Sunday, September 17, 2006 10:22 AM
The end of the diode with the silver band around it gets connected to the metal bracket that the rectifier is on.  Unsolder the wire that is connected to the speednut on the front of the rectifier, and solder it to the other end of the diode.  Insulate the connections to finish the job.
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Posted by lionelsoni on Sunday, September 17, 2006 11:09 AM
The stripe that Jim mentions marks what is called the cathode.  If the diode is marked instead with the diode symbol, the arrowhead in the symbol points toward the cathode end.  If it is in a metal case with a threaded stud, the cathode is the case, unless the part number has an "R" at the end, for "reversed".

Bob Nelson

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Posted by Anonymous on Sunday, September 24, 2006 4:54 PM

Ok, I have the cover off the transformer, no wires are sodered to the disk, just a speed nut, and stud that goes though a brass strap behind the silver plate. there is some fiber washers to isolate the parts from touching each other. there is some wire thats wrapped around the silver bracket.

I have a 40 amp stud mount diode, anode to case.

The threaded stud gose to the brass strip, and the post with the hole gose to the silver bracket?

 

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Posted by lionelsoni on Sunday, September 24, 2006 6:38 PM
Don't lose or shorten that wire that's wrapped around.  It's the resistor in the whistle circuit.

Bob Nelson

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