Diode in KW problem, need help

Eric SareskyOGR Forum Member

I replaced the rectifier disc in a PW KW to correct the non-working whistle. It would only work with the lever half way, so I knew I wasn't getting the holding DC for the relay. After I installed the diode, the whistle works perfect but I have a new problem. When I move the lever, I get an arc on the finger contacts at the half-way position, no arc as the lever goes to the full position. This happens with or without the tender on the track, it happens with NOTHING connected to ANY of the KW's outputs. After moving the lever just a dozen times, I see arc marks on the contacts and one time the lever even stuck. I will post a picture of how I installed the diode Monday morning. This link is the diode I purchased : diode
There is more clearence between the coil and the diode then the picture shows and the arm doesn't hit either. Help anyone?

12/4/1110:58 PM

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rrmanOGR Forum Member

What is that heatsink metal strap connected to? Is Diode insulated from the heatsink or is the heatsink metal not attached to any other metallic structure. I wonder if the contact is shorting out diode or creating a short via the diode.

12/5/116:15 PM

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YardmasterOGR Forum Member DIGITAL SUBSCRIBER

What was the number of the rectifier you installed?

Make sure you installed the "anode to case" style rectifier!

Let us know.

12/5/1110:16 PM

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Eric SareskyOGR Forum Member

quote:
Originally posted by Yardmaster:
What was the number of the rectifier you installed?

Make sure you installed the "anode to case" style rectifier!

Let us know.

It's a Ruttonsha 16 FLR 60. Yes the case is the anode according to the data sheet.
data sheet

12/6/111:05 AM

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Eric SareskyOGR Forum Member

quote:
Originally posted by rrman:
What is that heatsink metal strap connected to? Is Diode insulated from the heatsink or is the heatsink metal not attached to any other metallic structure. I wonder if the contact is shorting out diode or creating a short via the diode.

It the original bracket that held the rectifier disc. No, it's not insulated but is installed as per the instructions.

12/6/111:08 AM

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nvocc5OGR Forum Member

I had a same problem with my install. Sometime you have no problem and sometime you have an a arc. The way I solved it was to place liquid tape on the diode and the brass strip that was closest to the coil. It is messy but it worked and I do not have the arc problem anymore.

5/24/1411:26 PM

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TrainLarryOGR Forum Member

The arcing is probably caused by a higher current being generated with the new diode as opposed to the old disc rectifier. You may wish to try installing a capacitor across the contacts to minimize the arcing. Try using a 1000microfarad@100volts to start with.

Larry

5/25/141:52 AM

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