# ZW rectifier replacement



## plandis (Oct 5, 2011)

I got my hands on a 275wtt ZW. clean, tight, smooth- however, the whistle doesn't work on ether side. pretty sure from what I've read that some new style high capacity stud mount diodes are on order. I was reading up on this subject on this and other forums and found some discussion on the use of 12v ZENERs. Gunny- I saw where you were going to give these a try but I can see where you reported back the success (or failure). Should I give these a try instead of simple diodes??


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## BigAl56 (Dec 14, 2011)

*1N1183R*

http://www.digikey.com/scripts/DkSearch/dksus.dll?lang=en&keywords=1n1183r&WT.srch=1


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## servoguy (Jul 10, 2010)

This diode will work, but it is definitely an overkill at 35 amps.

For all you non-electrical engineers, the diode voltage rating is the maximum voltage that the diode can handle without going into reverse breakdown. They are not like batteries. So for this application, the 1N1183R that areizman suggests is a good choice as it has a 50 volt reverse breakdown voltage.


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## BigAl56 (Dec 14, 2011)

The 1N1183R is definitely overkill but it installs easily into the existing mounting hole. It's like it was made for the ZW. It also has excellent heat dissipation so if your kid wants to insistently blow the whistle the diode will not fail.


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## gunrunnerjohn (Nov 10, 2010)

There's something to be said for PnP.


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## BigAl56 (Dec 14, 2011)

Looks like Digikey is out of the 1N1184R stud diodes. You can use one in the same family of higher voltage with no problem.


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## plandis (Oct 5, 2011)

mouser has them. I was asking about a ZENER (12v) in this application.

http://www.tranz4mr.com/site/ZW_Whistle_Diodes.html

this is a good write up on the "how-to" but I was hoping to get Gunny to chime in on the use of a 12 v zener. I found some forum discussion about this on another site (that gunny was going to test it out.) in 2011 I think, I didn't save it but gunny said he had some ordered and would report back on the performance once he got them. 
John-?


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## gunrunnerjohn (Nov 10, 2010)

I've heard good things about using the Zener, and I even bought a couple. However, after getting all my brick supplies, I didn't really have a use for the ZW's. I sold both of them, so I now have two surplus Zener diodes that I'll probably never use.


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## servoguy (Jul 10, 2010)

You should NOT use a zener diode for the whistle control. A conventional silicon diode should be used.


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## plandis (Oct 5, 2011)

servoguy said:


> You should NOT use a zener diode for the whistle control. A conventional silicon diode should be used.



this is where I got that crazy idea:

"OGR member Dave Borgman suggested using zener diodes. They are
installed in place of the disc as the silicon post diodes are. However the
whistle resistor wire is disconnected & will now not be used. That's the white
fuzzy wire bonded to the bottom corner of the rectifier bracket. (or the
resistor on the fiber plate on ZW R). The zener is # 1N311B 50w 12v. "

I am going to give them a try. John- do you want to keep those zeners in your spare parts drawer? I have a couple ordered but if this works out, I'd like to pick up another ZW after the holidays and have a ZW for my boy's layout.


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## gunrunnerjohn (Nov 10, 2010)

servoguy said:


> You should NOT use a zener diode for the whistle control. A conventional silicon diode should be used.


That's not necessarily true. If you run modern electronics stuff in conventional mode, the Zener diode offers the advantage of not speeding up the locomotive when you activate the whistle. Many have done this successfully, so it's obviously a workable solution.


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## servoguy (Jul 10, 2010)

I think I can believe the Zener would work ok for an electronic whistle. However, for a post war whistle the lack of increased voltage would probably cause the train to stop when whistle is operated. A compromise might be to use a Zener with a lower voltage.


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## gunrunnerjohn (Nov 10, 2010)

Actually, the folks that have installed the Zener diode have reported that it works well for both modern and PW whistles. I don't currently have any conventional PW stuff to test, so I can't really say.


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## plandis (Oct 5, 2011)

actually, I did the zener upgrade on my post war ZW. works great! on all post ware and modern sound controls!


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## gunrunnerjohn (Nov 10, 2010)

And an actual user report!


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## sjm9911 (Dec 20, 2012)

Good stuff to know.


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## bowtieman427 (Jan 8, 2014)

I Something I noticed do NOT thinks it is a big issue for this purpose but would like to check. 
1. Diode VS-1N1183R is Cathode to case ? = Belll function A or D center U outside ? 
2. Diode 1N1190AR is Anode to case ? = Whistle function A or D Center U outside ? 

I am curious I just added Diodes to ZW-250 during restore. I believe Cathode to case diode was used and whistle will NOT work unless I hook up U to center rail and A or D to outside rail. To me this is less Ideal. When I have A or D on center and U on outside I get the bell working on more modern MTH engines no issues. If I reverce polarities I get whistle which makes sence. 
I have not measured or looked with a scope U looks to be a floating common when redid the ZW. Is there any forseeable issues having it wired U on center and A or D on the outside ? 

Any others experience this ?


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## BigAl56 (Dec 14, 2011)

For the 1n1183 series rectifiers the R suffix designates Anode to case.

http://www.vishay.com/docs/93492/1n1183.pdf

For older PW engines polarity did not matter so an 1183 of either type will blow a whistle. 
In the modern era polarity does matter and if you use a plain 1N1183 diode instead of an 1183R then yes, the Bell will ring instead of the Whistle.

I made the same mistake when I did my first upgrade. Fortunately I ordered both 1183 and 1183R rectifiers and learned which one worked by trial an error. I also have discovered while the 1183 is harder to come by the 1184R is more common and usually in stock


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