ZW Whistle Diode Help

I keep thinking that maybe I should just buy a ZW-L....but then I see the prices and think maybe I should just buy a modern whistle button...lol

Did you try reversing the power leads to the track? Sounds like that may be why you ZW does not sound modern whistles.All my transformers now have the diode upgrade and all sound any whistle.

Rob

You may have purchased the wrong diode. For the whistle I believe you need anode to stud  (whistle)   not cathode to stud) bell.  I don't think reversing wires at the track will help.  You can still get the old rectifier disk.  It seemed to work just as well as the diode.  Fire away.

If the whistle button rings the bell now on your modern locos when the whistle blew before, the diode may have been installed backwards. Newer trains are DC polarity sensitive; one polarity blows the whistle and the other rings the bell. Postwar whistle relays are not polarity sensitive, so that is why your postwar whistles will work if the diode is installed backwards.

 

When a switch contacts are closed, there usually is an arc that is created, so that observation is normal.

 

When the whistle button is pressed on postwar transformers, a 5 volt increase in track power is applied to compensate for the extra load of the whistle motor, so what you observe is again normal.

 

Did you install a stud rectifier, or a plastic case axial lead rectifier?

 

Larry

Thanks guys, it is a stud rectifier, so I don't think I could have wired it wrong. I took the wire off the clip that held the whistle rectifier disc on, and soldered it to the little hole on the diode. The other end of the diode is bolted in the whistle rectifier disc's hole.

 

As for comments about changing polarity, since I don't have a modern plug on my transformer (my electrician father says it's still good, as the rubber is in great shape), could I just turn the plug 180 degrees to switch the polarity? My layout is wired with everything based on the outside rails going to the common side of the transformer, and I don't want to have to undo all that wiring for a test if I don't have to.

 

And as for buying the wrong diode, I hope not, since I bought four of them from the transformer guy at Allentown Spring Thaw, and they were listed as for whistles. I guess it's possible though.

 

Thanks for all the help so far guys!

Try playing around with switch position, and speed.  After I upgraded the diode on my KW, for my Bachmann horn, it will only work if I quickly bump the switch to the first position, no farther.  Air whistles are not a problem.

Switching the AC plug in the outlet will not change the DC polarity to the track. Instead, reverse the wiring to the track from the transformer. That should get the whistle to work on your newer engines again. It should not affect your postwar locos.

 

Larry

I just make an external one,shown here

 

LINK

 

Here it is automated with relays to blow at a crossing gate approach

 

LINK2

 

Dale H

Michael R,

    The man you want to talk to is O Gauge Jim (Jim Lawson) at the present time he is installing them in a 250 ZW for me, he knows his stuff about reworking transformers, especially ZW's & KW's.  Do an OGR Search for the thread or look in the for sale section for the ZW he is selling me.

PCRR/Dave

This problem comes up all the time with old transformers and electronic horns

and can motor engines. The transformer requires about a 5 amp load current

to produce enough DC off set to operate electronic horns. Can motors do not

draw enough current to generate enough DC off set so adding lighted cars

may increase the load enough to operated the horn.

 

A Zener diode replacement for the disc rectifier works the best.

 

An old VOM meter, with a pointer, set on the 10volt DC range will indicate about 5v when the horn button is operated if there is enough load current for the horn circuit

to work.

   

Gentlemen,

   After fully reworking the old ZW or KW internally, I also recommend the addition of Banana Plug Fittings, long ago I posted which type and how to add the female portion of the Banana Plugs, to the old ZW's & KW's.  If you do an OGR search I believe it will still come up.

These old ZW & KW transformers are still great stuff for running DCS and Legacy, just set them up correctly when doing it.  I plan on adding the Banana Plug female fittings to the 250 ZW I am getting from Jim.  They eliminate the messy close up wiring and the loosening of post nuts as the transformer is used, along with providing great electrical connections.

Enjoy your old ZW & KW transformers with your modern train layouts.

PCRR/Dave

Well, I switched the wires and the whistles blew in my low-end modern Lionel (starter set stuff). My TMCC engines still stop. So, I'm back to where I was, with a new diode. Would I be better off to get one of these?

 

http://www.ebay.com/itm/400868...e=STRK%3AMEBIDX%3AIT

 

Also, the fact of switching the wiring has my mind blown. I thought that you were supposed to put A-D to the center rail, and the outside rails to the common. My layout is wired that way, so if I do rely on these diodes, my layout's wiring needs to be rethought.

Michael R,

   Just have somebody like Jim install the diodes correctly in your ZW, the battery operated Lionel whistle activators are a pain, I do not recommend them, I have one it never ever gets used.

PCRR/Dave

I might just do that. I know there is a local guy who redoes them (but it's the guy I bought the diode from), but I'm not sure that I want to go that route.

Maybe my tax refund will go to a new ZW-L

Mike,

You are correct in stating how the ZW should be wired. The fact that the whistles in your newer trains operate properly with the transformer wires reversed seems to indicate that either the diode was wired improperly inside the ZW (unlikely), or possibly that the diode is not the proper one. The diode should be anode to case as seen here. If you have a cathode to case diode, then yes, the diode would put out the wrong polarity, even if it is wired correctly.

 

What is the number of the diode you have installed, so the specs can be checked?

 

Larry

Michael,

   The new ZW-L's are pretty pricy, and most times your old ZW will do the job required, in fact I just picked up another old 250 ZW to add to my power station.  However if you have the money the new ZW-L is a real nice transformer, the Z4K is also.  Remember you should definitely always over power your layouts, but depending on how big your layout actually is, the ZW-L might just be over kill.

PCRR/Dave

The studded rectifier is suppose to be anode to case.

The ones I use have the part # NTE 5991 on them and rated at 40 amp / 400 volt and when those are used up I will be switching over to the 40 amp / 600 volt 1N1190AR from All Electronics which others on the forum have recommended because of the higher voltage range.

 

I have been installing these for years and never had a problem as you are describing.

The only thing I can think of is you have the wrong one.

Yardmaster,

    I agree 100%, I do believe he has the wrong diode, or installed it incorrectly.  It's why I recommended he talk to O Gauge Jim.

PCRR/Dave

Well as they say, a picture is worth 1000 words.

 

Installed in my ZW

 

 

Here is another one that I bought from the same source (a man who repairs transformers and sells them at train shows)

 

 

 

Let me know what you guys think.

I'm no expert but by looking up your part #25F40 you have cathode to stud diode!

You should have a anode to stud! The part # should read 25FR40.

 

http://www.alliedelec.com/imag...TALIANA/70078701.pdf

 

Hopefully someone with more electrical knowledge will chime in to verify!

That is indeed a "normal" diode, not the reverse-polarity type that you need for compatibility with modern engines.  Many of the proper type have an "R" at the end of the part number to indicate the reversed polarity.  The diode symbol should point away from the stud, not toward it.

 

Get your money back from the diode vendor!

Compare the diode symbol on your diode in the last picture to the recommended replacement and you will see they are different. You indeed have the wrong diode.

 

The diode that you bought will work with older relay operated whistles and horns. That is probably why they are being sold. The vendor should know, or be informed, that the diode he sells will not operate modern equipment properly.

 

Larry

Thanks everyone! You have all just made my day! I will be messaging the vender, who like I said sells tables full of repaired transformers, and let him know. I will also order new ones from the link in TrainLarry's post above.

Mounting on a threaded, electrically isolated, block of aluminum, would supply a heat sink (you will likely need), and then once isolated, you could simply reverse the diodes connections. (Use a good thick "chuck", or a big heat sink from junk electronics).

 

 If one diode doesn't work, the voltage offset(amount used within the diode) might be a little too low(just under 1.5v), adding another form of resistance in series (like another diode), could increase the offset to a more acceptable level of 1.5V offset, or a bit more. I wonder if some boards look for the PW voltage boost. Some boards do have chopped, vs pure sine recognition issues too. Weavers I've had here, were totally dependent on one wave type, I forget which.

 

My issues I shrug through because I can...

 The big pre-war whistle boxes eat 5 volts, and my "new" whistles ignore them on newer "conventional" locos. TMCC losses its mind like its midnight on New Years Eve.

Pre & Post War, it works fine.

 

My AF 18b, no whistle, wont work the pre war boxes right enough to work anything.

TMCC likes to party on this power rig too. With or without a controller hooked up.

 

 The "little buttons" don't have enough "guts" to deliver big power, and still stay cool enough. They only work the very best of my old tenders, a Sound of Steam, and one TMCC (e33 Virg.).

 I own 5 1033's, they all run PW ok. Only two get electronics working, the SoS, & a TMCC Berk jr. The E-33 ignores all the 1033's. Except an occasional short blat.

 

 I have the 80s-90s "grey dial" 80w "modern" controller(#?). It worked every electronic horn I have put to it. But without the 5v voltage boost, no PW work(zero).

(It has decent power, but a fast draw with some Pulmors will make it "drop out". A dual Pulmore GG-1 with a good load, is just too much for it out of the hole without real caution and some luck.

 

I have a very nice kw rebuilt in the late 90s. I don't know what was used yet, but it operates everything great. I can almost quill pw with it.

 

I have but diodes in ZWs, mixed reviews (their request, I had disks)

 

The final quark? No matter the method, the Tmcc bells always work when the track leads are reversed . I'm at speed, way to often for that to be on much.  

 

 I would search around here, and think about building one out of two strings of heavier diodes like say.....Dale H has.