Time to replace a Lionel KW transformer?

In that case I would consider an MTH Z4000, or a Lionel ZW and keep the KW for switches/ accessory power.

Another option would be the MRC AH601 Pure Power Dual, it has a true 270 watt output.  It's a very robust unit and with nice volt and amp meters.

I would just have the KW repaired. I don't know of any modern transformers that will cut in any compensating voltage for your post war whistle motors. (Someone can correct me if I am wrong.) Blow a postwar whistle with a modern transformer and your train will really slow down and lights will dim. Your KW, when working properly will supply a few extra volts to help power the whistle motor when you twist the whistle lever. If your lucky, only the contacts in the KW will need to be cleaned.

If you replace the rectifier disc with a stud rectifier you will be amazed at how well the whistle works.

Jeff Noll posted:

I would like to pick your collective brains for a minute.  My Lionel KW isn't cutting it anymore.  The main issue is the whistle lever.  Engaging it dims the train lights which is especially obvious with passenger trains.  With newer electronic whistles (especially my Williams/Bachmann Berkshire's True Blast) engagement is very "iffy" and considering the lack of a bell button it seems like time to invest in some newer technology.  My friend has a MTH Z-1000 which seems to work well.   I have no plans to go into the hand held controller world.  I will be running  Pre and Post War Lionel, Modern Lionel, Williams and MTH/Railking locomotives in conventional mode one at a time on a single track.  I do not want to buy another transformer after this but don't want to say price isn't a consideration (it is not) but what are your thoughts or recommendations?

I vote for the Z-1000. See if you can borrow your friend's unit for a day or two to be sure you like it. If you need two throttles, the MRC AH601 Pure Power Dual that GRJ mentions above is a good choice, or just use two of the Z-1000s.

Keep the KW and get some Lionel 5906 buttons. 

Rod Miller

Sounds like the contacts which engage the 5 volt auxiliary power have gotten dirty.   I would get the KW cleaned and overhauled.

areizman posted:

If you replace the rectifier disc with a stud rectifier you will be amazed at how well the whistle works.

Can you elaborate on the "stud rectifier" please?

Thanks

-Jim

Well, I did some extensive testing today.  What prompted my thoughts to get a newer transformer was I put my Williams Berkshire with True Blast II on the track and could only get a whistle fart (inaudible buzz) out of it.  I thought I blew-up the True Blast (this loco needed a new true blast when I got it).   If I carefully levered the whistle over just until it made connection it worked fine????  Also, for some reason this engine caused a voltage drop as the lights dimmed significantly and it slowed.  It is electronic so there is no current drain but some compatibility issue exists in the transformer.  A post war Lionel engine I ran (a 675) whistle worked fine also.  My two Railking locos with ps-1 also functioned perfectly.  So I go back to the Williams engine.  It used to work fine (whistle and bell)  and now is very touchy so what changed???   I suppose for the +$100 it would cost for a Z-1000 I should just forget the Williams? 

bigo426 posted:

I would just have the KW repaired. I don't know of any modern transformers that will cut in any compensating voltage for your post war whistle motors. (Someone can correct me if I am wrong.) Blow a postwar whistle with a modern transformer and your train will really slow down and lights will dim. Your KW, when working properly will supply a few extra volts to help power the whistle motor when you twist the whistle lever. If your lucky, only the contacts in the KW will need to be cleaned.

Keep the Kw and have modern diode installed. For the record, my MTH Z1000 blows post war whistles BETTER than any transformer I have.

Rob

Who overhauls KWs in Southern California?

Stud diode. A little cramped in the KW, but can be done.

 So I go back to the Williams engine.  It used to work fine (whistle and bell)  and now is very touchy so what changed???

Sometimes postwar transformers have trouble controlling modern era whistles and horns. This can be caused by the transformer providing insufficient DC bias. When you move the handle partway, the track power is 1/2 wave DC - plenty of DC to operate the electronics, but at the cost of useable voltage to operate the train. The transformer was never intended to be used with the handle in this position.
When the handle is moved all the way to its proper position, a resistor is placed in parallel with the rectifier disk. So most of the power goes through the resistor, with just a little going though the rectifier to keep the relay (or electronic circuit) activated.

The amount of DC bias is related to the load on the transformer. If your Williams horn won't blow, try increasing the load on the transformer. Make the train longer. Or use lighted cars. Or put some incandescent light bulbs on the same terminals as the track. Maybe all three.

Jim Harrington posted:

areizman posted:

If you replace the rectifier disc with a stud rectifier you will be amazed at how well the whistle works.

Can you elaborate on the "stud rectifier" please?

Thanks

-Jim

Sure Jim,

Stud rectifiers are the best replacement for worn out rectifier disks in KW or ZW or other transformers where they will fit. Their shape and design allows them to fit right into the hole where the old disk was. Simply remove the old disk and mount the new stud rectifier into the hole then solder the wire that was on the disk to the post on the new rectifier, Here is a link to the procedure for a ZW transformer however you could easily apply this to your KW.

http://ontracktrestle.com/diode-sell.html

For rectifiers I have used a 1N1183R (or higher number depending on whats in stock). Some say the stud rectifier which is designed for automotive uses is overkill and yes it is. But it fits nicely and easily handles the load.

There are several people who lurk on this forum that rebuild post war transformers. There IS one in California too. Either google it or ask for help here. 

Rob

Found this page:

http://www.tranz4mr.com/KW_Whistle_Diodes.html

That dude is very good and well known. Give him a call.

Rob