Lionel LW transformert

Judd,

Do a general search on the web for Repairing Lionel LW Transformer, then select sites for the Lionel wiring schematic and repair /trouble shooting information.

Found problem with direction button, Apparently put together with arm resting on top of contact instead of beneath it .Pressing button would not break connection to post u. I found a diagram on line shows anode of diode connected to horn switch, mine has  cathode to switch.? Diode checks good and is marked 6 amps.

The stock LW has the traditional diode polarity reversed when A is common and U is variable. It should also be noted that Lionel was not known for accurately portraying the diode polarity on all the service documents. Polarity of the diode did not matter until much later when the bell control was introduced - this edified the positive offset for the horn/whistle and a negative offset for the bell.

Does it look correct in the picture? looks like they cut the disc diode mount down to a tab to solder the diode to. The resistor wire checks ok, and the transformer windings are good also.

A tip on tabs I learned here was use a slodering gun/iron to anneal/ soften  metal tabs before bending. It was concerning tinplate, but should help if you have a heavier iron/gun for the thicker tabs.

   Once it has it's switch issues cleared up, try a newer loco. If you get bell, reverse the diode if you want. If you run just post war, "all aboard".

Would be nice to have it wired correctly before putting it back together, hate to have twist those old tabs to many more times. If I understand it right a positive dc voltage is applied to blow the horn and a negative dc voltage rings the bell? So to get a positive dc voltage the anode of the diode should connect to the transformer winding and the cathode should run to the whistle switch? Does the resistor wire connect to the anode or cathode of the diode? looking at the switch it appears that the diode makes contact before the resistor wire, is that correct?

The issue is that either polarity is "correct".

Correct, as in stock, has a negative offset with A as common. This will operate a bell instead of horn/whistle on newer locomotives (older locomotives manufactured prior to the introduction of bell control will operate a whishtle/horn in this either configuration).

Correct as in following convention has a positive offset with A as common. This will operate the horn/whistle on newer locomotives (and older locomotives).

Below is the wiring diagram. Orient the diode to your preferred "correctness".

So regardless of which way diode is installed pressing the whistle button will only operate the the horn or whistle,even in locomotives that have both bell and whistle?  I did not know that. thanks Judd

Judd, re-read what I wrote:

bmoran4 posted:

...

Correct, as in stock, has a negative offset with A as common. This will operate a bell instead of horn/whistle on newer locomotives (older locomotives manufactured prior to the introduction of bell control will operate a whishtle/horn in this either configuration).

Correct as in following convention has a positive offset with A as common. This will operate the horn/whistle on newer locomotives (and older locomotives).

...

Now  I'am lost ! I would like it to blow the horn or sound the whistle , not ring the bell. I also can see that on this transformer posts A are marked as common and post U is the out put to center rail, not like most others where post U is used as common.

Your statement indicates you want to wire the transformer "correct" as in following the positive offset convention. That will activate the whistle/horn on all locomotives equipped. There will be no activation of the bell. Simply reverse the diode from the stock configuration. This would have the cathode stripe/band towards the switch as you photographed above.

Bingo!

Judd posted:

...I also can see that on this transformer posts A are marked as common and post U is the out put to center rail, not like most others where post U is used as common.

Most Lionel transformers have something other than "U" as common, usually "A", or "B" for lower voltage ranges. Actually, all of the single train transformers are built this way.

The "U" common scheme is reserved for multi-train transformers and there aren't as many of them - V, Z, VW, ZW, KW, SW.

The Type R is an unusual two-train transformer all its own.

bmoran4 posted:

... This would have the cathode stripe/band towards the switch as you photographed above.

That is the correct, stock orientation.

It was determined some years back that many of the pictorial diagrams from the Lionel service literature for transformers had the wrong illustration for diode orientation and that for whistle/horn keep the cathode toward the track center rail.

Thanks for the info, my other transformers, a KW and a ZW  both have posts U as common. I bought them both already serviced and with new diodes. Both work great no problems with whistle and are very quiet. I bought this one for my work bench and it seemed liked a good price. Can you tell from the picture if the resistor wire is connected right ? It runs from the anode side of diode to the whistle switch. thanks again Judd

It appears to be connected properly.

Put every thing back together and tried it again. direction button works fine now. Pressing the whistle button blows the horn but holding down more than a second will stop the engine, pressing it  again will reverse the direction of engine .  I should mention that the engines I've tried have been upgraded to ERR ac commander and rail sounds. I put them on my layout and tried them in conventional mode,  power by Zw the horns worked fine with no effect on direction of engines. I have no prior experience with an LW , so maybe it works that way.  Doesn't matter any way as I  run in command mode only.  Thanks for the responses,  Judd

Postwar Lionel transformers send extra power to the track along with the half-wave DC from the diode when the whistle control is engaged.  This is done to make up for the extra power that the relay and whistle motor use on startup.  On some transformers, a second stage cuts down the extra voltage.  What happens when you 'feather' the whistle button (only hold it down halfway)? 

Mitch 

If I press the button fast all the way down it works fine. Pressing the button slow will first blow the horn then stop engine. Must be in the whistle switch , worn or dirty contacts. I'am going to get a can of electrical cleaner and give it a good spray.  Thanks  Judd

Before spraying, you may wish to try this method:

1 - take an index card or business card and slide it between the contacts. You may need to work the whistle button to get the card in. Then work the button a few times and slide the card to burnish the contacts.

2 - if that does not resolve the problem, moisten a fresh card with a little mineral spirits and try again.

Not too long ago a fellow poster wrote that his LW whistle switch had excessive wear. I think he resolved his issue by bending the contacts. Something I am very reluctant to do, because bending the contacts can cause them to hang up, making things worse.