# Lionel RW Transformer Whistle Diode Question



## SoShoresGuy (Jan 23, 2013)

Background: Pre War locomotives (259E, 238E) and Whistle Tenders (1689W).

I have an RW 110 that has a cranky whistle assembly. Sometimes I get the brief 1.1 V DC and sometimes not, maybe around 4 - 5 V DC, and not enough to energize the whistle armature on the tenders.

I was reading on how to replace the rectifier disk with a 6A10 Rectifier Diode (6A 1000V). The poster of the instructions basically bypassed (removed) the resistance wire circuit. 

Do I need to keep the resistance wire in the circuit, replace it with a resister or am I okay just bypassing the resistance circuit completely like the OP did? Remember, I am running pre war exclusively.

TIA


----------



## Millstonemike (Aug 9, 2018)

The initial partial rotation of the whistle control inserts in series an additional 5 V AC winding, rectified to DC, in series with the AC track voltage. That is used to close the whistle's DC relay. The full rotation inserts the resistor. That's to extend the life of the whistle relay's coil by limiting current on the already closed relay.

Intermittent voltages may not be the rectifier. It may be the whistle control's contacts. I'd check the contacts and the mechanism prior to replacing the rectifier/resistor. You can try: (1) partial rotation to see if you can get the full rectified voltage before the resistor is inserted at full rotation: and (2) pressing/holding the whistle lever at various angles to see if you can get a consistent 5+ V DC. That would indicate a mechanical/contact issue with the control. I had to tighten up the lever mechanism on my 1033 for the whistle control to work reliably. The rectifier and resistor were fine.

Here's a *Link* to Olsen's service manual for the RW (1st page depicted below).


----------



## T-Man (May 16, 2008)

I did one and cannot find the thread. I suggest to search include ZW and KW or the diode size. I am sure you tube has one too.


----------



## SoShoresGuy (Jan 23, 2013)

T-Man said:


> I did one and cannot find the thread. I suggest to search include ZW and KW or the diode size. I am sure you tube has one too.


This is the link I am referring (I don't know if I am allowed to link to outside sources): https://dfarq.homeip.net/replace-a-lionel-rw-rectifier-disc-with-a-diode/


----------



## SoShoresGuy (Jan 23, 2013)

Millstonemike said:


> ... (snip)
> Intermittent voltages may not be the rectifier. It may be the whistle control's contacts. I'd check the contacts and the mechanism prior to replacing the rectifier/resistor. You can try: (1) partial rotation to see if you can get the full rectified voltage before the resistor is inserted at full rotation: and (2) pressing/holding the whistle lever at various angles to see if you can get a consistent 5+ V DC. That would indicate a mechanical/contact issue with the control. I had to tighten up the lever mechanism on my 1033 for the whistle control to work reliably. The rectifier and resistor were fine.
> ... (snip)


I have cleaned the contacts, the one on the right is almost always covered up, but I did use some quick dry electrical PCB cleaner on them. The RW has a plunger bar to move the contacts, not a rotational assembly. The bar that moves the contacts up and down seems quite secure, no wobble whatsoever. That's the reason for replacing the disc with a diode. I just want to know, if I do that, must I keep the resistor circuit or can I bypass it? Thanks for your input.


----------



## Millstonemike (Aug 9, 2018)

SoShoresGuy said:


> I have cleaned the contacts, the one on the right is almost always covered up, but I did use some quick dry electrical PCB cleaner on them. The RW has a plunger bar to move the contacts, not a rotational assembly. The bar that moves the contacts up and down seems quite secure, no wobble whatsoever. That's the reason for replacing the disc with a diode. I just want to know, if I do that, must I keep the resistor circuit or can I bypass it? Thanks for your input.


Can't answer the resistor question. You just don't know how much the whistle coil can take (e.g., grand kid leaning on the whistle for a minute, button gets stuck, etc.). You just don't know.

You could insert the new diode and leave the original resistor? And replace or bypass the resistor later if need be.

Digi key, an electronics supplier, can provide the diode and the resistor for a of couple bucks. And shipping on an order for a few small parts is <$4. I get my stuff in 2 or 3 days.

A 6A 1000V diode and a 51 or 56 Ohm 10 W resistor. If you need help navigating Digikey to find the two components, let me know.


----------



## SoShoresGuy (Jan 23, 2013)

Millstonemike said:


> Can't answer the resistor question. You just don't know how much the whistle coil can take (e.g., grand kid leaning on the whistle for a minute, button gets stuck, etc.). You just don't know.
> 
> You could insert the new diode and leave the original resistor? And replace or bypass the resistor later if need be.
> 
> ...


I already have the diode. I'll keep the resistor wire in the circuit since when the whistle button is fully depressed it uses the resistor circuit. I'm guessing the 1.1 V DC circuit to close the whistle relay (armature) and then uses the resistor circuit to drop the V DC down to ~5. If I need an actual (real) resistor I'll add it later or if not needed at all, I'll remove the circuit.

OT: The rectifier disk looks like an inert metal washer. How can something this simple go bad?


----------



## rkenney (Aug 10, 2013)

SoShoresGuy said:


> OT: The rectifier disk looks like an inert metal washer. How can something this simple go bad?


Here's a picture of a good rectifier disc (right) beside a bad one. In the left shot you can even see the four indentations made by the tension clip that held it in place.









Here's a shot of the voltage (half wave) created when the whistle lever is engaged.


----------



## SoShoresGuy (Jan 23, 2013)

Yep,

I replaced the rectifier disc with a 6A10 diode and bypassed the resistor wire and now I have too many continuous DC Volts (~9 +-) when the whistle button is fully depressed. I'll add a resistor circuit to help drop the DC Volts down to ~.5 after the initial DC Voltage to close the relay armature on the whistle tender. 

PS: The RW whistle wiring is kind of different from the 1033, KW and ZW, so it took a little research and trial and error to figure this out.

Thanks for your help, folks.


----------



## ERIE610 (Jan 19, 2015)

*BASIC ELECTRONICS*

Lionel Engineers designed the Whistle circuit to include Resistance wire. The Resistance wire, as it's name implies, resists the amount of voltage coming thru the circuit. That resistance plus the resistance across the rectifier disc or Diode brings the voltage down to the correct level need to run the Whistle circuit within Lionel Specifications. I would just replace the Rectifier Disk with the Diode and see what happens.

LATER


----------



## Millstonemike (Aug 9, 2018)

The RW resistor replacement part # at traintender.com.


----------



## SoShoresGuy (Jan 23, 2013)

I'm pretty sure that that resistor is for the bulb circuit. From searching, I found that a 1.8 Ohm - 10 Watt resistor is what I need to replace the resistance wire.
I would have kept the resistance wire, but when removing the rectifier disc (disk?), the whole assembly of the rectifier and resistor wire and wire rounds were excluded on the RW transformer.
I am expecting some 1.8 Ohm - 10 Watt resistors soon, so I will hopefully document what I ended up with.
Of course, the diode cut the AC in ~half, without the resistance wire. I Gerry Rigged the resistance wire assembly into the circuit with the diode and I got the expected results of ~22 V AC and ~ 3 V DC on half depression of the whistle button and ~.5 V DC at the full depression.
Thanks.
PS: I fried the original diode when soldering it or operating it. With a new diode, I got the expected results. Sorry for the confusion and miscalculations.


----------



## Millstonemike (Aug 9, 2018)

SoShoresGuy said:


> I'm pretty sure that that resistor is for the bulb circuit. From searching, I found that a 1.8 Ohm - 10 Watt resistor is what I need to replace the resistance wire....
> 
> PS: I fried the original diode when soldering it or operating it. With a new diode, I got the expected results. Sorry for the confusion and miscalculations.


Your right, my bad. I had to review four different service manuals before it became clear.

Solid state doesn't like heat. Its best to "tin" the diode lead quickly and let it cool. Then tin the other connection: wire, lug, etc. Then you can solder the two pre-tinned parts very quickly. Also, a heat sink between diode and the end of its lead helps; needle nose, forceps, etc.


----------



## T-Man (May 16, 2008)

I found a you tube video on diode replacement


----------



## SoShoresGuy (Jan 23, 2013)

T-Man said:


> I found a you tube video on diode replacement


Thanks, T-Man.

This might be a TL;DR, so skip if I babble too much.
The RW uses the same components as the ZW and KW transformers, but it is wired and integrated differently. I researched about using a stud diode in the RW, but there really isn't any place to put one so I have to use a barrel - through hole - diode (6A10-T).
Here is what the original (factory) setup is on my RW: 









The AC power wire and the resistance wire are attached to the plate at the top right solder blob. The other end of the resistance wire is soldered to the lower post on the whistle button "plunger" on the right (Very hard to see in the photo) and is connected to the lower copper contact on the left of the plunger, and the rectifier / stud is attached to a copper "bar" behind the Bakelite that connects to the large copper contact on the right (hard to see). When the whistle button is initially depressed, the contacts cause the AC circuit to go through the rectifier and create the 1.~ (whatever) DC volts to close the whistle armature and increase the AC volts to ~22 +-. When the whistle button is fully depressed, the combination of the rectifier and resistance wire drops the DC volts to ~.5 and keeps the AC volts to ~22 +-.

When I take off the speed nut on the rectifier, the whole assembly comes off, with only the AC and resistance wire holding it in on. There is a copper "bar" that the rectifier stud is connected to, which I think I mentioned earlier. Here is a photo of the rectifier assembly parts and the copper bar that is raised up to expose a soldering area:
Rectifier parts (R-L) Stud, Insulator, Plate w/resistor wire/ Rectifier disc, and Speed Nut (I don't know why the forum wants to flip this photo):









Here is a photo of the copper bar that the rectifier stud is attached to:









This is not my transformer but the OP of the blog I was following. He has reverse polarity on the diode. It shouldn't make a difference on pre-war or early post war locomotives, since the diode supports reverse flow of 1000V, it just cuts off half of the AC wave: 









The OP didn't take the resistor wire or a resistor in consideration. With this setup, the AC volts are cut almost in half, so the locomotive will probably slow down to a craw when the whistle button is fully depressed.

I am planning on putting a resister inline (1.8 Ohms - 10 Watts) but I am also thinking of just replacing the rectifier disc with a nylon fender washer, using all of the other original parts, and connecting one end of the diode to the solder blob on the upper right of the plate (with the AC power wire and resistance wire) and soldering the other end to the speed nut, thereby keeping the original resistance wire.

Thoughts?


----------



## T-Man (May 16, 2008)

Actually I was frustrated with the search engine. There are a few hidden threads on the diode replacement. 

You did a great job on explaining everything. This is a good alternative diode to use. Hope it works out for you.


----------



## SoShoresGuy (Jan 23, 2013)

Okay, this is what I did (if you are interested):

I originally added a 6A10 diode and added another circuit to add a 1.8 Amps resistor. I had to remove the original resistor wire and also solder the diode to the copper bar. This worked but it was a real cluster wiring mess (See previous posts).

This time, I took a different approach. I removed the rectifier disk and replaced it with a rubber fender washer (a nylon washer might be better). Then, I soldered a 6A10 diode (anode end) to where the AC power goes to the rectifier disk and the cathode end to the original speed nut that was attached to the rectifier disk (it connects to the copper bar). 
Photo attached:








I didn't need to remove the resistance wire, mess around with the copper bar and it kept things quite simple.
Viola, ~1.6 (+-) VDC to close the relay and ~.6 VDC constant volts to keep the relay closed. ~22 VAC during this process to keep the whistle armature turning when the whistle button is held down.

Yeah, my soldering techniques need to be improved, but this works and it requires minimal disruption of the RW wiring. I should have done this from the beginning, but the experience I learned helped a lot.

I hope this help other folks out.


----------



## Millstonemike (Aug 9, 2018)

SoShoresGuy said:


> Okay, this is what I did (if you are interested): ...
> 
> Yeah, my soldering techniques need to be improved, but this works and it requires minimal disruption of the RW wiring. I should have done this from the beginning, but the experience I learned helped a lot.


Many times it is easier to "tin" the parts individually (i.e. get the solder to flow on them) and then solder the parts together. That's a go-to approach when working with semiconductors that don't like heat (though the whistle diodes are pretty resilient in that regard, more for smaller stuff, LEDs, etc.).


----------



## SoShoresGuy (Jan 23, 2013)

Millstonemike said:


> Many times it is easier to "tin" the parts individually (i.e. get the solder to flow on them) and then solder the parts together. That's a go-to approach when working with semiconductors that don't like heat (though the whistle diodes are pretty resilient in that regard, more for smaller stuff, LEDs, etc.).


Yep. I got carried away and didn't tin the leads on the diode. I should have, I know. I knew this had a 99.9% of success and hurried. Next time...

Thanks for your input. I appreciate it.


----------



## donerwin (Feb 25, 2021)

SoShoresGuy said:


> Okay, this is what I did (if you are interested):
> 
> I originally added a 6A10 diode and added another circuit to add a 1.8 Amps resistor. I had to remove the original resistor wire and also solder the diode to the copper bar. This worked but it was a real cluster wiring mess (See previous posts).
> 
> ...





SoShoresGuy said:


> Okay, this is what I did (if you are interested):
> 
> I originally added a 6A10 diode and added another circuit to add a 1.8 Amps resistor. I had to remove the original resistor wire and also solder the diode to the copper bar. This worked but it was a real cluster wiring mess (See previous posts).
> 
> ...


This seems to be the solution I need for a different bit of hardware, namely the 166 Whistle Controller. I've obtained the 6A10 diode and hope to replace the rectifier disk with a nylon washer as you did. My wiring is a bit different from the transformer you repaired, and I an not sure where the diode should be inserted into the circuit. Here are a few pics of the existing rectifier setup and the schematic from Lionel Service Bulletin SB-104. (First time posting here - hope the pictures are useable.)





















There are three wires attached to the speed nut. One from the resistor coil. One that goes to the main circuit to the "out" post. And one to the transformer. So I am not sure which wires the diode. should go between. Any suggestions?


----------



## SoShoresGuy (Jan 23, 2013)

The disc and the diode perform the same function, convert AC to DC. I would just replace the disc with the diode. Remove the disc and place the diode between the transformer and the speed nut (or where the other wires are attached) and hope that the smoke doesn't escape from the whistle controller. Good luck. Maybe gunrunner john can add his $.02 since he seems to be the electrical expert in this forum. PM him with your question wouldn't be a bad idea.


----------



## donerwin (Feb 25, 2021)

SoShoresGuy said:


> The disc and the diode perform the same function, convert AC to DC. I would just replace the disc with the diode. Remoe the disc and place the diode between the transformer and the speed nut (or where the other wires are attached) and hope that the smoke doesn't escape from the whistle controller. Good luck. Maybe gunrunner john can add his $.02 since he seems to be the electrical expert in this forum. PM him with your question wouldn't be a bad idea.


Thanks! I appreciate the reply.


----------

