Lionel ZW transformer does supply DC in position 2

[TCH]

Greetings, I'm new to the forum but have found good information on general google searchs. Forgive me if this post is in the wrong place.

I've replaced the diode in my ZW as the whistle controller wasn't delivering sufficient  DC. Now I get lots of DC in position 1 and zero DC in position 2. 

The Nichrome resistor is currently connected to the switch ground plate and the second controller position.

I've seen mixed advise on adding or reducing resistance at this point to increase Whistle position 2 DC output, perhaps impacted by the diode vs selenium rectifier.

The question should I add resistance or reduce it and is this the correct strategy?

I've seen several posts that 2nd position DC doesn't work for ZW owners after diode replacement. Many thanks, Tom

 

[lionelsoni]

I suspect you have some wiring error, but I don't have any ZW transformers, so I can't help you with that.  I can give you some general advice:

o  The original diode is copper-oxide, not selenium, and has a significantly lower forward voltage than an ordinary silicon diode.  A Schottky diode is a better replacement for copper-oxide.

o  The old Lionel schematics use an odd symbol for the diode, with three connections.  The one that looks like an anode is actually the cathode; and the two diagonal connections on what looks like a cathode are actually the anode and are connected together.

o  If you get the diode connections backwards, the center rail voltage will have a negative DC component.  A whistle relay will operate with either polarity, but a modern locomotive will interpret negative voltage as a bell command, not a whistle command.

[smokey1]

What is position 2. Your ZW has A, B, C, D, in that order. Position B & C ( your controls without the handles ( A & D have the big handles ) don't have whistle control only A & D. 

[TrainLarry]

Position 2 refers to the whistle controls on transformers. The whistle control is a 2 position switch. The first position as you press the whistle switch engages the whistle rectifier to blow the whistle. As you continue to press the switch down, the 2nd switch position is engaged to add the 5 volt compensating winding into the circuit to boost the transformer output voltage, as the air whistles drop the voltage as they blow, and the compensating winding boosts the voltage back up.

 

Larry

[ADCX Rob]

TrainLarry

Position 2 refers to the whistle controls on transformers. The whistle control is a 2 position switch. The first position as you press the whistle switch engages the whistle rectifier to blow the whistle. As you continue to press the switch down, the 2nd switch position is engaged to add the 5 volt compensating winding into the circuit to boost the transformer output voltage, as the air whistles drop the voltage as they blow, and the compensating winding boosts the voltage back up.

Close!  The compensating winding is always in the circuit during whistle activation.

[TCH]

Thanks for the correction. I will replace the 2 ohm resistor with a 1 ohm resistor but I'm not hopeful as I did parallel a 3 ohm and still had a problem. Do you mind sharing what transformers you use these days. Most of my trains are late 90s early 2000s MTH, Lionel and high end Kline.

[Tranz4mr.com]

I've found that the electrical connections to the switch contacts where wires are soldered to the switch tabs and the tabs are riveted to the switch corrode and or loosen up  This adds resistance or intermittent connections causing the second stage of the switch to not work. The fix is to clean the rivet to tab connection with a dremel wire wheel then solder the rivet to the tab. Also check for cracked solder joints where wires solder to the metal switch bracket.  The white nichrome resister wire  has brass crimps at each end. Recrimp these since the connection can oxidize over time. Cleaning switch contacts with contact cleaner also helps.