This Forum-thread has discussed possible methods of quieting the buzzing of the Lionel electromechanical E-Unit — either by inserting mechanical dampening, or by converting its powering from AC to DC.
On the assumption that one wants to keep the electromechanical E-Unit (rather than replacing it with a modern electronic reverse unit), there is another approach for quieting the electromechanical E-Unit, and that would be to automatically power it "Off" immediately after cycling it to the next position of its rotary switch. When it has been powered "Off", it is completely silent.
The circuit shown below can silence the E-Unit each time after pulsing it to its next rotational state. Because of its size and complexity, this circuit may not of practical interest or value for most O-Gaugers, but it is at least of theoretical interest, and perhaps it may induce others who are more qualified in designing electrical circuits to create a simpler, smaller, improved version. So the following is offered mainly to spark ideas.
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By inserting the circuit described below into the E-Unit's power-feed, the following is possible:
On the assumption that one wants to keep the electromechanical E-Unit (rather than replacing it with a modern electronic reverse unit), there is another approach for quieting the electromechanical E-Unit, and that would be to automatically power it "Off" immediately after cycling it to the next position of its rotary switch. When it has been powered "Off", it is completely silent.
The circuit shown below can silence the E-Unit each time after pulsing it to its next rotational state. Because of its size and complexity, this circuit may not of practical interest or value for most O-Gaugers, but it is at least of theoretical interest, and perhaps it may induce others who are more qualified in designing electrical circuits to create a simpler, smaller, improved version. So the following is offered mainly to spark ideas.
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By inserting the circuit described below into the E-Unit's power-feed, the following is possible:
- By changing the center-rail power from "Off" to "On", the E-Unit will be pulsed one time; and after that pulse, the E-Unit will become "dead" (unpowered) and silent.
- Pressing the Direction button on the transformer, holding it depressed for about 3 seconds, and then releasing it will send another pulse of power to the E-Unit, after which it will again go "dead" and silent.
I have installed this circuit into a Lionel #601 NW2 Diesel Switcher, and it works relatively well, either with pure sine-wave AC (e.g. from a Lionel 1044 transformer) or with pulse-width-modulated ("chopped") AC (e.g. from a Lionel ZW-c transformer).
The schematic of the circuit is shown below in the attachment.
How the Circuit Works
As manufactured, the "to-be-grounded" wire from E-Unit's coil goes to the "E-Unit Switch".
- When the E-Unit Switch is "On", it "grounds" the wire from the E-Unit's coil to the locomotive frame; this completes the coil's electrical circuit, and the E-Unit operates (and buzzes),
- When the E-Unit Switch is turned to "Off", then the circuit is "opened", and the E-Unit becomes completely dead.
In the circuit shown below, the E-Unit's "to-be-grounded" wire is connected also to the switching pole of a Relay. When the standard E-Unit Switch is turned "Off", then only the Relay contact can operate the E-Unit.
The Relay is powered "On" only when a Darlington transistor-pair (T1 in the diagram) is conducting current (through its collector-to-emitter path).
- T1 drives current through the Relay coil only when current is flowing into its base from capacitor C3.
- Capacitor C3 will pass current into the base of T1 only while C3 is charging.
- When C3 has reached a virtually charged state, it no longer passes sufficient current into the base of T1 for sustaining its collector-to-emitter flow.
- When the base of T1 no longer receives sufficient current from C3, T1 stops conducting.
- When T1 stops conducting, the Relay drops out.
- When the Relay drops out, the E-Unit also drops out and makes no further buzzing or humming sounds.
- C3 will remained charged until center-rail power is interrupted. For whatever duration C3 remains charged, the E-Unit remains "dead".
- When center-rail power drops to "Off", then capacitor C3 gradually discharges its stored energy through resistors R2 and R3. It can take 2-4 seconds for the voltage level on C3 to drop to a level of "emptiness" that will make it ready for pulsing power again into the base of T1 when center-rail power again goes "On".
Comments and Notes:
1) The Optional Switch shown in the schematic allows this circuit to be turned "On" or "Off". With this Optional Switch, 3 states are possible.
- E-Unit Switch "On" (and Optional Switch either "Off" or "On") → → E-Unit operates in its traditional (unmodified) "buzzing" manner.
- E-Unit Switch "Off" and Optional Switch "On" → → E-Unit receives a single pulse of power when power is applied to the center rail, and then goes "dead" (silent). It cannot be pulsed again until after center-rail power has been "Off" for a few seconds.
- E-Unit Switch "Off" and Optional Switch "Off" → → E-Unit is "dead"; doesn't operate at all; directional setting is "locked".
2) Diodes D1, D2, D3, and D4 form a full-wave bridge rectifier for supplying DC to the circuit.
3) The circuit uses polarized components (diodes, electrolytic capacitors, and transistor); when building the circuit, the polarized components must be connected in the correct orientation.
4) The values of the capacitors and resistors were determined by trial-and-error experimentation. An electrical engineer may be able analytically to determine better values. The larger the capacitance of C3, the longer it can pass current into T1, and the longer it will take to be discharged. The higher the values of R2 and R3, the greater the amount of time required for discharging C3.
5) The number and the size of the components make the physical dimensions of this circuit inconveniently large and hard to fit into small spaces. It will probably fit into diesel locomotives. It will not fit into steam locomotives and may not fit even into the tender; but if the tender does have enough space, then the circuit could be placed in the tender, with a tether wire going to the E-Unit Switch in the locomotive.
6) If the locomotive will be powered only by Post-War transformers which apply a simple sine-wave output to the tracks (i.e. no electronic solid-state "switching", "chopping", "pulse-width modulation"), then some of the capacitors can be eliminated from the circuit (or reduced in size) to reduce spatial bulk.
- It is only "chopped" AC that requires such heavy capacitative filtering (without which the "staticky" spikes of "chopped" AC come through as "chopped" DC and cause C3 to stutter rather than to smoothly reach a stable charged state.)
- I tried to use a voltage regulator to smoothe out the rectified DC, but even that seemed ineffective without the capacitors.
/Ralph Platz
