This is what I do for both Conventional and Legacy/TMCC
First, the output power of an LW is equivalent to an MTH Z-750-- about 75 watts. Each TIU channel is capable of handling 10 amps. The newest versions have fuses inside for each channel. Transient protection is in the TIU. I use a Z-4000 which has excellent overcurrent protection-- it electronically limits the output to 180W, so if you set the output higher than 18v, you get less than 10 amps–
HTH—
It doesn’t much matter where the TVS is located. Its purpose is to clip the voltage spikes that occur when the transformer’s magnetic field collapses after each short circuit, especially the numerous ones that occur during a derailment. You can do that right at the transformer or anywhere between the transformer and the locomotive.
The TVS should be connected between the two sides of the circuit. I don’t see any point to the overpriced ones sold as an assembly that connect one from each side of the circuit to ground.
Remember in sizing your TVS that the normal peak voltage is 40 percent higher than the RMS track voltage, and that it’s good to allow a safety margin above that to account for the tolerance in the TVS’s and the transformer’s voltage ratings.
Thank you to all who have contributed to this discussion about external (external to the transformer) protections.
My LTS suggested I trade in my Type ZW (275 watts) which I got in the mid 1950s for one of their used/refurbished ones, saying it might be more cost effective. At $250-$300 for another used one less my exchange, I’m not so sure.
Other than needing a power cord, the larger/major right hand throttle (most heavily used) seems to have lost its graduating precision 0-12 volts so that operating at lower speeds is at times frustrating to modulate. I run nothing other than postwar. In my terminology, they said the “rheostat windings” are probably worn and need replacing, not just a simple cleaning and adjustment.
I think I will just pay the piper, have them repair it, and keep what I have. This store has always been totally reasonable (price-wise), thorough, competent, and as anal about cosmetics as I am when I have had engines serviced in the past.
Jack
Jack, there is no rheostat in a ZW (or any other Lionel transformer that I know of). The carbon roller rolls over a section of the secondary winding, which is very heavy copper wire in that transformer.and unlikely ever to wear out. If it did, you would need to replace the entire transformer proper inside the “transformer” box. It is likely that your intermittent operation at some speeds is due to a worn carbon roller, which has reduced the pressure with which the roller makes contact with the winding. The fix replacing the roller(s), is a routine repair and no big deal. Cleaning is nothing more than wiping or brushing off the carbon powder left on the winding by the wearing of the rollers and only worth doing if the box is open anyway (to replace the rollers), since the powder isn’t likely to affect operation.
Thanks, Bob. I think I will listen to you, keep it, and get it serviced. I can feel each incremental “click” in the voltage range as the throttle is moved, but some of them don’t seem to add power.
Jack.