Tapping track power for GS-4 MARS light

track power is normally the red and black wires going to the PS board from the pick-ups. That is normally AC right from the rails. So not really constant voltage that is regulated at all. Is this board AC or DC? What are it's limits?

2 other important things here. You should install a choke so that the board shown, doesn't kill DCS signal. You should also state just what GS model you are talking about. PS1, 2 or 3!

https://ogrforum.com/...y-designs-mars-light

The GS-4 is a PS2 engine and the board is for both AC and DC current up to 18v.

A simple power supply will do the trick for a low current device like a MARS light simulator.

Your board looks like a simple power supply with a dropping resistor.  I don't see how that emulates a real MARS light.

One bulb flashes while the other is steady so the headlight sort of pulses from dimmer to bright.  It's the best I could do as I don't have the skill or equipment to solder connections to the tiny PCB that Ngineering makes.  Wish someone would start selling them pre-wired.  Anyway, when you say a "simple power supply", what are you referring to?

You can always get someone to solder the wires onto the ngineering MARS simulator, it's a great little board.  I combine it with a small power supply for anything from track power on down.

Anyway, tested this light board with direct track power (simply touching the leads to the track) @ 12v and it works and looks good.  Now I am lost as to where inside the 4999 PS2 locomotive I can attach the leads to get that sort of direct voltage.  The pickup rollers are on the tender of this particular engine and the wires inside the locomotive are a jumble coming off of the tether.  The existing connections for all the headlights are way too low voltage.  Any info on which wires I can tap to power this board would be helpful.

Normally, track power is on pins 7-8 of the tether.  The "typical" color is black and red.  They're the next pins to the motor wiring (yellow and white).  Check with a meter to see if track power actually comes in on the red wire by plugging the tether in and measuring from a tender roller to the tether connector in the locomotive.

Of course, the actual MTH product number would be useful, you know, the 20.xxxx.1 number?

Your Mars circuit looks hand-built?  Do you have the schematic or any additional information (other than 8-18V AC)?  Or a photo of the back-side if that shows anything?

You say the headlight has 'way too low voltage'.  Is this based on a DC voltage measurement at the headlight connector (probably a couple of Volts or so)?  Depending your Mars circuit, there may actually be enough voltage.  That is, the PS2 headlight circuit is a quirky pulsing voltage and I see a rather large (220uF) capacitor on your Mars board that might be just enough.

Separately, you say that the power pickups are ONLY on the tender.  I wonder though if the 2 power wires are nevertheless brought to the tether and hence available at the connector (shown at left in the following diagram) on the boiler side.  That is, in this wiring diagram from the PS2 Steam Upgrade kit manual, it shows how the 2 power wires are "assigned" to the tether between tender and boiler.  Hopefully one of the MTH tech gurus will chime in if this is relevant to your specific engine.

Stan, if we knew what the actual engine product number was, it would help.

It's a 20-3303-1.  I ended up wiring it to the motor leads and it seems to work fine.  It comes on only when the engine is moving, which I believe is actually prototypical.

I'm confused here. The rollers are on the tender? All Premier GS Northerns have the rollers on the locomotive. Also why replace the MARS light? The locomotive already comes with a MARS light that runs from the PS2 electronics. Did you gut the locomotive and convert the electronics to something else?

Lou, pretty sure only the PS3 version has a MARS light.  This PS2 GS-4 has a four bulb assembly in the smokebox that doesn't flash or anything.   Could someone clarify weather the PS2 has a flashing MARS light effect or not?  The MTH website descriptions only list an operating MARS light effect for the PS3 version.  The socket lead for the the bulb that would be in the top (MARS) headlight position didn't work when I got this engine and I tried several replacement bulbs in it with no results.  Can the MARS be turned off with a remote?  I only run conventional so I didn't have the option.  I'm 99% positive that the PS2 GS-4 doesn't have a MARS light.  Anyway, yes, the pickup rollers are all on the tender, none on the engine itself.

The 20-3920-1 PS1 version I have has the flashing MARS light. It has its own board in the top of the boiler. I left it alone when I did my ERR conversion. I also have rollers pickup on the engine.

@Knight007 posted:

Lou, pretty sure only the PS3 version has a MARS light.  This PS2 GS-4 has a four bulb assembly in the smokebox that doesn't flash or anything.   Could someone clarify weather the PS2 has a flashing MARS light effect or not?  The MTH website descriptions only list an operating MARS light effect for the PS3 version.  The socket lead for the the bulb that would be in the top (MARS) headlight position didn't work when I got this engine and I tried several replacement bulbs in it with no results.  Can the MARS be turned off with a remote?  I only run conventional so I didn't have the option.  I'm 99% positive that the PS2 GS-4 doesn't have a MARS light.  Anyway, yes, the pickup rollers are all on the tender, none on the engine itself.

The PS2 version has a flashing MARS light and pickups on the locomotive, not the tender. Someone has done some extensive modifications to your locomotive at some point....

There's no indication of that.  This is a Daylight, not a Northern.  Additionally, all the PS2 GS-4s on youtube do not have flashing mars lights either.  The places on my GS4 engine where the pickup rollers would normally go aren't even drilled through the frame completely, indicating that rollers were never installed there.  Lastly, the MTH product locator only indicates an "operating MARS light" for PS3 models of the GS-4 Daylight.

@Knight007 posted:

There's no indication of that.  This is a Daylight, not a Northern.  Additionally, all the PS2 GS-4s on youtube do not have flashing mars lights either.  The places on my GS4 engine where the pickup rollers would normally go aren't even drilled through the frame completely, indicating that rollers were never installed there.  Lastly, the MTH product locator only indicates an "operating MARS light" for PS3 models of the GS-4 Daylight.

I own a Premier PS2 GS4 in Daylight paint. It has rollers on the locomotive and a MARS light. Came from MTH this way.

Worst case the MARS light was turned off in DCS. Find someone with a DCS system and see if they can try turning it back on.

Edit. Double checking it looks like some runs had tender rollers where as some did not. Odd. Anyway this GS4 freight set was made the same year as yours: https://mthtrains.com/20-3301-1

Here's a Youtube video of it with a working MARS light:

I'm very certain that your MARS light was either turned off in DCS or is malfunctioning. Since you don't have DCS try this to do a feature reset and see if the MARS light comes on.

@Knight007 posted:

It's a 20-3303-1.  I ended up wiring it to the motor leads and it seems to work fine.  It comes on only when the engine is moving, which I believe is actually prototypical.

Did you have occasion to try hooking it up to the headlight output?  As I mentioned earlier you might have only measured a couple Volts on the headlight output making it appear that there's not enough voltage.  But it's an unusual pulsed voltage that may be enough to operate your Mars circuit.  If it works it would likely work in only one orientation so you may need to reverse the 2 wires.

Of course if you're happy with it operating only when the motor is active then so be it.