MTH Ditch Light replacement

jasonwncOGR Forum Member

So I've had a bulb finally go out. I've got a RK SD70ACe with a bad ditch light bulb. Now I'm pretty good with electronics and soldering so I figured I'd just buy some grain of wheat bulbs and clip/solder and be done. However, after further inspection, both lead wires are black, how am I supposed to know which is pos and neg? Does it matter? Also, I'm assuming these are 18v 3mm grain of wheat bulbs, is that correct? Should I just order a new bulb with cable from MTH? Any tips before I begin this endeavor? Also, I'm probably going to just go with grain of wheat bulbs instead of swapping out both for LEDs, since I only have the one to replace.

Thanks,

Jason

11/4/1410:31 PM

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Engineer-JoeOGR Forum Member SUPPORTING MEMBER

Nope, they are six volt. + or- does not matter there. It doesn't have a socket.

This is PS2 inside right? PS3 has LEDs.

11/4/1410:43 PM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Anyone that does MTH repairs probably has a box of these. As long as you can solder, email me your address and I'll send you a couple with pigtails, you can solder them to the existing wiring.

11/5/149:55 AM

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prrhorseshoecurveOGR Forum Member DIGITAL SUBSCRIBER

can led's be substituted for the bulbs?

11/5/1411:22 AM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

Yep, just use a 220 ohm resistor in series, the PV lead is the positive side.

11/5/1411:33 AM

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jasonwncOGR Forum Member

Engineer-Joe,

Yes PS2. Six volt, didn't see that one coming. Glad I haven't purchased anything yet. My cursory search hasn't yielded any decent results yet.

John,

THANK YOU, you just saved me the hassle of trying to find a place to get these. I'll email you my address. If you have a PayPal account, I don't mind giving you something for your trouble and stamp

I think I *might* "one day" convert the couple of modern diesels that I have to LEDs, but I wouldn't want to start that effort until well after the holiday season. Which is when my trains get the most use. In fact, I need to read up on best practices on oiling these engines. Since I've only been in the hobby for a couple of years at most I haven't had to do a lot of preventative maintenance yet.

11/5/141:08 PM

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jasonwncOGR Forum Member

John,

Forgive my ignorance, but what do you mean by "PV lead"?

11/5/141:10 PM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

My bad, I should have explained. The PV lead is the positive voltage lead, the negative side is switched by the board. It's normally purple, though that's not chiseled in granite. There will be one lead that is common to both ditch lamps, that's the PV (positive) side.

11/5/141:29 PM

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jasonwncOGR Forum Member

Oh, thanks. So if you want, you can just one resistor for the two bulbs?

11/5/141:35 PM

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gunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

You could put the 220 ohm in series with the PV lead and use a single resistor. The lights may dim a bit when both are on, but I doubt it'll be that noticeable.

Note that for the incandescent bulbs you don't use resistors, just for the LED replacements.

11/5/141:44 PM

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stan2004OGR Forum Member

GRJ, so here I go again imagining you including a couple warm-white 3mm LEDs and 220 ohm resistors in your package. Would be good to document issues installing 3mm LEDs with their "stiff" leads vs. original flexible wires to MTH 6V bulbs in RK ditch lights.