MTH circuit board lamp voltage ?

The nominal voltage rating of the incandescent bulbs is 6V, and indeed there is a PWM drive to the lamps, it's not straight DC.  The PWM drive is generated on the processor board.

Thank you..i see a lot of gow led's prewired for 12 and 6 volt. Which is best?

Truthfully, I don't use the pre-wired LED's, as I see no value added.  I use a standard LED and a 220 or 270 ohm resistor to replace incandescent bulbs with LED's in PS/2 equipment.  I would presume you could use pre-wired 6V ones, but I have truthfully never seen that particular item offered, they're usually rated for higher voltages.

I have used 150 when powering a series marker set off Bulb circuit and 300ohms when a single LED.

The 6V are out there, believe they are made for older autos and boats with 6V batteries.  I have seen them. 

You need to be careful when taking measurements on PS engines.  AC is not common, though you can get away with it when measuring purple +.  Blue is typically PCB Ground.  Purple is DC positive.  The colored wires are return to PCB ground via FET for PS-2.  G

I'm sure a 6V item exists, I just never needed or wanted one.  I do wonder if a boat item would fit where they need to go in the locomotive.

Technically, for a white LED, you can use 150 ohms, as it's operating voltage is 3V at 20ma.  I don't like to push them to the limit however, and the difference in light output is minimal between 150 and 220.

I just mimic the resistors that MTH used in older CV boards. I said 150 for series markers which are 2 red or green in series.  I use 300 for the single LED.  I change parallel markers to series for PS-2 use.

The LED are small for indicators.  I think that is what they are used for, not lighting the cabin or engine compartment

 Can i use these as replacement LED's.

 http://www.ebay.com/itm/10-x-P...?hash=item25a0866456

You can, but for about 1/10 of the price you can put a 220 ohm resistor in series with a 5 cent LED and get the same job done.  If you're going to solder wires anyway, what's the point of spending all that extra cash for soldering one resistor in a wire?

 Your right..might as well build a stock..do they make the 3 mm without the ridge as it looks like it might hang up in the rubber holder or are they long enough?

I just hit it with a file, the ridge comes right off.   They work fine, I just stick them in until they project slightly and call them good.  Without the ridge, they hand in there pretty good.

Ahhhh...flangeless 3mm but cant decide on warm white or bright white.

http://www.ebay.com/itm/100pcs...?hash=item4ae77d5b43

http://www.ebay.com/itm/1000pc...?hash=item4ac839568e

Flip of the coin for modern diesels, older diesels and steamers I use warm white pretty exclusively.

John, I have a few engines and have never blown a headlight on an MTH loco.  Lionel a few.

I don't worry about them blowing the bulbs, I just like the look of headlights with the focused beam of LED's.  They just look a lot more like real headlights to me.  Other than really ancient steamers that had really weak headlights, looking down the track into the headlight of a locomotive you'll see a very bright light.  IMO, the LED's look much closer to what the prototype looks like.  Obviously, the color temperature is all important, I have several shades of warm white 3mm and 5mm LED's, as well as the bright white.

 I played with several LEDs in my G scale upgrades before I got it perfect for me. I used super bright warm white bulbs with the smallest resistor I dared (180? I think). When the trains are outside at night, they actually look real (scale sized of course). They are tough to look straight into because they're so bright.

 I think they are not really focused and won't look quite like real, but they are darned close now. I didn't like the stock bluish ones that came with the engines (lower photo).

  The nice thing about using LEDs is you can add extras. I put ground lights on the PS2 interior light circuit that look cool to me. I had hoped that the new PS3 MTH G scale releases would start coming with more lighting effects. The MTH O scale Dreyfus I got has some cool lighting.

Good look Joe.

Joe,

 Definitely great looking, real nice set up!

   PCRR/Dave

In replacing the 2 filament number board lights is there enough forward voltage to wire in 2 warm white led's[3.3 forward voltage] in series?

Yep.  Since the lamp drive is PWM at a higher voltage, there is actually enough for three or four in series.  Just use a 100 ohm or larger in series with the two series LED's and it will be fine.

Gentlemen,

    I have come to believe all you Electrical Engineering guys are great people!  Not all sane, but great people.

PCRR/Dave